Molecules

15 pages, 1339 KiB

Open AccessArticle

α,α-Difluorophosphonohydroxamic Acid Derivatives among the Best Antibacterial Fosmidomycin Analogues

by Aurore Dreneau, Fanny S. Krebs, Mathilde Munier, Chheng Ngov, Denis Tritsch, Didier Lièvremont, Michel Rohmer and Catherine Grosdemange-Billiard

Molecules 2021, 26(16), 5111; https://doi.org/10.3390/molecules26165111 - 23 Aug 2021

Cited by 4 | Viewed by 2657

Abstract

Three α,α-difluorophosphonate derivatives of fosmidomycin were synthesized from diethyl 1,1-difluorobut-3-enylphosphonate and were evaluated on Escherichia coli. Two of them are among the best 1-deoxy-d-xylulose 5-phosphate reductoisomerase inhibitors, with IC₅₀ in the nM range, much better than fosmidomycin, the reference [...] Read more.

Three α,α-difluorophosphonate derivatives of fosmidomycin were synthesized from diethyl 1,1-difluorobut-3-enylphosphonate and were evaluated on Escherichia coli. Two of them are among the best 1-deoxy-d-xylulose 5-phosphate reductoisomerase inhibitors, with IC₅₀ in the nM range, much better than fosmidomycin, the reference compound. They also showed an enhanced antimicrobial activity against E. coli on Petri dishes in comparison with the corresponding phosphates and the non-fluorinated phosphonate. Full article

(This article belongs to the Special Issue Women in Bioorganic Chemistry)

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25 pages, 2982 KiB

Open AccessReview

Membrane Sensor Histidine Kinases: Insights from Structural, Ligand and Inhibitor Studies of Full-Length Proteins and Signalling Domains for Antibiotic Discovery

by Pikyee Ma and Mary K. Phillips-Jones

Molecules 2021, 26(16), 5110; https://doi.org/10.3390/molecules26165110 - 23 Aug 2021

Cited by 12 | Viewed by 4759

Abstract

There is an urgent need to find new antibacterial agents to combat bacterial infections, including agents that inhibit novel, hitherto unexploited targets in bacterial cells. Amongst novel targets are two-component signal transduction systems (TCSs) which are the main mechanism by which bacteria sense [...] Read more.

There is an urgent need to find new antibacterial agents to combat bacterial infections, including agents that inhibit novel, hitherto unexploited targets in bacterial cells. Amongst novel targets are two-component signal transduction systems (TCSs) which are the main mechanism by which bacteria sense and respond to environmental changes. TCSs typically comprise a membrane-embedded sensory protein (the sensor histidine kinase, SHK) and a partner response regulator protein. Amongst promising targets within SHKs are those involved in environmental signal detection (useful for targeting specific SHKs) and the common themes of signal transmission across the membrane and propagation to catalytic domains (for targeting multiple SHKs). However, the nature of environmental signals for the vast majority of SHKs is still lacking, and there is a paucity of structural information based on full-length membrane-bound SHKs with and without ligand. Reasons for this lack of knowledge lie in the technical challenges associated with investigations of these relatively hydrophobic membrane proteins and the inherent flexibility of these multidomain proteins that reduces the chances of successful crystallisation for structural determination by X-ray crystallography. However, in recent years there has been an explosion of information published on (a) methodology for producing active forms of full-length detergent-, liposome- and nanodisc-solubilised membrane SHKs and their use in structural studies and identification of signalling ligands and inhibitors; and (b) mechanisms of signal sensing and transduction across the membrane obtained using sensory and transmembrane domains in isolation, which reveal some commonalities as well as unique features. Here we review the most recent advances in these areas and highlight those of potential use in future strategies for antibiotic discovery. This Review is part of a Special Issue entitled “Interactions of Bacterial Molecules with Their Ligands and Other Chemical Agents” edited by Mary K. Phillips-Jones. Full article

(This article belongs to the Special Issue Interactions of Bacterial Molecules with Their Ligands and Other Chemical Agents)

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18 pages, 1176 KiB

Open AccessArticle

Crop Yield and Essential Oil Composition of Two Thymus vulgaris Chemotypes along Three Years of Organic Cultivation in a Hilly Area of Central Italy

by Basma Najar, Luisa Pistelli, Benedetta Ferri, Luciana Gabriella Angelini and Silvia Tavarini

Molecules 2021, 26(16), 5109; https://doi.org/10.3390/molecules26165109 - 23 Aug 2021

Cited by 16 | Viewed by 3095

Abstract

Thymus vulgaris L. is one of the most commonly used medicinal and aromatic plants (MAPs), owing to a range of therapeutic properties of its essential oil. Plant growth, biomass yield, essential oil content and composition are influenced by chemotype, environmental conditions, cultivation techniques [...] Read more.

Thymus vulgaris L. is one of the most commonly used medicinal and aromatic plants (MAPs), owing to a range of therapeutic properties of its essential oil. Plant growth, biomass yield, essential oil content and composition are influenced by chemotype, environmental conditions, cultivation techniques and vegetative development. Since in MAPs cultivation special attention is paid on high quality of raw material, the adoption of sustainable agriculture methods is of pivotal importance. Therefore, we evaluated the agronomic and qualitative performances of two Thymus vulgaris L. chemotypes, organically cultivated under the Mediterranean climate of hilly lands of central Italy for three consecutive years (2017–2019). Along the trial, total above-ground dry biomass significantly increased from the 1st to 3rd year after planting and large variations in the main biological, biometric and productive traits were observed between the two chemotypes. The ‘thymol’ chemotype EO obviously showed thymol as the major constituent (51.26–49.87%) followed by γ-terpinene and p-cymene. The ‘linalool’ chemotype EO showed high percentages of oxygenated monoterpenes (about 90%) with linalool (75%), linalyl acetate (8.15%) and b-caryophyllene (3.2%) as main constituents. This study highlighted that T. vulgaris can be successfully organically grown in the hilly lands of Tuscany, with interesting biomass and essential oil yields, even though the plants were in the initial years of crop establishment (start in 2017). The introduction of this species into organic cultivation systems could contribute to obtain high-quality raw material, as well as to enhance crop rotation diversification, which is of pivotal importance in the management of organic farms. Full article

(This article belongs to the Special Issue Natural Plant Substances—Structural and Application Aspects: A Theme Issue in Honor of Professor Wieslaw Oleszek)

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15 pages, 2514 KiB

Open AccessArticle

Assessment of Volatile Aromatic Compounds in Smoke Tainted Cabernet Sauvignon Wines Using a Low-Cost E-Nose and Machine Learning Modelling

by Vasiliki Summerson, Claudia Gonzalez Viejo, Alexis Pang, Damir D. Torrico and Sigfredo Fuentes

Molecules 2021, 26(16), 5108; https://doi.org/10.3390/molecules26165108 - 23 Aug 2021

Cited by 22 | Viewed by 3677

Abstract

Wine aroma is an important quality trait in wine, influenced by its volatile compounds. Many factors can affect the composition and levels (concentration) of volatile aromatic compounds, including the water status of grapevines, canopy management, and the effects of climate change, such as [...] Read more.

Wine aroma is an important quality trait in wine, influenced by its volatile compounds. Many factors can affect the composition and levels (concentration) of volatile aromatic compounds, including the water status of grapevines, canopy management, and the effects of climate change, such as increases in ambient temperature and drought. In this study, a low-cost and portable electronic nose (e-nose) was used to assess wines produced from grapevines exposed to different levels of smoke contamination. Readings from the e-nose were then used as inputs to develop two machine learning models based on artificial neural networks. Results showed that regression Model 1 displayed high accuracy in predicting the levels of volatile aromatic compounds in wine (R = 0.99). On the other hand, Model 2 also had high accuracy in predicting smoke aroma intensity from sensory evaluation (R = 0.97). Descriptive sensory analysis showed high levels of smoke taint aromas in the high-density smoke-exposed wine sample (HS), followed by the high-density smoke exposure with in-canopy misting treatment (HSM). Principal component analysis further showed that the HS treatment was associated with smoke aroma intensity, while results from the matrix showed significant negative correlations (p < 0.05) were observed between ammonia gas (sensor MQ137) and the volatile aromatic compounds octanoic acid, ethyl ester (r = −0.93), decanoic acid, ethyl ester (r = −0.94), and octanoic acid, 3-methylbutyl ester (r = −0.89). The two models developed in this study may offer winemakers a rapid, cost-effective, and non-destructive tool for assessing levels of volatile aromatic compounds and the aroma qualities of wine for decision making. Full article

(This article belongs to the Special Issue Smoke Taint in Grapes and Wine)

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Mean values of smoke aroma intensities as rated using a 15 cm intensity scale with the letters of significance from the ANOVA and Fisher least significant difference (LSD) post hoc test (p < 0.05; α = 0.05). Abbreviations: C = control, CM = control with in-canopy misting, HS = high-density smoke exposure, HSM = high-density smoke exposure with in-canopy misting, LS = low-density smoke exposure, SE = standard error. Full article ">Figure 2
Mean stacked values of the electronic nose depicting the letters of significance from the ANOVA and Fisher least significant difference (LSD) post hoc test (p < 0.05; α = 0.05). Abbreviations: C = control, CM = control with in-canopy misting, HS-high = density smoke exposure, HSM = high-density smoke exposure with in-canopy misting, LS = low-density smoke exposure. Full article ">Figure 3
Principal component analysis displaying the e-nose readings (blue), smoke aroma intensity (green) and volatile aromatic compounds (purple). Abbreviations: C = control, CM = control with in-canopy misting, HS = high-density smoke exposure, HSM = high-density smoke exposure with in-canopy misting, LS = low-density smoke exposure. Full article ">Figure 4
Matrix illustrating the significant (p < 0.05) correlations between the sensory parameters, e-nose readings, and volatile aroma compounds. Colour bar: the blue side depicts the positive correlations, while the yellow side depicts the negative correlations. Darker blue and yellow colours denote higher correlations. Full article ">Figure 5
Overall correlations of the two models to predict: (a) the levels of volatile aromatic compounds (Model 1) and (b) levels of smoke aroma intensities (Model 2). Full article ">Figure 5 Cont.
Overall correlations of the two models to predict: (a) the levels of volatile aromatic compounds (Model 1) and (b) levels of smoke aroma intensities (Model 2). Full article ">Figure 6
Two-layer feedforward network for the artificial neural network models developed to predict: (a) the levels of volatile aromatic compounds present in wine (Model 1) and (b) smoke aroma intensity (Model 2). Abbreviations: W = weights, b = biases. Full article ">Figure 6 Cont.
Two-layer feedforward network for the artificial neural network models developed to predict: (a) the levels of volatile aromatic compounds present in wine (Model 1) and (b) smoke aroma intensity (Model 2). Abbreviations: W = weights, b = biases. Full article ">

23 pages, 2887 KiB

Open AccessArticle

Synthesis, In Silico and In Vitro Evaluation of Antimicrobial and Toxicity Features of New 4-[(4-Chlorophenyl)sulfonyl]benzoic Acid Derivatives

by Theodora-Venera Apostol, Mariana Carmen Chifiriuc, Constantin Draghici, Laura-Ileana Socea, Luminita Gabriela Marutescu, Octavian Tudorel Olaru, George Mihai Nitulescu, Elena Mihaela Pahontu, Gabriel Saramet and Stefania-Felicia Barbuceanu

Molecules 2021, 26(16), 5107; https://doi.org/10.3390/molecules26165107 - 23 Aug 2021

Cited by 5 | Viewed by 3153

Abstract

The multi-step synthesis, physico-chemical characterization, and biological activity of novel valine-derived compounds, i.e., N-acyl-α-amino acids, 1,3-oxazol-5(4H)-ones, N-acyl-α-amino ketones, and 1,3-oxazoles derivatives, bearing a 4-[(4-chlorophenyl)sulfonyl]phenyl moiety are reported here. The structures of the newly synthesized compounds were confirmed by spectral [...] Read more.

The multi-step synthesis, physico-chemical characterization, and biological activity of novel valine-derived compounds, i.e., N-acyl-α-amino acids, 1,3-oxazol-5(4H)-ones, N-acyl-α-amino ketones, and 1,3-oxazoles derivatives, bearing a 4-[(4-chlorophenyl)sulfonyl]phenyl moiety are reported here. The structures of the newly synthesized compounds were confirmed by spectral (UV-Vis, FT-IR, MS, ¹H- and ¹³C-NMR) data and elemental analysis results, and their purity was determined by RP-HPLC. The new compounds were assessed for their antimicrobial activity and toxicity to aquatic crustacean Daphnia magna. Also, in silico studies regarding their potential mechanism of action and toxicity were performed. The antimicrobial evaluation revealed that the 2-{4-[(4-chlorophenyl)sulfonyl]benzamido}-3-methylbutanoic acid and the corresponding 1,3-oxazol-5(4H)-one exhibited antimicrobial activity against Gram-positive bacterial strains and the new 1,3-oxazole containing a phenyl group at 5-position against the C. albicans strain. Full article

(This article belongs to the Special Issue Recent Advances in the Synthesis and Biological Studies of Five-Membered Azaheterocycle Derivatives)

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Structures of some representative bioactive naturally occurring compounds containing 1,3-oxazole moiety. Full article ">Figure 2
Structures of some representative bioactive synthesized compounds containing 1,3-oxazole moiety. Full article ">Figure 3
Structures of compounds 3 and 5a,b with the atoms’ numbering (for NMR assignments). Full article ">Figure 4
Structures of compounds 4 and 6a,b with the numbering of atoms (used for NMR assignments). Full article ">Figure 5
Structures of the designed analogs 7a,b and 8a,b. Full article ">Figure 6
Structures of two compounds extracted from ChEMBL which are structurally similar to the compounds 6a and 6b. Full article ">Scheme 1
Synthesis of the new compounds 3–6. Reagents and conditions: (a) SOCl2, reflux, 30 h (99% [<a href="#B67-molecules-26-05107" class="html-bibr">67</a>]); (b) (i) valine/NaOH, CH2Cl2, 0–5 °C, 30 min; room temperature (r.t.), 1 h; (ii) HCl (93%); (c) ethyl chloroformate/4-methylmorfoline, CH2Cl2, r.t., 30 min (93%); (d) C6H5-R (R = H or CH3), AlCl3, r.t., 20 h (5a: 86%, 5b: 90%); (e) POCl3, reflux, 4 h (6a: 90%, 6b: 91%). Full article ">

16 pages, 4386 KiB

Open AccessArticle

Theoretical–Computational Study of Atmospheric DBD Plasma and Its Utility for Nanoscale Biocompatible Plasmonic Coating

by Taj Muhammad Khan, Shahab Ud-Din Khan, Muhammad Raffi and Riaz Khan

Molecules 2021, 26(16), 5106; https://doi.org/10.3390/molecules26165106 - 23 Aug 2021

Cited by 10 | Viewed by 2834

Abstract

In this study, time-dependent, one-dimensional modeling of a surface dielectric barrier discharge (SDBD) device, driven by a sinusoidal voltage of amplitude 1–3 kV at 20 kHz, in argon is described. An SDBD device with two Cu-stripe electrodes, covered by the quartz dielectric and [...] Read more.

In this study, time-dependent, one-dimensional modeling of a surface dielectric barrier discharge (SDBD) device, driven by a sinusoidal voltage of amplitude 1–3 kV at 20 kHz, in argon is described. An SDBD device with two Cu-stripe electrodes, covered by the quartz dielectric and with the discharge gap of 20 × 10⁻³ m, was assumed, and the time-dependent, one-dimensional discharge parameters were simulated versus time across the plasma gap. The plasma device simulated in the given arrangement was constructed and used for biocompatible antibacterial/antimicrobial coating of plasmonic particle aerosol and compared with the coating strategy of the DBD plasma jet. Simulation results showed discharge consists of an electrical breakdown, occurring in each half-cycle of the AC voltage with an electron density of 1.4 × 10¹⁰ cm⁻³ and electric field strength of 4.5 × 10⁵ Vm⁻¹. With SDBD, the surface coating comprises spatially distributed particles of mean size 29 (11) nm, while with argon plasma jet, the nanoparticles are aggregated in clusters that are three times larger in size. Both coatings are crystalline and exhibit plasmonic features in the visible spectral region. It is expected that the particle aerosols are collected under the ionic wind, induced by the plasma electric fields, and it is assumed that this follows the dominant charging mechanisms of ions diffusion. The cold plasma strategy is appealing in a sense; it opens new venues at the nanoscale to deal with biomedical and surgical devices in a flexible processing environment. Full article

(This article belongs to the Special Issue Plasma Technologies and Their Medical Applications)

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28 pages, 14370 KiB

Open AccessArticle

Efficiency of Fe₃O₄ Nanoparticles with Different Pretreatments for Enhancing Biogas Yield of Macroalgae Ulva intestinalis Linnaeus

by Ahmed El Nemr, Mohamed A. Hassaan, Marwa R. Elkatory, Safaa Ragab and Antonio Pantaleo

Molecules 2021, 26(16), 5105; https://doi.org/10.3390/molecules26165105 - 23 Aug 2021

Cited by 39 | Viewed by 3067

Abstract

In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and [...] Read more.

In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and green synthesized Fe₃O₄) and in a combination of the first three mentioned pretreatments methods with magnetite (Fe₃O₄) NPs, (ultrasonic-Fe₃O₄, ozone-Fe₃O₄ and microwave-Fe₃O₄) in different treatment times. Moreover, the green synthesized Fe₃O₄ NPs has been confirmed by FTIR, TEM, XRD, SEM, EDEX, PSA and BET. The maximum biogas production of 179 and 206 mL/g VS have been attained when U. intestinalis has been treated with ultrasonic only and when combined microwave with Fe₃O₄ respectively, where sediment were used as inoculum in all pretreatments. From the obtained results, green Fe₃O₄ NPs enhanced the microwave (MW) treatment to produce a higher biogas yield (206 mL/g VS) when compared with individual MW (84 mL/g VS). The modified Gompertz model (R² = 0.996 was appropriate model to match the calculated biogas production and could be used more practically to distinguish the kinetics of the anaerobic digestion (AD) period. The assessment of XRD, SEM and FTIR discovered the influence of different treatment techniques on the cell wall structure of U. intestinalis. Full article

(This article belongs to the Special Issue Advanced Materials in Environmental Chemistry)

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15 pages, 16491 KiB

Open AccessArticle

Specificity and Origin of the Stability of the Sr Isotopic Ratio in Champagne Wines

by Robin Cellier, Sylvain Bérail, Julien Barre, Ekaterina Epova, Anne-Laure Ronzani, Cornelis Van Leeuwen, Stanislas Milcent, Patrick Ors and Olivier F. X. Donard

Molecules 2021, 26(16), 5104; https://doi.org/10.3390/molecules26165104 - 23 Aug 2021

Cited by 8 | Viewed by 2555

Abstract

The ⁸⁷Sr/⁸⁶Sr ratio of 39 Champagnes from six different brands, originating from the whole “Appellation d’Origine Contrôlée” (AOC) Champagne was analyzed to establish a possible relation with the geographical origin. Musts (i.e., grape juice) and base wines were also analyzed [...] Read more.

The ⁸⁷Sr/⁸⁶Sr ratio of 39 Champagnes from six different brands, originating from the whole “Appellation d’Origine Contrôlée” (AOC) Champagne was analyzed to establish a possible relation with the geographical origin. Musts (i.e., grape juice) and base wines were also analyzed to study the evolution of the Sr isotopic ratio during the elaboration process of sparkling wine. The results demonstrate that there is a very homogeneous Sr isotopic ratio (⁸⁷Sr/⁸⁶Sr = 0.70812, n = 37) and a narrow span of variability (2σ = 0.00007, n = 37). Moreover, the Sr concentrations in Champagnes have also low variability, which can be in part explained by the homogeneity of the bedrock in the AOC Champagne. Measurements of the ⁸⁷Sr/⁸⁶Sr ratio from musts and base wines show that blending during Champagne production plays a major role in the limited variability observed. Further, the ⁸⁷Sr/⁸⁶Sr of the musts were closely linked to the ⁸⁷Sr/⁸⁶Sr ratio of the vineyard soil. It appears that the ⁸⁷Sr/⁸⁶Sr of the product does not change during the elaboration process, but its variability decreases throughout the process due to blending. Both the homogeneity of the soil composition in the Champagne AOC and the blending process during the wine making process with several blending steps at different stages account for the unique and stable Sr isotopic signature of the Champagne wines. Full article

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19 pages, 6097 KiB

Open AccessArticle

Cancer Cell Membrane-Coated Nanosuspensions for Enhanced Chemotherapeutic Treatment of Glioma

by Yueyue Fan, Wenyan Hao, Yuexin Cui, Mengyu Chen, Xiaoyang Chu, Yang Yang, Yuli Wang and Chunsheng Gao

Molecules 2021, 26(16), 5103; https://doi.org/10.3390/molecules26165103 - 23 Aug 2021

Cited by 28 | Viewed by 3898

Abstract

Effective intracerebral delivery is key for glioma treatment. However, the drug delivery system within the brain is largely limited by its own adverse physical and chemical properties, low targeting efficiency, the blood–brain barrier and the blood–brain tumor barrier. Herein, we developed a simple, [...] Read more.

Effective intracerebral delivery is key for glioma treatment. However, the drug delivery system within the brain is largely limited by its own adverse physical and chemical properties, low targeting efficiency, the blood–brain barrier and the blood–brain tumor barrier. Herein, we developed a simple, safe and efficient biomimetic nanosuspension. The C6 cell membrane (CCM) was utilized to camouflaged the 10-hydroxycamptothecin nanosuspension (HCPT-NS) in order to obtain HCPT-NS/CCM. Through the use of immune escape and homotypic binding of the cancer cell membrane, HCPT-NS/CCM was able to penetrate the blood–brain barrier and target tumors. The HCPT-NS is only comprised of drugs, as well as a small amount of stabilizers that are characterized by a simple preparation method and high drug loading. Similarly, the HCPT-NS/CCM is able to achieve targeted treatment of glioma without any ligand modification, which leads it to be stable and efficient. Cellular uptake and in vivo imaging experiments demonstrated that HCPT-NS/CCM is able to effectively cross the blood–brain barrier and was concentrated at the glioma site due to the natural homing pathway. Our results reveal that the glioma cancer cell membrane is able to promote drug transport into the brain and enter the tumor via a homologous targeting mechanism. Full article

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Initially, the HCPT nanosuspensions are prepared using an alkali dissolution, and acid precipitation combined with high-pressure homogenization. Secondly, the cancer cell membrane is separated from the plasma membrane of source cells through the use of hypotonic and differential centrifugation. Then, cancer cell membranes are combined with nanosuspensions, and the mixture is fused in order to construct a biomimetic nanosuspension. Lastly, mice with in situ glioma are treated with an intravenous injection. The biomimetic nanosuspensions penetrated the blood-brain barrier, and the drug was delivered for the treatment of the tumor. Full article ">Figure 2
Characterization of HCPT-NS and HCPT-NS/CCM. Transmission electron microscopy images of HCPT-NS (A), CCMs (B) and HCPT-NS/CCM (C). The particle size of HCPT-NS and HCPT-NS/CCM. (D) The Zeta potential of HCPT-NS and HCPT-NS/CCM (E) The membrane protein of the biomimetic nanosuspensions was assessed by running the protein on an SDS-PAGE gel (F) Densitometry analysis of the Western blot (WB) and the relative gray value of membrane-specific proteins CD47 and CD44, n = 3 (G) Detection of the membrane protein concentration of Biomimetic Nanosuspension via the BCA Method. n = 3. (H). CD spectra of CCM and HCPT-NS/CCM (I). Stability of HCPT-NS and HCPT-NS/CCM in 4 °C. n = 3 (J) Release kinetics of HCPT under mimicked physiological conditions from HCPT-NS and HCPTNS/CCM at 37 °C in pH 7.4 (K), pH 6.8 (L) and FBS release medium (M), n = 3. (The data points represent the mean ± SD, ** indicates p < 0.01). Full article ">Figure 3
Cellular uptake measured through the CLSM and FCM assays. The confocal images (A,D,G) and the corresponding flow cytometry analysis (B,E,H) of bEnd.3, HUVECs, and C6 cells after exposure to free DiI and DiI-HCPTNS/CCM for 0.5 h at 37 °C at DiI concentration of 10 μg·mL −1, respectively. n = 3. Bars represent 20 μm. Image J was utilized to quantify the cellular uptake of free DiI and HCPT-NS/CCM in bEnd.3 (C), HUVECs (F) and C6 cells (I). (The data points represent the mean ± SD. ** indicates p < 0.01). Full article ">Figure 4
Schematic of the imaging of transwell model (A). Transcytosis efficiency of various formulations in the in vitro BBB model (B,D) and BBTB model (C,E) measured through the use of CLSM and Plate reader, n = 3. Antitumor effect of different HCPT preparations in C6 cells via the CCK8 assay. n = 3 (F). Antitumor effects of various HCPT preparations crossing the BBB (G) and BBTB (H) via the CCK8 assay, n = 6. (Bars represent 20 μm, red: DiI, blue: nuclei; The data points represent the mean ± SD. ** indicates p < 0.01). Full article ">Figure 5
In vivo targeting evaluation. In vivo real-time imaging of saline, DiR-HCPT-NS, and DiR-HCPT-NS/CCM in glioma-bearing mice, n = 3 (A). Ex vivo fluorescence images of the brain and other major organs of mice treated intravenously with different DiR-encapsulated nanosuspensions (B). The brain CT tumor localization scan, which indicates that biomimetic nanosuspensions are able to effectively transport drugs to the brain tissue (C). Analysis of the permeability experiment of free DiI and HCPT-NS/CCM on brain tumor site of glioma mice (D). Image J was utilized to quantify the distribution of free DiI and HCPT-NS/CCM in brain of mice that bore intracranial C6 glioma (E). (DiI: red, DAPI: blue, by 40× object lens; The data points represent the mean ± SD. ** indicates p < 0.01). Full article ">Figure 6
In vivo anti-tumor efficacy on C6 glioma-bearing mice. H&E staining of tumor tissues (A). Immunohistochemical staining of Caspase3 (B) and CD31 in tumor tissues (C). MRI of normal and glioma brains post-treatment (D). TUNEL fluorescence detection of brain tumor tissue sections (E). Kaplan–Meier survival curves of glioma-bearing mice treated with various HCPT preparations. Dosage: HCPT:8 mg·kg−1: The data points represent the mean ± SD (n = 10), ** indicates p < 0.01 (F). (DAPI: blue, FITC: green, Caspase3 and CD31: brown; 20× magnification). Full article ">Figure 7
Preliminary safety evaluation. Histopathology of major organs post-treatment. There were no major pathological changes (A). Serum biochemical indicators of mice after administration, including counts of immune system cells including WBC, Neu, Lym, and Mon (B). Counts of blood cells, including RBC and PLT (C). Liver and kidney function markers, including AST, ALT(D), Cr (E), and UA (F). The data points represent the mean ± SD (n = 3). ** indicates p < 0.01; 20× magnification. Full article ">

20 pages, 2187 KiB

Open AccessReview

Protein Adducts and Protein Oxidation as Molecular Mechanisms of Flavonoid Bioactivity

by P. Matthew Joyner

Molecules 2021, 26(16), 5102; https://doi.org/10.3390/molecules26165102 - 23 Aug 2021

Cited by 33 | Viewed by 4943

Abstract

There are tens of thousands of scientific papers about flavonoids and their impacts on human health. However, despite the vast amount of energy that has been put toward studying these compounds, a unified molecular mechanism that explains their bioactivity remains elusive. One contributing [...] Read more.

There are tens of thousands of scientific papers about flavonoids and their impacts on human health. However, despite the vast amount of energy that has been put toward studying these compounds, a unified molecular mechanism that explains their bioactivity remains elusive. One contributing factor to the absence of a general mechanistic explanation of their bioactivity is the complexity of flavonoid chemistry in aqueous solutions at neutral pH. Flavonoids have acidic protons, are redox active, and frequently auto-oxidize to produce an array of degradation products including electrophilic quinones. Flavonoids are also known to interact with specificity and high affinity with a variety of proteins, and there is evidence that some of these interactions may be covalent. This review summarizes the mechanisms of flavonoid oxidation in aqueous solutions at neutral pH and proposes the formation of protein-flavonoid adducts or flavonoid-induced protein oxidation as putative mechanisms of flavonoid bioactivity in cells. Nucleophilic residues in proteins may be able to form covalent bonds with flavonoid quinones; alternatively, specific amino acid residues such as cysteine, methionine, or tyrosine in proteins could be oxidized by flavonoids. In either case, these protein-flavonoid interactions would likely occur at specific binding sites and the formation of these types of products could effectively explain how flavonoids modify proteins in cells to induce downstream biochemical and cellular changes. Full article

(This article belongs to the Special Issue Biosynthesis and Biological Activities of Flavonoids)

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A summary of the most reasonable primary routes of flavonoid bioactivity in humans. Flavonoids will exhibit most of their bioactivity in intestinal epithelial cells and in gut microbial cells. After metabolic degradation by intestinal microflora, microbial metabolites of flavonoids are absorbed by the intestines and excreted. Full article ">Figure 2
The core flavonoid scaffold for flavones and flavan along with the structures of the representative flavone quercetin and the flavan-3-ol EGCG. Full article ">Figure 3
A proposed general auto-oxidative mechanism for flavonoids using quercetin as a representative structure. Full article ">Figure 4
Glutathione forms flavonoid adducts via Michael addition to the quinone methide isomers of oxidized quercetin. Full article ">Figure 5
Interactions between flavonoid ligands and proteins from X-ray crystal structures; residues that could either form adducts or be oxidized by flavonoids are labeled. (A) the tyrosine kinase Hck (green) with quercetin (gray) (PDB 2HCK). The distance from K295 to the catechol group of quercetin is within a reasonable distance for electron transfer; (B) human inositol polyphosphate multikinase (IMPK; cyan) with quercetin (gray) (PDB 6M89); (C) prostaglandin F synthase (magenta) with NADPH (cyan) and the quercetin-3-O-glycoside rutin (gray). In all three images, water molecules are shown as red asterisks. Full article ">Figure 6
Comparison of structures of quercetin and eriodictyol and their inhibitory activity against human inositol polyphosphate multikinase (IPMK). IC50 values from [<a href="#B108-molecules-26-05102" class="html-bibr">108</a>]. Full article ">Figure 7
Proposed reaction scheme of nucleophilic protein residues with electrophilic flavonoid quinones. Expected characteristic mass shifts are shown for the quercetin quinone (top) and reduced quercetin (bottom). Full article ">

12 pages, 1282 KiB

Open AccessArticle

Guiding Molecularly Imprinted Polymer Design by Pharmacophore Modeling

by Wiebke Derz, Melita Fleischmann and Paul W. Elsinghorst

Molecules 2021, 26(16), 5101; https://doi.org/10.3390/molecules26165101 - 23 Aug 2021

Cited by 3 | Viewed by 2808

Abstract

Molecularly imprinted polymers (MIP) combine the selectivity of immunoaffinity chromatography with the robustness of common solid-phase extraction in what is referred to as molecularly imprinted solid-phase extraction (MISPE). This contribution shows how MIP design may be guided by pharmacophore modeling for the example [...] Read more.

Molecularly imprinted polymers (MIP) combine the selectivity of immunoaffinity chromatography with the robustness of common solid-phase extraction in what is referred to as molecularly imprinted solid-phase extraction (MISPE). This contribution shows how MIP design may be guided by pharmacophore modeling for the example of citrinin, which is an emerging mycotoxin from cereals. The obtained pharmacophore model allowed searching public databases for a set of citrinin-mimicking molecular surrogates. Imprinted and non-imprinted polymers were subsequently obtained through bulk and core-shell polymerization in the presence of these surrogates. Evaluation of their binding ability for citrinin and structurally related ochratoxin A revealed a promising MIP derived from rhodizonic acid. A protocol for MISPE of citrinin from cereals was subsequently developed and compared to immunoaffinity chromatography with respect to clean-up efficiency and recovery. Full article

(This article belongs to the Special Issue Method Development of Sampling Preparation Techniques)

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Schematic illustration of MIP synthesis by bulk polymerization. First, a template, functional monomers, cross-linker, and radical starter (AIBN) are dissolved in porogen followed by heat-induced polymerization (a). The resulting polymer block is crushed, milled, and sieved to obtain uniformly sized particles, which are washed thoroughly to remove the template (b). Full article ">Figure 2
Schematic illustration of core-shell MIP synthesis. Core particles are obtained through heat-induced polymerization of functional monomers using a cross-linker (a), this step can be repeated to increase core size. Then, core particles are mixed with the template and functional monomers for MIP-shell formation (b), which is released by thorough washing (c). Full article ">Figure 3
Molecular structures (a), results of MMFF94 energy minimization (b), and pharmacophore models (c) of CIT (1) and the surrogate template rhodizonic acid (RHO, 2). Hydrophobic areas are marked yellow, hydrophilic ones are marked red. Areas enabling hydrogen bonding are marked green, while blue regions denote potential ionic interactions. Full article ">Figure 4
Chromatograms of CIT (1, 400 ng/mL) and OTA (2, 30 ng/mL) of oats spiked before (—) and after (---) MISPE (see Materials and Methods for details). Full article ">

15 pages, 1375 KiB

Open AccessFeature PaperArticle

Donkey Milk Fermentation by Lactococcus lactis subsp. cremoris and Lactobacillus rhamnosus Affects the Antiviral and Antibacterial Milk Properties

by Simona Cirrincione, Anna Luganini, Cristina Lamberti, Marcello Manfredi, Laura Cavallarin, Maria Gabriella Giuffrida and Enrica Pessione

Molecules 2021, 26(16), 5100; https://doi.org/10.3390/molecules26165100 - 23 Aug 2021

Cited by 12 | Viewed by 2988

Abstract

Background: Milk is considered an important source of bioactive peptides, which can be produced by endogenous or starter bacteria, such as lactic acid bacteria, that are considered effective and safe producers of food-grade bioactive peptides. Among the various types of milk, donkey milk [...] Read more.

Background: Milk is considered an important source of bioactive peptides, which can be produced by endogenous or starter bacteria, such as lactic acid bacteria, that are considered effective and safe producers of food-grade bioactive peptides. Among the various types of milk, donkey milk has been gaining more and more attention for its nutraceutical properties. Methods: Lactobacillus rhamnosus 17D10 and Lactococcus lactis subsp. cremoris 40FEL3 were selected for their ability to produce peptides from donkey milk. The endogenous peptides and those obtained after bacterial fermentation were assayed for their antioxidant, antibacterial, and antiviral activities. The peptide mixtures were characterized by means of LC-MS/MS and then analyzed in silico using the Milk Bioactive Peptide DataBase. Results: The peptides produced by the two selected bacteria enhanced the antioxidant activity and reduced E. coli growth. Only the peptides produced by L. rhamnosus 17D10 were able to reduce S. aureus growth. All the peptide mixtures were able to inhibit the replication of HSV-1 by more than 50%. Seventeen peptides were found to have 60% sequence similarity with already known bioactive peptides. Conclusions: A lactic acid bacterium fermentation process is able to enhance the value of donkey milk through bioactivities that are important for human health. Full article

(This article belongs to the Special Issue Study of Bioactive Proteins and Peptides from Microbial and Food Origin)

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Antioxidant activity of the peptides from donkey milk inoculated with L. rhamnosus 17D10 (LrP), L. lactis subsp. cremoris 40FEL3 (LcP), and not inoculated (CtlP). The antioxidant activity is expressed as the half-maximal inhibitory concentration (IC50). Full article ">Figure 2
Antibacterial activity of the peptides from donkey milk inoculated with L. rhamnosus 17D10 (LrP), L. lactis subsp. cremoris 40FEL3 (LcP), and not inoculated (CtlP). The antibacterial activity was evaluated against E. coli and S. aureus clinical isolates as means of pathogen growth inhibition. (a) Antimicrobial activity of LcP and CtlP samples vs. E. coli; (b) the three biological replicates of LrP samples vs. E. coli were reported individually due to their high variability; (c) antimicrobial activity of LrP, LcP, and CtlP samples vs. S. aureus. Full article ">Figure 3
Antiviral activity of the peptides from donkey milk inoculated with L. rhamnosus 17D10 (LrP), L. lactis subsp. cremoris 40FEL3 (LcP), and not inoculated (CtlP). The antiviral activity was evaluated against an HSV-1 clinical isolate. As positive control, the infected cells were treated with acyclovir (ACV, 2 µM) or treated with DMSO as negative control (CV). The results presented in all panels were analyzed with Bonferroni post-test correction for multiple comparisons. *** p < 0.001, and **** p < 0.0001 versus calibrator sample (CV). Full article ">Figure 4
Venn diagrams showing the distribution of the identified peptides in the three biological replicates of each condition: (a) LrP, (b) LcP, (c) CtlP, and (d) comparing the three different tested conditions. Full article ">Figure 5
Histogram showing the main milk proteins from which the peptides from donkey milk inoculated with L. rhamnosus 17D10 (LrP), L. lactis subsp. cremoris 40FEL3 (LcP), and not inoculated (CtlP) were decrypted. Full article ">

12 pages, 1689 KiB

Open AccessArticle

Development of Highly Sensitive Raman Spectroscopy for Subnano and Single-Atom Detection

by Yuansen Tang, Naoki Haruta, Akiyoshi Kuzume and Kimihisa Yamamoto

Molecules 2021, 26(16), 5099; https://doi.org/10.3390/molecules26165099 - 23 Aug 2021

Cited by 6 | Viewed by 3403

Abstract

Direct detection and characterisation of small materials are fundamental challenges in analytical chemistry. A particle composed of dozens of metallic atoms, a so-called subnano-particle (SNP), and a single-atom catalyst (SAC) are ultimate analysis targets in terms of size, and the topic is now [...] Read more.

Direct detection and characterisation of small materials are fundamental challenges in analytical chemistry. A particle composed of dozens of metallic atoms, a so-called subnano-particle (SNP), and a single-atom catalyst (SAC) are ultimate analysis targets in terms of size, and the topic is now attracting increasing attention as innovative frontier materials in catalysis science. However, characterisation techniques for the SNP and SAC adsorbed on substrates requires sophisticated and large-scale analytical facilities. Here we demonstrate the development of an ultrasensitive, laboratory-scale, vibrational spectroscopic technique to characterise SNPs and SACs. The fine design of nano-spatial local enhancement fields generated by the introduction of anisotropic stellate-shaped signal amplifiers expands the accessibility of small targets on substrates into evanescent electromagnetic fields, achieving not only the detection of isolated small targets but also revealing the effects of intermolecular/interatomic interactions within the subnano configuration under actual experimental conditions. Such a development of “in situ subnano spectroscopy” will facilitate a comprehensive understanding of subnano and SAC science. Full article

(This article belongs to the Special Issue Coordination Programming for Electro-, Magneto-, and Photofunctional Molecular Systems: A Theme Issue in Honor of Prof. Dr. Hiroshi Nishihara)

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Enhanced Raman spectroscopy for the detection of subnano-particles. Schematics of (a) surface-enhanced Raman spectroscopy at a roughened metallic surface, (b) optimised shell-isolated nanoparticle enhanced Raman spectroscopy using 120 nm diameter Au nanoparticles as optical amplifiers, (c) enhanced Raman spectroscopy with shell-isolated nanostars which produce an abundant proportion of hotspots at the surface that allow detection of single molecules and small particles. Full article ">Figure 2
Characterisation of PVP-protected Au nanostars. SEM images of PVP-protected Au nanostars synthesised by different amounts of the seed solution (Vseed). (a) Vseed = 40 and (b) 140 μL, respectively (scale bar: 50 nm). (c) The particle size, acquired based on the measurement of the longest length from the tip apex to the opposite core surface, was plotted as a function of Vseed, where the error bar shows the standard deviation of the size distribution. (d) A series of UV-Vis spectra of Au nanostars synthesised with different Vseed, and (e) SPR peak positions (λSPR) as a function of Vseed. (f) A series of Raman spectra for a dendrimer sample with shell-isolated Au nanostars with different Vseed and (g) the corresponding signal intensity at 1580 cm−1 as a function of Vseed, normalised with that from the blank spectrum acquired in the absence of the Au nanostar. Full article ">Figure 3
Enhancement effect of shell-isolated Au nano-structured amplifiers. (a) Raman spectra of mercaptobenzoic acid self-assembled monolayer (MBA-SAM) on Au(111) enhanced by (i) 55 nm Au nano-spheres, (ii) 120 nm Au nano-spheres and (iii) 28 nm Au nanostars. The excitation wavelength was 632.8 nm. (b) Comparison of Raman signal intensities of MBA-SAM on Au(111) with different optical amplifiers calculated for the peak intensity at 1583 cm−1 which was assigned to the ring breathing mode. Full article ">Figure 4
Raman studies for the Py molecules on the Pt subnano-islands and Pt single-atoms with shell-isolated Au nanostars. (a–c) TEM images of Pt subnano-islands prepared by APD (scale bar: 5 nm), (d–f) schematic images and (g–i) SHINER spectra of Py molecules adsorbed on the Pt islands and atoms. Pt subnano-islands were prepared by (a,d,g) 100, (b,e,h) 10 and (c,f,i) 1 APD pulses, respectively. The former two samples had the average sizes of (a) 2.0 ± 0.4 and (b) 0.8 ± 0.2 nm, respectively, while the latter sample gave individually deposited atoms on the HOPG surface. Full article ">Figure 5
In situ Raman study of CO adsorbed on Pt islands with shell-isolated Au nanostars: (a) schematics of in situ shell-isolated nanostar enhanced Raman spectroscopy and the homemade cell. (b) Electrode potential-dependent steady-state SHINER spectra for CO adsorbed on Pt islands (0.9 nm in diameter) in CO-saturated 0.1 M HClO4, and (c) potential dependent Raman peak frequency shifts of the CO stretching mode. The Stark tuning rate was 87 cm−1/V. Full article ">

13 pages, 15664 KiB

Open AccessArticle

Fluorescent Azasteroids through Ultrasound Assisted Cycloaddition Reactions

by Costel Moldoveanu, Ionel Mangalagiu and Gheorghita Zbancioc

Molecules 2021, 26(16), 5098; https://doi.org/10.3390/molecules26165098 - 23 Aug 2021

Cited by 6 | Viewed by 1992

Abstract

We report here the synthesis and optical spectral properties of several new azasteroid derivatives. The formation of these compounds was explained based on the most probable mechanism. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between benzo[f]quinoline and methylpropiolate or dimethyl acetylenedicarboxylate [...] Read more.

We report here the synthesis and optical spectral properties of several new azasteroid derivatives. The formation of these compounds was explained based on the most probable mechanism. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between benzo[f]quinoline and methylpropiolate or dimethyl acetylenedicarboxylate (DMAD). A selective and efficient way for [3+2]-dipolar cycloaddition of benzo[f]quinolinium ylides under ultrasound (US) irradiation (20 kHz processing frequency) is presented. We report substantially higher yields under US irradiation, whereas the solvent amounts required are at least three-fold less compared to classical heating. The azasteroid derivatives are blue emitters with λ_max of fluorescence around 430–450 nm. A certain influence of the azasteroid substituents concerning absorption and fluorescent properties was observed. Compounds anchored with a bulky pivaloyl group or without a C=O carbonyl group have shown increased fluorescence intensity. Full article

(This article belongs to the Special Issue Advances in Ultrasound Chemistry)

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The absorption spectra recorded in trichloromethane solution of the azasteroid derivatives: (I)-5a–c; (II)-7a–c, and 8c. Full article ">Figure 2
The absorption spectra recorded in cyclohexane solution of the azasteroid derivatives: (I)-5a–c; (II)-7a–c and 8c. Full article ">Figure 3
The absorption (black line) and emission (blue line) spectra of azasteroid derivatives 5c, 7c, and 8c in trichloromethane (left column) and cyclohexane (right column). The excitation wavelength was: 380 nm for sample 5c and 365 nm for samples 7c and 8c. Full article ">Figure 4
The emission spectra recorded in trichloromethane solution of the azasteroid derivatives: (I)-5a–c; (II)-7a–c and 8c. Full article ">Figure 5
The emission spectra recorded in cyclohexane solution of the azasteroid derivatives: (I)-5a–c; (II)-7a–c and 8c. Full article ">Scheme 1
Reaction pathway to generate azasteroid derivatives. Full article ">Scheme 2
The most probable mechanism of the cycloaddition reaction. Full article ">

25 pages, 1475 KiB

Open AccessArticle

Fungal α-1,3-Glucan as a New Pathogen-Associated Molecular Pattern in the Insect Model Host Galleria mellonella

by Sylwia Stączek, Agnieszka Zdybicka-Barabas, Iwona Wojda, Adrian Wiater, Paweł Mak, Piotr Suder, Krzysztof Skrzypiec and Małgorzata Cytryńska

Molecules 2021, 26(16), 5097; https://doi.org/10.3390/molecules26165097 - 23 Aug 2021

Cited by 11 | Viewed by 2933

Abstract

Recognition of pathogen-associated molecular patterns (PAMPs) by appropriate pattern recognition receptors (PRRs) is a key step in activating the host immune response. The role of a fungal PAMP is attributed to β-1,3-glucan. The role of α-1,3-glucan, another fungal cell wall polysaccharide, in modulating [...] Read more.

Recognition of pathogen-associated molecular patterns (PAMPs) by appropriate pattern recognition receptors (PRRs) is a key step in activating the host immune response. The role of a fungal PAMP is attributed to β-1,3-glucan. The role of α-1,3-glucan, another fungal cell wall polysaccharide, in modulating the host immune response is not clear. This work investigates the potential of α-1,3-glucan as a fungal PAMP by analyzing the humoral immune response of the greater wax moth Galleria mellonella to Aspergillus niger α-1,3-glucan. We demonstrated that 57-kDa and 61-kDa hemolymph proteins, identified as β-1,3-glucan recognition proteins, bound to A. niger α-1,3-glucan. Other hemolymph proteins, i.e., apolipophorin I, apolipophorin II, prophenoloxidase, phenoloxidase activating factor, arylphorin, and serine protease, were also identified among α-1,3-glucan-interacting proteins. In response to α-1,3-glucan, a 4.5-fold and 3-fold increase in the gene expression of antifungal peptides galiomicin and gallerimycin was demonstrated, respectively. The significant increase in the level of five defense peptides, including galiomicin, corresponded well with the highest antifungal activity in hemolymph. Our results indicate that A. niger α-1,3-glucan is recognized by the insect immune system, and immune response is triggered by this cell wall component. Thus, the role of a fungal PAMP for α-1,3-glucan can be postulated. Full article

(This article belongs to the Special Issue Fungal Biopolymer Discovery, Characterization and Development)

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11 pages, 2045 KiB

Open AccessFeature PaperArticle

Integratomics of Human Dermal Fibroblasts Treated with Low Molecular Weight Hyaluronic Acid

by Silvia Radrezza, Gilda Aiello, Giovanna Baron, Giancarlo Aldini, Marina Carini and Alfonsina D’Amato

Molecules 2021, 26(16), 5096; https://doi.org/10.3390/molecules26165096 - 23 Aug 2021

Cited by 2 | Viewed by 3256

Abstract

Hyaluronic acid (HA) is a glycosaminoglycan very common in commercial products from pharmaceuticals to cosmetics due to its widespread distribution in humans and its diversified physico-chemical proprieties. Despite its extended use and preliminary evidence showing even also opposite activities to the native form, [...] Read more.

Hyaluronic acid (HA) is a glycosaminoglycan very common in commercial products from pharmaceuticals to cosmetics due to its widespread distribution in humans and its diversified physico-chemical proprieties. Despite its extended use and preliminary evidence showing even also opposite activities to the native form, the precise cellular effects of HA at low-molecular-weight (LWM-HA) are currently unclear. The ‘omics sciences currently in development offer a new and combined perspective on the cellular and organismal environment. This work aims to integrate lipidomics analyses to our previous quantitative proteomics one for a multi-omics vision of intra- and extra-cellular impact of different concentrations (0.125, 0.25, and 0.50%) of LMW-HA (20–50 kDa) on normal human dermal fibroblasts by LC-high resolution mass spectrometry (LC-HRMS). Untargeted lipidomics allowed us to identify 903 unique lipids mostly represented by triacylglycerols, ceramides, and phosphatidylcholines. According to proteomics analyses, LMW-HA 0.50% was the most effective concentration also in the lipidome rearrangement especially stimulating the synthesis of ceramides involved in skin hydration and reparation, cell signaling, and energy balance. Finally, integrative analyses showed 25 nodes covering several intra- and extra-cellular functions. The more complete comprehension of intra- and extra-cellular effects of LMW-HA here pointed out will be useful to further exploit its features and improve current formulations even though further studies on lipids biosynthesis and degradation are necessary. Full article

(This article belongs to the Special Issue Nutricosmetics: A New Area of Cosmetic Product)

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15 pages, 3593 KiB

Open AccessArticle

Efficient Use of Carbon Fibers as Heating Elements for Curing of Epoxy Matrix Composites

by Lykourgos C. Kontaxis, Ioannis E. Chontzoglou and George C. Papanicolaou

Molecules 2021, 26(16), 5095; https://doi.org/10.3390/molecules26165095 - 23 Aug 2021

Cited by 3 | Viewed by 3096

Abstract

The aim of this study is to achieve a fully cured thermoset matrix that is heated by a direct electric current passing through the reinforcement fibers i.e., the Joule heating effect. Two types of fibers were used as heating elements for curing the [...] Read more.

The aim of this study is to achieve a fully cured thermoset matrix that is heated by a direct electric current passing through the reinforcement fibers i.e., the Joule heating effect. Two types of fibers were used as heating elements for curing the epoxy resins. Kanthal resistance fibers were used as reference heating elements and subsequently, they were replaced by a Torayca Carbon Tow of the same radius. The specimens were cured by the heat produced by a direct electric current passing through the fibers and achieving temperatures of 50 °C and 70 °C. Specimens cured in a conventional oven were also manufactured, to compare the resistance heating method to the conventional one. Next, all specimens were mechanically characterized in a quasi-static three-point bending mode of loading and experimental results were compared to derive useful conclusions concerning the applicability of the technique to polymer/composite materials mass production. Finally, a preliminary economical study concerning power consumption needed for the application of both the traditional oven curing and the carbon fibers heating elements use for the manufacturing of the same amounts of materials is presented, showing a maximum financial benefit that can be achieved, on the order of 68%. Full article

(This article belongs to the Special Issue Metallic and Composite Materials and Structures)

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23 pages, 1604 KiB

Open AccessArticle

Acanthaster planci Inhibits PCSK9 and Lowers Cholesterol Levels in Rats

by Nurjannatul Naim Kamaruddin, Nor Azwin Hajri, Yosie Andriani, Aina Farahiyah Abdul Manan, Tengku Sifzizul Tengku Muhammad and Habsah Mohamad

Molecules 2021, 26(16), 5094; https://doi.org/10.3390/molecules26165094 - 23 Aug 2021

Cited by 5 | Viewed by 3637

Abstract

Atherosclerosis is the main cause of cardiovascular diseases which in turn, lead to the highest number of mortalities globally. This pathophysiological condition is developed due to a constant elevated level of plasma cholesterols. Statin is currently the widely used treatment in reducing the [...] Read more.

Atherosclerosis is the main cause of cardiovascular diseases which in turn, lead to the highest number of mortalities globally. This pathophysiological condition is developed due to a constant elevated level of plasma cholesterols. Statin is currently the widely used treatment in reducing the level of cholesterols, however, it may cause adverse side effects. Therefore, there is an urgent need to search for new alternative treatment. PCSK9 is an enzyme responsible in directing LDL-receptor (LDL-R)/LDL-cholesterols (LDL-C) complex to lysosomal degradation, preventing the receptor from recycling back to the surface of liver cells. Therefore, PCSK9 offers a potential target to search for small molecule inhibitors which inhibit the function of this enzyme. In this study, a marine invertebrate Acanthaster planci, was used to investigate its potential in inhibiting PCSK9 and lowering the levels of cholesterols. Cytotoxicity activity of A. planci on human liver HepG2 cells was carried out using the MTS assay. It was found that methanolic extract and fractions did not exhibit cytotoxicity effect on HepG2 cell line with IC₅₀ values of more than 30 µg/mL. A compound deoxythymidine also did not exert any cytotoxicity activity with IC₅₀ value of more than 4 µg/mL. Transient transfection and luciferase assay were conducted to determine the effects of A. planci on the transcriptional activity of PCSK9 promoter. Methanolic extract and Fraction 2 (EF2) produced the lowest reduction in PCSK9 promoter activity to 70 and 20% of control at 12.5 and 6.25 μg/mL, respectively. In addition, deoxythymidine also decreased PCSK9 promoter activity to the lowest level of 60% control at 3.13 μM. An in vivo study using Sprague Dawley rats demonstrated that 50 and 100 mg/kg of A. planci methanolic extract reduced the total cholesterols and LDL-C levels to almost similar levels of untreated controls. The level of serum glutamate oxalate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) showed that the administration of the extract did not produce any toxicity effect and cause any damage to rat liver. The results strongly indicate that A. planci produced a significant inhibitory activity on PCSK9 gene expression in HepG2 cells which may be responsible for inducing the uptake of cholesterols by liver, thus, reducing the circulating levels of total cholesterols and LDL-C. Interestingly, A. planci also did show any adverse hepato-cytotoxicity and toxic effects on liver. Thus, this study strongly suggests that A. planci has a vast potential to be further developed as a new class of therapeutic agent in lowering the blood cholesterols and reducing the progression of atherosclerosis. Full article

(This article belongs to the Special Issue Bioactive Compounds on Health and Disease)

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13 pages, 1076 KiB

Open AccessArticle

Fabrication of Membrane Sensitive Electrodes for the Validated Electrochemical Quantification of Anti-Osteoporotic Drug Residues in Pharmaceutical Industrial Wastewater

by Sherif A. Abdel-Gawad, Obaid Afzal, Hany H. Arab, Alhumaidi B. Alabbas and Abdulmalik M. Alqarni

Molecules 2021, 26(16), 5093; https://doi.org/10.3390/molecules26165093 - 22 Aug 2021

Cited by 2 | Viewed by 2299

Abstract

Accurate and precise application of ion-selective electrodes (ISEs) in the quantification of environmental pollutants is a strenuous task. In this work, the electrochemical response of alendronate sodium trihydrate (ALN) was evaluated by the fabrication of two sensitive and delicate membrane electrodes, viz. polyvinyl [...] Read more.

Accurate and precise application of ion-selective electrodes (ISEs) in the quantification of environmental pollutants is a strenuous task. In this work, the electrochemical response of alendronate sodium trihydrate (ALN) was evaluated by the fabrication of two sensitive and delicate membrane electrodes, viz. polyvinyl chloride (PVC) and glassy carbon (GC) electrodes. A linear response was obtained at concentrations from 1 × 10⁻⁵ to 1 × 10⁻² M for both electrodes. A Nernstian slope of 29 mV/decade over a pH range of 8–11 for the PVC and GC membrane electrodes was obtained. All assay settings were carefully adjusted to obtain the best electrochemical response. The proposed technique was effectively applied for the quantification of ALN in pure form and wastewater samples, acquired from manufacturing industries. The proposed electrodes were effectively used for the determination of ALN in real wastewater samples without any prior treatment. The current findings guarantee the applicability of the fabricated ISEs for the environmental monitoring of ALN. Full article

(This article belongs to the Special Issue 25th Anniversary of Molecules—Invited Papers in the Electrochemistry Section)

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15 pages, 4002 KiB

Open AccessArticle

Interaction between Curcumin and β-Casein: Multi-Spectroscopic and Molecular Dynamics Simulation Methods

by Ruichen Zhao, Xiaoli Qin and Jinfeng Zhong

Molecules 2021, 26(16), 5092; https://doi.org/10.3390/molecules26165092 - 22 Aug 2021

Cited by 18 | Viewed by 4261

Abstract

Effect of temperature and pH on the interaction of curcumin with β-casein was explored by fluorescence spectroscopy, ultraviolet-visible spectroscopy and molecular dynamics simulation. The spectroscopic results showed that curcumin could bind to β-casein to form a complex which was driven mainly by electrostatic [...] Read more.

Effect of temperature and pH on the interaction of curcumin with β-casein was explored by fluorescence spectroscopy, ultraviolet-visible spectroscopy and molecular dynamics simulation. The spectroscopic results showed that curcumin could bind to β-casein to form a complex which was driven mainly by electrostatic interaction. The intrinsic fluorescence of β-casein was quenched by curcumin through static quenching mechanism. The binding constants of curcumin to β-casein were 6.48 × 10⁴ L/mol (298 K), 6.17 × 10⁴ L/mol (305 K) and 5.73 × 10⁴ L/mol (312 K) at pH 2.0, which was greater than that (3.98 × 10⁴ L/mol at 298 K, 3.90 × 10⁴ L/mol at 305 K and 3.41 × 10⁴ L/mol at 312 K) at pH 7.4. Molecular docking study showed that binding energy of β-casein-curcumin complex at pH 2.0 (−7.53 kcal/mol) was lower than that at pH 7.4 (−7.01 kcal/mol). The molecular dynamics simulation study showed that the binding energy (−131.07 kJ/mol) of β-casein-curcumin complex was relatively low at pH 2.0 and 298 K. α-Helix content in β-casein was decreased and random coil content was increased in the presence of curcumin. These results can promote a deep understanding of interaction between curcumin and β-casein and provide a reference for improving the bioavailability of curcumin. Full article

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Fluorescence spectra of casein in the absence and presence of curcumin at 298 K at pH 7.4 (A) and pH 2.0 (B). The curcumin concentrations in curves 1–6 were 0 × 10−6, 2 × 10−6, 4 × 10−6, 6 × 10−6, 8 × 10−6, and 10 × 10−6 mol/L. Curve 7 was for 0.05 mol/L Tris-HCl buffer. Casein concentration was 0.2 g/L. Full article ">Figure 2
Ultraviolet-visible spectra of casein in the absence and presence of curcumin at 298 K at pH 7.4 (A) and pH 2.0 (B). The curcumin concentrations in curves 1–6 were 0 × 10−6, 2 × 10−6, 4 × 10−6, 6 × 10−6, 8 × 10−6, and 10 × 10−6 mol/L. Casein concentration was 0.2 g/L. Full article ">Figure 2 Cont.
Ultraviolet-visible spectra of casein in the absence and presence of curcumin at 298 K at pH 7.4 (A) and pH 2.0 (B). The curcumin concentrations in curves 1–6 were 0 × 10−6, 2 × 10−6, 4 × 10−6, 6 × 10−6, 8 × 10−6, and 10 × 10−6 mol/L. Casein concentration was 0.2 g/L. Full article ">Figure 3
β-casein model (A) and its Ramachandran plot (B). Full article ">Figure 4
3D image of the best binding pose for curcumin docked into the β-casein at pH 7.4 (A) and pH 2.0 (D), 3D characterization of the interacted residues between curcumin and β-casein at pH 7.4 (B) and pH 2.0 (E), and 2D characterization of the interacted residues between curcumin and β-casein at pH 7.4 (C) and pH 2.0 (F). Full article ">Figure 5
The backbone RMSD of β-casein in the absence/presence of curcumin at pH 7.4 (A) and pH 2.0 (B). Full article ">Figure 6
The effects of temperature on the number of hydrogen bonds of β-casein-curcumin complex during 60 ns MD simulation at pH 7.4 (A) and pH 2.0 (B). Full article ">Figure 7
Gradient isosurface and scatter plot of the complex under different pH values and temperatures. Full article ">

11 pages, 5945 KiB

Open AccessReview

Significance of Oligomeric and Fibrillar Species in Amyloidosis: Insights into Pathophysiology and Treatment

by Haruki Koike, Yohei Iguchi, Kentaro Sahashi and Masahisa Katsuno

Molecules 2021, 26(16), 5091; https://doi.org/10.3390/molecules26165091 - 22 Aug 2021

Cited by 27 | Viewed by 4967

Abstract

Amyloidosis is a term referring to a group of various protein-misfolding diseases wherein normally soluble proteins form aggregates as insoluble amyloid fibrils. How, or whether, amyloid fibrils contribute to tissue damage in amyloidosis has been the topic of debate. In vitro studies have [...] Read more.

Amyloidosis is a term referring to a group of various protein-misfolding diseases wherein normally soluble proteins form aggregates as insoluble amyloid fibrils. How, or whether, amyloid fibrils contribute to tissue damage in amyloidosis has been the topic of debate. In vitro studies have demonstrated the appearance of small globular oligomeric species during the incubation of amyloid beta peptide (Aβ). Nerve biopsy specimens from patients with systemic amyloidosis have suggested that globular structures similar to Aβ oligomers were generated from amorphous electron-dense materials and later developed into mature amyloid fibrils. Schwann cells adjacent to amyloid fibrils become atrophic and degenerative, suggesting that the direct tissue damage induced by amyloid fibrils plays an important role in systemic amyloidosis. In contrast, there is increasing evidence that oligomers, rather than amyloid fibrils, are responsible for cell death in neurodegenerative diseases, particularly Alzheimer’s disease. Disease-modifying therapies based on the pathophysiology of amyloidosis have now become available. Aducanumab, a human monoclonal antibody against the aggregated form of Aβ, was recently approved for Alzheimer’s disease, and other monoclonal antibodies, including gantenerumab, solanezumab, and lecanemab, could also be up for approval. As many other agents for amyloidosis will be developed in the future, studies to develop sensitive clinical scales for identifying improvement and markers that can act as surrogates for clinical scales should be conducted. Full article

(This article belongs to the Special Issue Advances in Protein Folding and Misfolding, and Relations to Functions)

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Amorphous electron-dense materials and clusters of globular structures in the endoneurium. A cross section of the sural nerve biopsy specimen from a patient with hereditary transthyretin (ATTRv) amyloidosis. Numerous small globular structures with a diameter of several nanometers seem to be generated from amorphous extracellular electron-dense materials supposed to contain amyloidogenic transthyretin. A cluster of globular structures and amorphous electron-dense materials are indicated by arrowheads and asterisks, respectively. The circular structures, with diameters of around 50 nm, are collagen fibers. Uranyl acetate and lead citrate stain. Scale bar = 0.1 μm. Full article ">Figure 2
Amyloid fibrils in the endoneurium. A cross section of the sural nerve biopsy specimen from a patient with hereditary transthyretin (ATTRv) amyloidosis. The globular structures shown in <a href="#molecules-26-05091-f001" class="html-fig">Figure 1</a> seemed to develop into mature amyloid fibrils because elongated fibrillar structures are frequently found in the vicinity of such globular structures. The circular structures with diameters of around 50 nm are collagen fibers. Collagen fibers surrounded by squares seem to get involved in the aggregates of amyloid fibrils. Uranyl acetate and lead citrate stain. Scale bar = 0.1 μm. Full article ">Figure 3
Atrophy and degeneration of Schwann cells apposed by amyloid fibrils. A cross section of a sural nerve biopsy specimen from a patient with hereditary transthyretin (ATTRv) amyloidosis. Schwann cells, particularly small ones associated with small-diameter nerve fibers, become atrophic when they are adjacent to amyloid fibril aggregates. Atrophy of Schwan cells is conspicuous in the upper right, where a mass of amyloid fibrils aggregation is present. The basement and cytoplasmic membranes apposed to amyloid fibrils become indistinct (arrows), while those in the lower left part, where amyloid fibrils are not present, are preserved (arrowheads). Uranyl acetate and lead citrate stain. Scale bar = 2 μm. Full article ">

16 pages, 4699 KiB

Open AccessArticle

Effect of Precursor Nature and Sol-Gel Synthesis Conditions on TiO₂ Aerogel’s Structure

by Jolanta Doneliene, Egle Fataraite-Urboniene, Matas Rudzikas, Saulius Pakalka, Nina Danchova and Juras Ulbikas

Molecules 2021, 26(16), 5090; https://doi.org/10.3390/molecules26165090 - 22 Aug 2021

Cited by 7 | Viewed by 2939

Abstract

The aim of this investigation was to synthesize high porosity TiO₂ aerogel by applying sol-gel and subcritical drying methods and to identify the influence of reagent’s nature and synthesis conditions on their structural and optical properties. Methods of XRD, FT-IR, BET, STA, [...] Read more.

The aim of this investigation was to synthesize high porosity TiO₂ aerogel by applying sol-gel and subcritical drying methods and to identify the influence of reagent’s nature and synthesis conditions on their structural and optical properties. Methods of XRD, FT-IR, BET, STA, SEM, and UV-vis were applied to investigate and compare the properties of synthesized TiO₂ aerogels and to determine the most effective synthesis route. The structural parameters of the synthesized materials can be varied by changing the precursor type (titanium (IV), isopropoxide (TIP), or tetrabutylorthotitanate (TBOT)) and the nature of the solvent used for additional exchange (n-hexane (nH), cyclohexane (CH), or diethyl ether (DE)). All of the subcritical dried samples show the amorphous structure, which tends to crystallize into the anatase phase after calcination. The number of micro and mesopores and the specific surface area depends on the synthesis conditions. The pores with the highest diameter have been found for additionally nH exchanged and aged aerogel synthesized from precursor TIP. Despite the imperfections in the structure, the produced aerogels show structural and optical properties typical of the TiO₂ structures mentioned in the literature. Full article

(This article belongs to the Special Issue Sol-Gel Composites and Aerogels)

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15 pages, 1482 KiB

Open AccessArticle

Effects of a Peripherally Restricted Hybrid Inhibitor of CB1 Receptors and iNOS on Alcohol Drinking Behavior and Alcohol-Induced Endotoxemia

by Luis Santos-Molina, Alexa Herrerias, Charles N. Zawatsky, Ozge Gunduz-Cinar, Resat Cinar, Malliga R. Iyer, Casey M. Wood, Yuhong Lin, Bin Gao, George Kunos and Grzegorz Godlewski

Molecules 2021, 26(16), 5089; https://doi.org/10.3390/molecules26165089 - 22 Aug 2021

Cited by 6 | Viewed by 3000

Abstract

Alcohol consumption is associated with gut dysbiosis, increased intestinal permeability, endotoxemia, and a cascade that leads to persistent systemic inflammation, alcoholic liver disease, and other ailments. Craving for alcohol and its consequences depends, among other things, on the endocannabinoid system. We have analyzed [...] Read more.

Alcohol consumption is associated with gut dysbiosis, increased intestinal permeability, endotoxemia, and a cascade that leads to persistent systemic inflammation, alcoholic liver disease, and other ailments. Craving for alcohol and its consequences depends, among other things, on the endocannabinoid system. We have analyzed the relative role of central vs. peripheral cannabinoid CB1 receptors (CB1R) using a “two-bottle” as well as a “drinking in the dark” paradigm in mice. The globally acting CB1R antagonist rimonabant and the non-brain penetrant CB1R antagonist JD5037 inhibited voluntary alcohol intake upon systemic but not upon intracerebroventricular administration in doses that elicited anxiogenic-like behavior and blocked CB1R-induced hypothermia and catalepsy. The peripherally restricted hybrid CB1R antagonist/iNOS inhibitor S-MRI-1867 was also effective in reducing alcohol consumption after oral gavage, while its R enantiomer (CB1R inactive/iNOS inhibitor) was not. The two MRI-1867 enantiomers were equally effective in inhibiting an alcohol-induced increase in portal blood endotoxin concentration that was caused by increased gut permeability. We conclude that (i) activation of peripheral CB1R plays a dominant role in promoting alcohol intake and (ii) the iNOS inhibitory function of MRI-1867 helps in mitigating the alcohol-induced increase in endotoxemia. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Raphael Mechoulam: The Father of Cannabinoid and Endocannabinoid Research)

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Figure 1
Effect of central administration of rimonabant on CP 55,940-induced catalepsy and hypothermia in mice. (a,b) Pharmacologically naïve Cnr1−/− (ko) mice and wild-type littermates (wt) were injected with CP 55,940 (0.1, 0.3, 1 and 3 mg/kg; i.p.) at 30 min intervals. Body temperature (a) and cataleptic behavior (b) were evaluated before administering the next dose of CP 55,940. The respective baseline body temperature in wt and ko groups prior to CP 55,940 injection were 37.1 ± 0.3 °C (n = 3) and 37.2 ± 0.3 °C (n = 3). Mice held the bar for 0.3 ± 0.3 s and 0.3 ± 0.3 s in wt and ko groups, respectively. (c,d) Conscious freely moving C57BL/6J mice (n = 5 animals per treatment group) were infused intracerebroventricularly (i.c.v.) with rimonabant (2 µg, R) or its solvent (V), followed 30 min later by intraperitoneal (i.p.) injection of CP 55,940 (0.1 or 0.3 mg/kg). Another 30 min passed before the hypothermic (c) and cataleptic (d) responses were measured. The respective baseline body temperatures before CP 55,940 injection to V- and R-infused groups were 37.6 ± 0.1 °C and 37.5 ± 0.1 °C (n = 10). Mice held the bar for 0.3 ± 0.3 s and 0.1 ± 0.1 s in V- and R-treated groups, respectively. Results are means ± s.e.m. ** p < 0.01, *** p < 0.01 compared to Cnr1−/− mice (a,b); * p < 0.05, ** p < 0.01 compared to vehicle (c,d). Full article ">Figure 2
Intracerebroventricular microinfusion of JD5037 increases anxiety-related behavior in the elevated plus maze test. Heat maps (a) and summary of mouse activities in individual compartments (b–g) of the elevated plus maze. Animals received i.c.v. infusion of JD5037 (1 µg; JD) or its vehicle (3% DMSO, 8% Tween 80, 30% PEG-400, 59% saline; V). They were tested in the elevated plus maze 1 h later. The computerized EthoVision video tracking system was used for data collection and analysis. Bars are mean ± s.e.m. * p < 0.05, ** p < 0.01, compared with vehicle. Full article ">Figure 3
Relative involvement of central vs. peripheral CB1R blockade in the inhibition of voluntary ethanol intake by CB1 antagonists. Mice had access to 20% ethanol for 4 h each day. On day 4, one hour before the dark period, mice were infused intracerebroventricularly (i.c.v.) with (a) rimonabant (2 µg, RIM, R), (b) JD5037 (1 μg, JD) or their solvents (veh, V) and drinking session was repeated one more time. Another cohort of wild-type mice (wt) and/or their CB1 receptor-deficient (Cnr−/−) counterparts received (c) rimonabant (10 mg/kg), (d) JD5037 (3 mg/kg), or vehicle by oral gavage. Drinking behavior in individual animals is expressed as points before (average of days 1–3) and after treatment (day 4). The corresponding serum ethanol values are shown as mean ± s.e.m. * p < 0.05; *** p < 0.001, compared with before treatment (Student’s t-test for paired samples), # p < 0.05 compared with the vehicle (Student’s t-test for unpaired samples), n.s. not significant. Full article ">Figure 4
MRI-1867 decreases alcohol consumption after oral administration in two drinking models. (a) C57BL/6J mice had access to 20% ethanol for 4 h daily. On day 4, one hour before the dark period, mice received S-1867, (3, 10 mg/kg; S), R-MRI-1867 (10 mg/kg; R), or vehicle (V) by oral gavage and drinking session was repeated. Serum level of acetaldehyde and alcohol from blood obtained at the end of the drinking session. (b) Mice had free access to a 15% ethanol solution and water, using a two-bottle free-choice paradigm. From days 6 to 10, mice received daily S-MRI-1867 (3, 10 mg/kg; S), R-MRI-1867 (10 mg/kg; R), or vehicle (V) by oral gavage. Drinking behavior in individual animals (a) is expressed as points before (average of days 1–3) and after treatment (day 4). Other points and bars (a,b) are mean ± s.e.m. of daily to 5-day drinking behavior, respectively. ** p < 0.01, *** p < 0.001, compared with before treatment (Student’s t-test for paired samples) (a) or with vehicle (two-way ANOVA followed by Tukey’s multiple comparisons test) (b); # p < 0.05, ## p < 0.01, ### p < 0.001 compared to vehicle (one-way ANOVA followed by Dunnett’s post hoc test), n.s. not significant. Full article ">Figure 5
The iNOS inhibitor R-MRI-1867 decreases serum endotoxin level in acutely alcohol-intoxicated mice. Mice received S-MRI-1867 10 mg/kg (S) or R-MRI-1867 10 mg/kg (R) or vehicle (veh) by oral gavage (time 0), followed by intragastric administration of 6 g/kg ethanol (30% w/v; EtOH) or saline at 30 min. Endotoxin was measured in the serum obtained from the portal vein 1 h after the acute alcohol challenge. Results are expressed as mean ± s.e.m. * p < 0.05, ** p < 0.01, compared with vehicle in alcohol-treated group (one-way ANOVA followed by Dunnett’s post hoc test), # p < 0.05, compared with saline-treated mice. Full article ">

10 pages, 2154 KiB

Open AccessArticle

Egg Case Protein 3: A Constituent of Black Widow Spider Tubuliform Silk

by Mikayla Shanafelt, Camille Larracas, Simmone Dyrness, Ryan Hekman, Coby La Mattina-Hawkins, Taylor Rabara, Wilson Wu and Craig A. Vierra

Molecules 2021, 26(16), 5088; https://doi.org/10.3390/molecules26165088 - 22 Aug 2021

Cited by 4 | Viewed by 2702

Abstract

Spider silk has outstanding mechanical properties, rivaling some of the best materials on the planet. Biochemical analyses of tubuliform silk have led to the identification of TuSp1, egg case protein 1, and egg case protein 2. TuSp1 belongs to the spidroin superfamily, containing [...] Read more.

Spider silk has outstanding mechanical properties, rivaling some of the best materials on the planet. Biochemical analyses of tubuliform silk have led to the identification of TuSp1, egg case protein 1, and egg case protein 2. TuSp1 belongs to the spidroin superfamily, containing a non-repetitive N- and C-terminal domain and internal block repeats. ECP1 and ECP2, which lack internal block repeats and sequence similarities to the highly conserved N- and C-terminal domains of spidroins, have cysteine-rich N-terminal domains. In this study, we performed an in-depth proteomic analysis of tubuliform glands, spinning dope, and egg sacs, which led to the identification of a novel molecular constituent of black widow tubuliform silk, referred to as egg case protein 3 or ECP3. Analysis of the translated ECP3 cDNA predicts a low molecular weight protein of 11.8 kDa. Real-time reverse transcription–quantitative PCR analysis performed with different silk-producing glands revealed ECP3 mRNA is predominantly expressed within tubuliform glands of spiders. Taken together, these findings reveal a novel protein that is secreted into black widow spider tubuliform silk. Full article

(This article belongs to the Special Issue Silk Fibroin Materials 2.0)

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Figure 1
General workflow for isolation of the tubuliform gland, egg sac, and dope (liquid removed from the tubuliform glands), followed by analysis of the tryptic peptides by MS/MS analysis. Full article ">Figure 2
SEM images of black widow spider egg case silk reveal two different diameter fibers: (A) 180× magnification; (B) 4000× magnification. Full article ">Figure 3
Venn diagram representing number of proteins expressed in tubuliform glands, liquid spinning dope, and egg sacs, along with a pie chart of percentages of proteins expressed in the tubuliform gland categorized into several different molecular and cellular functions: (A) Venn diagram; (B) pie chart. Full article ">Figure 4
Tandem MS analysis of tryptic fragments generated from in-solution digestion of tubuliform spinning dope identifies the presence of a CRP4 peptide sequence, VVGPFPICDYGLR, and peptide sequence of an uncharacterized protein, SQGNVAMSSSQAGYG QGQSYSSNYAATGDSGTGQGGYSSMR. (A) HCD (MS/MS) spectrum of CRP4 precursor ion with MH+ m/z 1271.74 supports the presence of CRP4 in spinning dope; (B) CID (MS/MS) spectrum of the uncharacterized protein’s precursor ion with MH+ m/z 4041.68 supports the presence of ECP3 in spinning dope. Y- and b-ions and their corresponding masses are shown above the peaks. Full article ">Figure 5
Translation of the gene sequence of GenBank accession number HQ005929.1 predicts a low molecular weight protein with 116 amino acids. Blue text corresponds to peptide sequences identified by MS/MS studies. Yellow coloration denotes a putative secretion signal sequence identified by the SignalP-5.0 server [<a href="#B28-molecules-26-05088" class="html-bibr">28</a>]. Full article ">Figure 6
ECP3 mRNA is expressed in the highest levels in the tubuliform gland but has lower levels relative to ECP2 mRNA: (A) real-time RT-PCR analysis of ECP3 transcript levels in six different silk-producing glands; (B) real-time RT-PCR analysis of ECP2 and ECP3 mRNA levels in the five different silk-producing glands and fat tissue. Full article ">

17 pages, 2936 KiB

Open AccessArticle

Redox Conversions of 5-Methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4triazolo[1,5-a]pyrimidinide L-Arginine Monohydrate as a Promising Antiviral Drug

by Alexandra Ivoilova, Ludmila V. Mikhalchenko, Anton Tsmokalyuk, Marina Leonova, Andrey Lalov, Polina Mozharovskaia, Alisa N. Kozitsina, Alla V. Ivanova and Vladimir L. Rusinov

Molecules 2021, 26(16), 5087; https://doi.org/10.3390/molecules26165087 - 22 Aug 2021

Cited by 10 | Viewed by 2442

Abstract

This article presents the results of a study of electrochemical transformations in aqueous and aprotic media of 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidinide l-arginine monohydrate (1a, Triazid) obtained by electrochemical methods and ESR spectroscopy. The effect of pH on the current and the reduction potential of [...] Read more.

This article presents the results of a study of electrochemical transformations in aqueous and aprotic media of 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidinide l-arginine monohydrate (1a, Triazid) obtained by electrochemical methods and ESR spectroscopy. The effect of pH on the current and the reduction potential of 1a in an aqueous Britton–Robinson buffer solution was studied. It was found that 1a is irreversibly reduced in aqueous acidic media on a glassy carbon electrode in one stage with the participation of six electrons and the formation of 5-methyl-6-amino-7-oxo-1,2,4-triazolo[1,5-a]pyrimidin. The electroreduction of 1a in DMF on a background of tetrabutylammonium salts proceeds in two stages, controlled by the kinetics of second-order reactions. In the first stage, the reduction of 1a is accompanied by protonation by the initial compound of the basic intermediate products formed in the electrode reaction (self-protonation mechanism). The second quasi-reversible stage of the electroreduction 1a corresponds to the formation of a dianion radical upon the reduction of the heterocyclic anion 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidin, which is formed upon the potentials of the first peak. The ESR spectrum of the radical dianion was recorded upon electroreduction of Triazid in the presence of Bu₄NOH. The effect of the formation of ion pairs on the reversibility of the second peak of the 1a transformation is shown. A change in the rate and regioselectivity of the protonation of the dianion radical in the presence of Na⁺ and Li⁺ ions is assumed. The results of studying the electroreduction of 1a by ESR spectroscopy with a TEMPO trap make it possible to assume the simultaneous formation of both a nitroxyl radical and a radical with the spin density localized on the nitrogen at the 4 position of the six-membered ring. Full article

(This article belongs to the Special Issue The Chemistry of Nitrocompounds)

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12 pages, 3493 KiB

Open AccessArticle

Synthesis of Hybrid Organic-Inorganic Hydrotalcite-Like Materials Intercalated with Duplex Herbicides: The Characterization and Simultaneous Release Properties

by Sheikh Ahmad Izaddin Sheikh Mohd Ghazali, Is Fatimah and Farah Liyana Bohari

Molecules 2021, 26(16), 5086; https://doi.org/10.3390/molecules26165086 - 22 Aug 2021

Cited by 7 | Viewed by 2136

Abstract

In this study, a controlled-release formulation of duplex herbicides, namely, 2,4,5-trichlorophenoxybutyric acid (TBA) and 3,4-dichlorophenoxy-acetic acid (3,4D), was simultaneously embedded into Zn-Al-layered double hydroxides (LDHs). The resulting nanohybrid Zinc-Aluminium-3,4D-TBA (ZADTX) was composed of a well-ordered crystalline layered structure with increasing basal spacing from [...] Read more.

In this study, a controlled-release formulation of duplex herbicides, namely, 2,4,5-trichlorophenoxybutyric acid (TBA) and 3,4-dichlorophenoxy-acetic acid (3,4D), was simultaneously embedded into Zn-Al-layered double hydroxides (LDHs). The resulting nanohybrid Zinc-Aluminium-3,4D-TBA (ZADTX) was composed of a well-ordered crystalline layered structure with increasing basal spacing from 8.9 Å to 20.0 Å in the Powder X-ray Diffraction (PXRD) with 3,4D and TBA anions located in the gallery of LDHs with bilayer arrangement. The release of 3,4D and TBA fit the pseudo-second-order model. This duplex nanohybrid possessed a well-controlled release property (53.4% release from TBA and 27.8% release from 3,4D), which was highly effective, requiring the use of a small quantity and, hence, environmentally safer. Full article

(This article belongs to the Special Issue New Applications of Layered Double Hydroxide-Based Materials)

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13 pages, 3249 KiB

Open AccessArticle

Synergistic Catalysis of SnO₂/Reduced Graphene Oxide for VO²⁺/VO₂⁺ and V²⁺/V³⁺ Redox Reactions

by Yongguang Liu, Yingqiao Jiang, Yanrong Lv, Zhangxing He, Lei Dai and Ling Wang

Molecules 2021, 26(16), 5085; https://doi.org/10.3390/molecules26165085 - 22 Aug 2021

Cited by 6 | Viewed by 2537

Abstract

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO₂/reduced graphene oxide (SnO₂/rGO) composite was prepared [...] Read more.

In spite of their low cost, high activity, and diversity, metal oxide catalysts have not been widely applied in vanadium redox reactions due to their poor conductivity and low surface area. Herein, SnO₂/reduced graphene oxide (SnO₂/rGO) composite was prepared by a sol–gel method followed by high-temperature carbonization. SnO₂/rGO shows better electrochemical catalysis for both redox reactions of VO²⁺/VO₂⁺ and V²⁺/V³⁺ couples as compared to SnO₂ and graphene oxide. This is attributed to the fact that reduced graphene oxide is employed as carbon support featuring excellent conductivity and a large surface area, which offers fast electron transfer and a large reaction place towards vanadium redox reaction. Moreover, SnO₂ has excellent electrochemical activity and wettability, which also boost the electrochemical kinetics of redox reaction. In brief, the electrochemical properties for vanadium redox reactions are boosted in terms of diffusion, charge transfer, and electron transport processes systematically. Next, SnO₂/rGO can increase the energy storage performance of cells, including higher discharge electrolyte utilization and lower electrochemical polarization. At 150 mA cm⁻², the energy efficiency of a modified cell is 69.8%, which is increased by 5.7% compared with a pristine one. This work provides a promising method to develop composite catalysts of carbon materials and metal oxide for vanadium redox reactions. Full article

(This article belongs to the Special Issue Design and Application Based on Versatile Nano-Composites)

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15 pages, 1511 KiB

Open AccessArticle

An Efficient Synthesis of 2-CF₃-3-Benzylindoles

by Vasiliy M. Muzalevskiy, Zoia A. Sizova and Valentine G. Nenajdenko

Molecules 2021, 26(16), 5084; https://doi.org/10.3390/molecules26165084 - 22 Aug 2021

Cited by 5 | Viewed by 2685

Abstract

The reaction of α-CF₃-β-(2-nitroaryl) enamines with benzaldehydes afforded effectively α,β-diaryl-CF₃-enones having nitro group. Subsequent reduction of nitro group by NH₄HCO₂-Pd/C system initiated intramolecular cyclization to give 2-CF₃-3-benzylindoles. Target products can be prepared in [...] Read more.

The reaction of α-CF₃-β-(2-nitroaryl) enamines with benzaldehydes afforded effectively α,β-diaryl-CF₃-enones having nitro group. Subsequent reduction of nitro group by NH₄HCO₂-Pd/C system initiated intramolecular cyclization to give 2-CF₃-3-benzylindoles. Target products can be prepared in up to quantitative yields. Broad synthetic scope of the reaction was shown. Probable mechanism of indole formation is proposed. Full article

(This article belongs to the Special Issue The Chemistry of Nitrocompounds)

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21 pages, 11500 KiB

Open AccessArticle

Synthesis of 3,5-Bis(trifluoromethyl)phenyl-Substituted Pyrazole Derivatives as Potent Growth Inhibitors of Drug-Resistant Bacteria

by Ibrahim S. Alkhaibari, Hansa Raj KC, Subrata Roy, Mohd. K. Abu-gazleh, David F. Gilmore and Mohammad A. Alam

Molecules 2021, 26(16), 5083; https://doi.org/10.3390/molecules26165083 - 22 Aug 2021

Cited by 6 | Viewed by 2945

Abstract

Enterococci and methicillin-resistant S. aureus (MRSA) are among the menacing bacterial pathogens. Novel antibiotics are urgently needed to tackle these antibiotic-resistant bacterial infections. This article reports the design, synthesis, and antimicrobial studies of 30 novel pyrazole derivatives. Most of the synthesized compounds are [...] Read more.

Enterococci and methicillin-resistant S. aureus (MRSA) are among the menacing bacterial pathogens. Novel antibiotics are urgently needed to tackle these antibiotic-resistant bacterial infections. This article reports the design, synthesis, and antimicrobial studies of 30 novel pyrazole derivatives. Most of the synthesized compounds are potent growth inhibitors of planktonic Gram-positive bacteria with minimum inhibitory concertation (MIC) values as low as 0.25 µg/mL. Further studies led to the discovery of several lead compounds, which are bactericidal and potent against MRSA persisters. Compounds 11, 28, and 29 are potent against S. aureus biofilms with minimum biofilm eradication concentration (MBEC) values as low as 1 µg/mL. Full article

(This article belongs to the Special Issue Recent Advances in the Synthesis and Biological Studies of Five-Membered Azaheterocycle Derivatives)

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15 pages, 2612 KiB

Open AccessArticle

Synthesis of Catechol Derived Rosamine Dyes and Their Reactivity toward Biogenic Amines

by Filipe Monteiro-Silva, Carla Queirós, Andreia Leite, María T. Rodríguez, María J. Rojo, Tomás Torroba, Rui C. Martins, Ana M. G. Silva and Maria Rangel

Molecules 2021, 26(16), 5082; https://doi.org/10.3390/molecules26165082 - 22 Aug 2021

Cited by 4 | Viewed by 3585

Abstract

Functional organic dyes play a key role in many fields, namely in biotechnology and medical diagnosis. Herein, we report two novel 2,3- and 3,4-dihydroxyphenyl substituted rosamines (3 and 4, respectively) that were successfully synthesized through a microwave-assisted protocol. The best reaction [...] Read more.

Functional organic dyes play a key role in many fields, namely in biotechnology and medical diagnosis. Herein, we report two novel 2,3- and 3,4-dihydroxyphenyl substituted rosamines (3 and 4, respectively) that were successfully synthesized through a microwave-assisted protocol. The best reaction yields were obtained for rosamine 4, which also showed the most interesting photophysical properties, specially toward biogenic amines (BAs). Several amines including n- and t-butylamine, cadaverine, and putrescine cause spectral changes of 4, in UV–Vis and fluorescence spectra, which are indicative of their potential application as an effective tool to detect amines in acetonitrile solutions. In the gas phase, the probe response is more expressive for spermine and putrescine. Additionally, we found that methanolic solutions of rosamine 4 and n-butylamine undergo a pink to yellow color change over time, which has been attributed to the formation of a new compound. The latter was isolated and identified as 5 (9−aminopyronin), whose solutions exhibit a remarkable increase in fluorescence intensity together with a shift toward more energetic wavelengths. Other 9-aminopyronins 6a, 6b, 7a, and 7b were obtained from methanolic solutions of 4 with putrescine and cadaverine, demonstrating the potential of this new xanthene entity to react with primary amines. Full article

(This article belongs to the Special Issue Pigment, Dye, and Green Colorant Research in Europe)

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Full article ">Figure 1
Chemical structures of the biogenic amines used in the studies, RhB and rosamines 1–4. Full article ">Figure 2
Comparison of the absorbance (A) and emission intensity (B) spectra of 4 toward 2 equiv. of n-butylamine (n-But, red line), t-butylamine (t-But, blue line), putrescine (Put, green line), and cadaverine (Cad, magenta line) in solution (acetonitrile, 25 °C). Full article ">Figure 3
Absorption (A) and emission (B) spectra of 4 upon the addition (0–8 equiv.) of putrescine in CH3CN (the inset graphs represent the variation in absorbance (left) and fluorescence intensity (right) for the wavelengths that display more intensity variation (512, 551, and 649 nm; 574 nm, respectively). |4| = 35 μM and λexc = 551 nm. Full article ">Figure 4
Comparison of the fluorescence intensity change of 4 toward BA in the gas phase at λexc 533 nm. Probe 4 in red, Probe 4 + BA in blue, and Probe 4 + Controls (air, N2 and water vapor) in grey. Full article ">Figure 5
Reactivity of rosamine 4 with n-butylamine. (A) Scheme of the reaction of rosamine 4 with n-butylamine leading to the formation of 9-aminopyronin 5. Rosamine 4 itself is weakly fluorescent due to the intramolecular PET quenching (left hand-side cuvette). However, after reaction with n-butylamine and chromatographic purification, 9-aminopyronin 5 can be isolated, which exhibits strong fluorescence (right hand-side cuvette); (B) 1H NMR spectrum of 5 in methanol-d4, * denote solvent peaks (chloroform and methanol); (C) ESI-MS spectrum of 5. Full article ">Scheme 1
Synthetic route to obtain rosamines 1–4. Full article ">Scheme 2
Reaction involving the nucleophilic attack of alkylamines to 4, leading to aminopyronin 5, 6a, 6b, 7a and 7b. Full article ">

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