There is growing evidence that eukaryotic microalgae can become a more sustainable and profitable... more There is growing evidence that eukaryotic microalgae can become a more sustainable and profitable alternative than terrestrial crops to produce feed, fuels, and valuable coproducts. The major factor driving progress in algal biomass production is the potential of microalgae to produce substantially greater biomass per unit land area than terrestrial crops. To be financially feasible, however, current algal biomass yields must be increased. Given the fact that algal biomass production is in its infancy there exist multiple opportunities to improve biomass yields. For example, recent bioprospecting efforts have led to the identification of new microalgal strains having biomass yields that compete economically with plant biomass. Substantial increases in biomass yields have also been achieved using advanced genetic engineering approaches. Targeted improvements in photosynthetic efficiency have led to three-fold increases in algal biomass yields. One genetic tool that has seen limited a...
and 2007, its production and acreage tripled across africa and quadrupled in nigeria, the contine... more and 2007, its production and acreage tripled across africa and quadrupled in nigeria, the continent’s and the world’s largest producer (fao, 00 ). SubSaharan africa produced over million tons of fresh roots of cassava in 00 , of which no less than 95% was consumed as food; the starch provides > 5% of dietary energy for an estimated 00 million africans (Dorosh, 00 ). frequent consumers of cassava are at greater risk for malnutrition—especially deficiencies in vitamin-a, iron, and zinc—than consumers of other diets, particularly those that are cereal-based (Gegios et al., 0 0). a nutrition survey in cassava-consuming areas of nigeria and Kenya revealed inadequate intake of vitamin a in 3% and % and inadequate iron intake in 3% and % of pre-school-aged children, respectively (Gegios et al., 0 0). vitamin-a deficiency causes a loss of 9 ,000 disability-adjusted life years (DaLYs1) in nigeria and ,000 DaLYs in Kenya annually; iron deficiency causes loss of 59 ,000 DaLYs in nigeria and...
EPR spectra attributed to the redox active tyrosine residues on the oxidizing side of photosystem... more EPR spectra attributed to the redox active tyrosine residues on the oxidizing side of photosystem II (TyrZ and TyrD) have almost identical line shapes, although the tyrosyl radicals differ in stability and redox characteristics. Strongly modified spectra of oxidized TyrD in site-directed mutants in a histidine residue, H189 on the D2 reaction center protein in the cyanobacterium Synechocystis 6803, support a structural model where H189 interacts closely, probably via a hydrogen bond, to TyrD (Tommos, C., Davidsson, L., Svensson, B., Madsen, C., Vermass, W., and Styring, S. (1993) Biochemistry 32, 5436-5441). To determine whether TyrZ and the corresponding histidine on the D1 protein (D1-H190) interacts similarly, we have generated His-Phe (H190F) and His-Tyr (H190Y) mutations in the C2 symmetry related H190 residue on the D1 reaction center protein by site-directed mutagenesis in Chlamydomonas reinhardtii. The H190F and H190Y mutants assemble photosystem II reaction centers capable of primary photochemistry but unable to oxidize water. We have obtained kinetic spectra of a flash-induced transient EPR signal that we assign to oxidized TyrZ in the D1-H190 mutants. The spectra are identical in line width (18-20 G) and hyperfine structure to the wild-type spectrum from oxidized TyrZ and exhibit decay kinetics (t 1/2 approximately 500 ms) typical for the TyrZ radical in managenese-depleted photosystem II membranes. However, both TyrZ and TyrD were oxidized with reduced (10-15%) quantum yield in these mutants, indicating that the kinetics of electron donation to P+680 were significantly modified as a result of the mutation. Thus, the altered kinetics of TyrZ in the mutants suggest that there is an interaction between TyrZ and His-190 on the D1 protein. However, unlike the situation on the D2 side, the presence of a hydrogen bond between TyrZ and H190 on the D1 protein is improbable.
An unidentified open reading frame, 248 or 255 amino acids in length, on the maize chloroplast DN... more An unidentified open reading frame, 248 or 255 amino acids in length, on the maize chloroplast DNA fragment Bam5 was sequenced. It encodes a protein which contains a high proportion of hydrophilic amino acids, of which 22% are hydroxylated, interrupted by hydrophobic domains. A synthetic peptide corresponding to a hydrophilic sequence was used to generate antibodies. Western blots of photosystem I and II complexes prepared from maize and spinach thylakoids indicate that the psbG gene product is a membrane-associated protein of the photosystem II complex that migrates as a 24-kDa species on polyacrylamide gel electrophoresis.
We examine the dynamics of entanglement entropy of all parts in an open system consisting of a tw... more We examine the dynamics of entanglement entropy of all parts in an open system consisting of a two-level dimer interacting with an environment of oscillators. The dimer-environment interaction is almost energy conserving. We find the precise link between decoherence and production of entanglement entropy. We show that not all environment oscillators carry significant entanglement entropy and we identify the oscillator frequency regions which contribute to the production of entanglement entropy. For energy conserving dimer-environment interactions the models are explicitly solvable and our results hold for all dimer-environment coupling strengths. We carry out a mathematically rigorous perturbation theory around the energy conserving situation in the presence of small non-energy conserving interactions.
As one of the most pervasive environmental problems, Hg pollution in sediment is particularly dif... more As one of the most pervasive environmental problems, Hg pollution in sediment is particularly difficult to remediate because it cannot be decomposed. The application of ultrasound combined with biomass (transgenic Chlamydomonas reinhardtii (C. reinhardtii), a green alga) for the removal of Hg from model and contaminated sediments (Al(2)O(3), α-HgS, and PACS-2 marine sediment) was investigated in this study. Ultrasound was found to enhance Hg release from Al(2)O(3), α-HgS, and PACS-2 marine sediment into the aqueous phase compared to mechanical shaking. A transgenic C. reinhardtii (2AMT-2) expressing a plasmamembrane-anchored metallothionein polymer effectively recovered Hg(II) released into the aqueous phase by sonication over a broad pH range from 2.0 to 9.0. The results showed that this combined technique of ultrasound and alga biomass (2AMT-2) engineered for enhanced metal recovery was effective to remove Hg from solids and sediments, especially from Al(2)O(3) and α-HgS with no natural organic matter. The results of this study are discussed with respect to the development of in situ remediation techniques for Hg-contaminated sediments.
Flash-induced chlorophyll fluorescence kinetics from photosystem II in thylakoids from the dark-g... more Flash-induced chlorophyll fluorescence kinetics from photosystem II in thylakoids from the dark-grown wild type and two site-directed mutants of the D1 protein His190 residue (D1-H190) in Chlamydomonas reinhardtii have been characterized. Induction of the chlorophyll fluorescence on the first flash, reflecting electron transport from YZ to P680(+), exhibited a strong pH dependence with a pK of 7.6 in the dark-grown wild type which lacks the Mn cluster. The chlorophyll fluorescence decay, measured in the presence of DCMU, which reflects recombination between QA- and YZox, was also pH-dependent with a similar pK of 7.5. These results indicate participation by the same base, which is suggested to be D1-H190, in oxidation and reduction of YZ in forward electron transfer and recombination pathways, respectively. This hypothesis was tested in the D1-H190 mutants. Induction of chlorophyll fluorescence in these H190 mutants has been observed to be inefficient due to slow electron transfer from YZ to P680(+) [Roffey, R. A., et al. (1994) Biochim. Biophys. Acta 1185, 257-270]. We show that this reaction is pH-dependent, with a pK of 8. 1, and at pH >/=9, the fluorescence induction is efficient in the H190 mutants, suggesting direct titration of YZ. The efficient oxidation of YZ ( approximately 70% at pH 9.0) at high pH was confirmed by kinetic EPR measurements. In contrast to the wild type, the H190 mutants show little or no observable fluorescence decay. Our data suggest that H190 is an essential component in the electron transfer reactions in photosystem II and acts as a proton acceptor upon YZ oxidation. In the H190 mutants, this reaction is inefficient and YZ oxidation only occurs at elevated pHs when YZ itself probably is deprotonated. We also propose that H190 is able to return a proton to YZox during electron recombination from QA- in a reaction which does not take place in the D1-H190 mutants.
One of the unique features of electron transfer processes in photosystem II (PSII) reaction cente... more One of the unique features of electron transfer processes in photosystem II (PSII) reaction centers (RC) is the exclusive transfer of electrons down only one of the two parallel cofactor branches. In contrast to the RC core polypeptides (psaA and psaB) of photosystem I (PSI), where electron transfer occurs down both parallel redox-active cofactor branches, there is greater protein-cofactor asymmetry between the PSII RC core polypeptides (D1 and D2). We have focused on the identification of protein-cofactor relationships that determine the branch along which primary charge separation occurs (P(680)(+)/pheophytin(-)(Pheo)). We have previously shown that mutagenesis of the strong hydrogen-bonding residue, D1-E130, to less polar residues (D1-E130Q,H,L) shifted the midpoint potential of the Pheo(D1)/Pheo(D1)(-) couple to more negative values, reducing the quantum yield of primary charge separation. We did not observe, however, electron transfer down the inactive branch in D1-E130 mutants. The protein residue corresponding to D1-E130 on the inactive branch is D2-Q129 which presumably has a reduced hydrogen-bonding interaction with Pheo(D2) relative to the D1-E130 residue with Pheo(D1). Analysis of the recent 2.9 Å cyanobacterial PSII crystal structure indicated, however, that the D2-Q129 residue was too distant from the Pheo(D2) headgroup to serve as a possible hydrogen bond donor and directly impact its midpoint potential as well as potentially determine the directionality of electron transfer. Our objective was to characterize the function of this highly conserved inactive branch residue by replacing it with a nonconservative leucine or a conservative histidine residue. Measurements of Chl fluorescence decay kinetics and thermoluminescence studies indicate that the mutagenesis of D2-Q129 decreases the redox gap between Q(A) and Q(B) due to a lowering of the redox potential of Q(B). The resulting increased yield of S(2)Q(B)(-) charge recombination in the D2-Q129 mutants leads to an increased susceptibility to photoinhibitory light presumably due to (3)P(680)-mediated oxidative damage. The results indicate that the D2-Q129 residue plays a critical role in stabilizing the charge-separated state in PSII and further documents the structural and functional asymmetry between the two cofactor branches in PSII.
There is growing evidence that eukaryotic microalgae can become a more sustainable and profitable... more There is growing evidence that eukaryotic microalgae can become a more sustainable and profitable alternative than terrestrial crops to produce feed, fuels, and valuable coproducts. The major factor driving progress in algal biomass production is the potential of microalgae to produce substantially greater biomass per unit land area than terrestrial crops. To be financially feasible, however, current algal biomass yields must be increased. Given the fact that algal biomass production is in its infancy there exist multiple opportunities to improve biomass yields. For example, recent bioprospecting efforts have led to the identification of new microalgal strains having biomass yields that compete economically with plant biomass. Substantial increases in biomass yields have also been achieved using advanced genetic engineering approaches. Targeted improvements in photosynthetic efficiency have led to three-fold increases in algal biomass yields. One genetic tool that has seen limited a...
and 2007, its production and acreage tripled across africa and quadrupled in nigeria, the contine... more and 2007, its production and acreage tripled across africa and quadrupled in nigeria, the continent’s and the world’s largest producer (fao, 00 ). SubSaharan africa produced over million tons of fresh roots of cassava in 00 , of which no less than 95% was consumed as food; the starch provides > 5% of dietary energy for an estimated 00 million africans (Dorosh, 00 ). frequent consumers of cassava are at greater risk for malnutrition—especially deficiencies in vitamin-a, iron, and zinc—than consumers of other diets, particularly those that are cereal-based (Gegios et al., 0 0). a nutrition survey in cassava-consuming areas of nigeria and Kenya revealed inadequate intake of vitamin a in 3% and % and inadequate iron intake in 3% and % of pre-school-aged children, respectively (Gegios et al., 0 0). vitamin-a deficiency causes a loss of 9 ,000 disability-adjusted life years (DaLYs1) in nigeria and ,000 DaLYs in Kenya annually; iron deficiency causes loss of 59 ,000 DaLYs in nigeria and...
EPR spectra attributed to the redox active tyrosine residues on the oxidizing side of photosystem... more EPR spectra attributed to the redox active tyrosine residues on the oxidizing side of photosystem II (TyrZ and TyrD) have almost identical line shapes, although the tyrosyl radicals differ in stability and redox characteristics. Strongly modified spectra of oxidized TyrD in site-directed mutants in a histidine residue, H189 on the D2 reaction center protein in the cyanobacterium Synechocystis 6803, support a structural model where H189 interacts closely, probably via a hydrogen bond, to TyrD (Tommos, C., Davidsson, L., Svensson, B., Madsen, C., Vermass, W., and Styring, S. (1993) Biochemistry 32, 5436-5441). To determine whether TyrZ and the corresponding histidine on the D1 protein (D1-H190) interacts similarly, we have generated His-Phe (H190F) and His-Tyr (H190Y) mutations in the C2 symmetry related H190 residue on the D1 reaction center protein by site-directed mutagenesis in Chlamydomonas reinhardtii. The H190F and H190Y mutants assemble photosystem II reaction centers capable of primary photochemistry but unable to oxidize water. We have obtained kinetic spectra of a flash-induced transient EPR signal that we assign to oxidized TyrZ in the D1-H190 mutants. The spectra are identical in line width (18-20 G) and hyperfine structure to the wild-type spectrum from oxidized TyrZ and exhibit decay kinetics (t 1/2 approximately 500 ms) typical for the TyrZ radical in managenese-depleted photosystem II membranes. However, both TyrZ and TyrD were oxidized with reduced (10-15%) quantum yield in these mutants, indicating that the kinetics of electron donation to P+680 were significantly modified as a result of the mutation. Thus, the altered kinetics of TyrZ in the mutants suggest that there is an interaction between TyrZ and His-190 on the D1 protein. However, unlike the situation on the D2 side, the presence of a hydrogen bond between TyrZ and H190 on the D1 protein is improbable.
An unidentified open reading frame, 248 or 255 amino acids in length, on the maize chloroplast DN... more An unidentified open reading frame, 248 or 255 amino acids in length, on the maize chloroplast DNA fragment Bam5 was sequenced. It encodes a protein which contains a high proportion of hydrophilic amino acids, of which 22% are hydroxylated, interrupted by hydrophobic domains. A synthetic peptide corresponding to a hydrophilic sequence was used to generate antibodies. Western blots of photosystem I and II complexes prepared from maize and spinach thylakoids indicate that the psbG gene product is a membrane-associated protein of the photosystem II complex that migrates as a 24-kDa species on polyacrylamide gel electrophoresis.
We examine the dynamics of entanglement entropy of all parts in an open system consisting of a tw... more We examine the dynamics of entanglement entropy of all parts in an open system consisting of a two-level dimer interacting with an environment of oscillators. The dimer-environment interaction is almost energy conserving. We find the precise link between decoherence and production of entanglement entropy. We show that not all environment oscillators carry significant entanglement entropy and we identify the oscillator frequency regions which contribute to the production of entanglement entropy. For energy conserving dimer-environment interactions the models are explicitly solvable and our results hold for all dimer-environment coupling strengths. We carry out a mathematically rigorous perturbation theory around the energy conserving situation in the presence of small non-energy conserving interactions.
As one of the most pervasive environmental problems, Hg pollution in sediment is particularly dif... more As one of the most pervasive environmental problems, Hg pollution in sediment is particularly difficult to remediate because it cannot be decomposed. The application of ultrasound combined with biomass (transgenic Chlamydomonas reinhardtii (C. reinhardtii), a green alga) for the removal of Hg from model and contaminated sediments (Al(2)O(3), α-HgS, and PACS-2 marine sediment) was investigated in this study. Ultrasound was found to enhance Hg release from Al(2)O(3), α-HgS, and PACS-2 marine sediment into the aqueous phase compared to mechanical shaking. A transgenic C. reinhardtii (2AMT-2) expressing a plasmamembrane-anchored metallothionein polymer effectively recovered Hg(II) released into the aqueous phase by sonication over a broad pH range from 2.0 to 9.0. The results showed that this combined technique of ultrasound and alga biomass (2AMT-2) engineered for enhanced metal recovery was effective to remove Hg from solids and sediments, especially from Al(2)O(3) and α-HgS with no natural organic matter. The results of this study are discussed with respect to the development of in situ remediation techniques for Hg-contaminated sediments.
Flash-induced chlorophyll fluorescence kinetics from photosystem II in thylakoids from the dark-g... more Flash-induced chlorophyll fluorescence kinetics from photosystem II in thylakoids from the dark-grown wild type and two site-directed mutants of the D1 protein His190 residue (D1-H190) in Chlamydomonas reinhardtii have been characterized. Induction of the chlorophyll fluorescence on the first flash, reflecting electron transport from YZ to P680(+), exhibited a strong pH dependence with a pK of 7.6 in the dark-grown wild type which lacks the Mn cluster. The chlorophyll fluorescence decay, measured in the presence of DCMU, which reflects recombination between QA- and YZox, was also pH-dependent with a similar pK of 7.5. These results indicate participation by the same base, which is suggested to be D1-H190, in oxidation and reduction of YZ in forward electron transfer and recombination pathways, respectively. This hypothesis was tested in the D1-H190 mutants. Induction of chlorophyll fluorescence in these H190 mutants has been observed to be inefficient due to slow electron transfer from YZ to P680(+) [Roffey, R. A., et al. (1994) Biochim. Biophys. Acta 1185, 257-270]. We show that this reaction is pH-dependent, with a pK of 8. 1, and at pH >/=9, the fluorescence induction is efficient in the H190 mutants, suggesting direct titration of YZ. The efficient oxidation of YZ ( approximately 70% at pH 9.0) at high pH was confirmed by kinetic EPR measurements. In contrast to the wild type, the H190 mutants show little or no observable fluorescence decay. Our data suggest that H190 is an essential component in the electron transfer reactions in photosystem II and acts as a proton acceptor upon YZ oxidation. In the H190 mutants, this reaction is inefficient and YZ oxidation only occurs at elevated pHs when YZ itself probably is deprotonated. We also propose that H190 is able to return a proton to YZox during electron recombination from QA- in a reaction which does not take place in the D1-H190 mutants.
One of the unique features of electron transfer processes in photosystem II (PSII) reaction cente... more One of the unique features of electron transfer processes in photosystem II (PSII) reaction centers (RC) is the exclusive transfer of electrons down only one of the two parallel cofactor branches. In contrast to the RC core polypeptides (psaA and psaB) of photosystem I (PSI), where electron transfer occurs down both parallel redox-active cofactor branches, there is greater protein-cofactor asymmetry between the PSII RC core polypeptides (D1 and D2). We have focused on the identification of protein-cofactor relationships that determine the branch along which primary charge separation occurs (P(680)(+)/pheophytin(-)(Pheo)). We have previously shown that mutagenesis of the strong hydrogen-bonding residue, D1-E130, to less polar residues (D1-E130Q,H,L) shifted the midpoint potential of the Pheo(D1)/Pheo(D1)(-) couple to more negative values, reducing the quantum yield of primary charge separation. We did not observe, however, electron transfer down the inactive branch in D1-E130 mutants. The protein residue corresponding to D1-E130 on the inactive branch is D2-Q129 which presumably has a reduced hydrogen-bonding interaction with Pheo(D2) relative to the D1-E130 residue with Pheo(D1). Analysis of the recent 2.9 Å cyanobacterial PSII crystal structure indicated, however, that the D2-Q129 residue was too distant from the Pheo(D2) headgroup to serve as a possible hydrogen bond donor and directly impact its midpoint potential as well as potentially determine the directionality of electron transfer. Our objective was to characterize the function of this highly conserved inactive branch residue by replacing it with a nonconservative leucine or a conservative histidine residue. Measurements of Chl fluorescence decay kinetics and thermoluminescence studies indicate that the mutagenesis of D2-Q129 decreases the redox gap between Q(A) and Q(B) due to a lowering of the redox potential of Q(B). The resulting increased yield of S(2)Q(B)(-) charge recombination in the D2-Q129 mutants leads to an increased susceptibility to photoinhibitory light presumably due to (3)P(680)-mediated oxidative damage. The results indicate that the D2-Q129 residue plays a critical role in stabilizing the charge-separated state in PSII and further documents the structural and functional asymmetry between the two cofactor branches in PSII.
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Papers by Richard Sayre