| 1. |
- Messinger, Johannes, 1963-, et al.
(författare)
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S-3 state of the water oxidase in photosystem II
- 1997
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 36:23, s. 6862-6873
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the reductant hydrazine on the flash-induced oxygen oscillation patterns of spinach thylakoids was used to characterize a new super-reduced redox state of the water oxidase in photosystem II. The formation of a discrete S-3 state is evident from the shift of the first maximum of oxygen evolution from the 3rd flash through the 5th flash to the 7th flash during a 90 min incubation of dark-adapted thylakoids with 10 mM hydrazine sulfate at pH 6.8 on ice. A distinct period four oscillation with further maxima on the 11th and 15th flashes is still observed at this stage of the incubation. The data analysis within the framework of an extended Kok model reveals that a S-3 state population of almost 50% can be achieved by this treatment. A prolonged incubation of the S-3 sample with 10 mM hydrazine (and even 100 mM) does not lead to a further shift of the first maximum toward the 9th flash that could reflect the formation of the S-5 state. Instead, a slow oxidation of S-3 to S-2 takes place by an as yet unidentified electron acceptor. A consistent simulation of all the measured oxygen oscillation patterns of this study could, however, only be achieved by including the formal redox states S-4 and S-5 in the fits (S-4 + S-5 up to 35%). The implications of these findings for the oxidation states of the manganese in the tetranuclear cluster of the water oxidase are discussed.
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| 2. |
- Cao, J. S., et al.
(författare)
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Quantum biology revisited
- 2020
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 6:14
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.
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| 3. |
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| 4. |
- Isgandarova, S, et al.
(författare)
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Functional differences of photosystem II from Synechococcus elongatus and spinach characterized by flash induced oxygen evolution patterns
- 2003
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 42:30, s. 8929-8938
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Tidskriftsartikel (refereegranskat)abstract
- Detailed comparative studies of flash induced oxygen evolution patterns in thylakoids from the thermophilic cyanobacterium Synechococcus elongatus (S. elongatus; also referred to as Thermosynechococcus elongatus) and from spinach led to the following results: (i) the miss parameter cc of S. elongatus thylakoids exhibits a pronounced temperature dependence with a minimum of 7% at 25 degreesC and values of 17 and 10% at 3 and 35 degreesC, respectively, while for spinach thylakoids alpha decreases continuously from 18% at 35 degreesC down to 8% at 3 degreesC; (ii) at all temperatures, the double hit probability exceeds in S. elongatus the corresponding values of spinach by an increment Deltabeta of about 3%; (iii) at 20 degreesC the slow relaxation of the oxidation states S-2 and S-3 is about 15 and 30 times, respectively, slower in S. elongatus than in spinach, while the reduction of these S states by tyrosine Y-D is 2-3 times faster; (iv) the reaction SOYDox --> S1YD is slower by a factor of 4 in S. elongatus as compared to spinach; and (v) the activation energies of S state dark relaxations in S. elongatus are all within a factor of 1.5 as compared to the previously reported values from spinach thylakoids [Vass, I., Deak, Z., and Hideg, E. (1990) Biochim. Biophys. Acta 1017, 63-69; Messinger, J., Schroder, W. P., and Renger, G. (1993) Biochemistry 32, 7658-7668], but the difference between the activation energies of the Slow S-2 and S-3 decays is significantly larger in S. elongatus than in spinach. These results are discussed in terms of differences between cyanobacteria and higher plants on the acceptor side of PSII and a shift of the redox potential of the couple Y-D/Y-D(ox). The obtained data are also suitable to address questions about effects of the redox state of Y-D on the miss probability and the possibility of an S state dependent miss parameter.
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| 5. |
- KEBEKUS, U, et al.
(författare)
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STRUCTURAL-CHANGES IN THE WATER-OXIDIZING COMPLEX MONITORED VIA THE PH-DEPENDENCE OF THE REDUCTION RATE OF REDOX STATE S-1 BY HYDRAZINE AND HYDROXYLAMINE IN ISOLATED SPINACH THYLAKOIDS
- 1995
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 34:18, s. 6175-6182
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Tidskriftsartikel (refereegranskat)abstract
- A detailed kinetic analysis is presented for the pH dependence of the reduction of the water-oxidizing complex (WOC) in redox state S-1 by hydrophilic amines NH(2)R (R = NH2, OH) in suspensions of isolated thylakoids. Measurements of patterns of the oxygen yield induced by a train of single-turnover flashes and evaluation of the data within the framework of an extended Kok model [Messinger, J., Wacker, U., and Renger, G. (1991) Biochemistry 30, 7852-7862] led to the following results: (a) the rate constants k(s1)(NH(2)R) exhibit strikingly similar pH dependencies for NH2OH and NH2NH2 with ''titration waves'' at pH 5.3-5.6; 6.2-6.5, and above a critical pH value of about 7.4; (b) the differences in the reaction mechanism between NH2OH (1-electron reduction) and NH2NH2 (2-electron reduction) are almost pH-independent; (c) the ratio of the rate constants, k(s1)(NH2OH)/k(s1)(NH2NH2), decreases by a factor of about 9 within the range 5 < pH < 8.5. A detailed analysis reveals that these data cannot be consistently explained by the assumption that the unprotonated forms NH2OH and NH2NH2 are the active species while the protonated cations [NH3OH](+) and [N2H5](+) are nonreactive. A quantitative description is achieved by the additional postulate that pH-dependent structural changes take place in the WOC, thereby modulating the reactivity toward exogenous redox active amines of the type NH(2)R. On the basis of the results of this study and a recent report [Messinger, J., and Renger, G. (1994) Biochemistry 33, 10896-10905], it is inferred that the WOC undergoes three specific structural changes, with characteristic pH values of 5.3-5.5,6.2-6.5, and above 7.4.
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| 6. |
- Messinger, Johannes, 1963-, et al.
(författare)
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ANALYSES OF PH-INDUCED MODIFICATIONS OF THE PERIOD-4 OSCILLATION OF FLASH-INDUCED OXYGEN EVOLUTION REVEAL DISTINCT STRUCTURAL-CHANGES OF THE PHOTOSYSTEM-II DONOR SIDE AT CHARACTERISTIC PH VALUES
- 1994
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 33:36, s. 10896-10905
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a thorough analysis of the reaction pattern of flash-induced oxygen evolution in spinach thylakoids as a function of pH (4.5 I pH I 9) and the redox state of tyrosine Y-D in polypeptide D2. Evaluation of the experimental data within the conventional Kok model [Kok, B., Forbush, B., and McGloin, M. (1970) Photochem. Photobiol. 11, 457-475] led to the following results: (1) the probability of the miss factor is strongly pH dependent (with a pronounced minimum near neutral pH) while the double hit factor is less affected; (2) a marked increase of the apparent S-0 population arises at alkaline pH in dark-adapted samples where most of the Y-D is reduced, but this effect is absent if the percentage of PS II containing the oxidized form Y-D(ox) is high; and (3) the lifetimes of S-2 and S-3 exhibit a characteristic pH dependence that is indicative of conformational changes of functional relevance within the water-oxidizing complex and its environment; (4) the kinetic interaction of redox states S-2 and S-3 With Y-D is characterized by a change of its behavior at a threshold pH of 6.5-7.0; and (5) at acidic pH values the extent of S-2 and S-3 reduction by Y-D decreases concomitant with the occurrence of a very fast decay kinetics. On the basis of a detailed discussion of these results and data from the literature, the water oxidase is inferred to undergo structural changes at pH values of 5-5.5 and 6.5-7.0. These transitions are almost independent of the redox state S-i and modify the reaction coordiates of the water oxidase toward endogenous reductants.
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| 7. |
- Messinger, Johannes, 1963-, et al.
(författare)
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GENERATION, OXIDATION BY THE OXIDIZED FORM OF THE TYROSINE OF POLYPEPTIDE D2, AND POSSIBLE ELECTRONIC CONFIGURATION OF THE REDOX STATE-S(0), STATE-S-1, AND STATE-S-2 OF THE WATER OXIDASE IN ISOLATED SPINACH THYLAKOIDS
- 1993
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Ingår i: Biochemistry. - TECH UNIV BERLIN,MAX VOLMER INST BIOPHYS & PHYS CHEM,STR 17 JUNI 135,D-10623 BERLIN,GERMANY. : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 32:36, s. 9379-9386
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Tidskriftsartikel (refereegranskat)abstract
- Suitable treatment of thylakoids with hydrazine permits a high population of the redox states S0, S-1, and S-2 in the water oxidase. Experiments performed with dark-adapted samples enriched either in the oxidized or reduced form of the redox-active tyrosine, Y(D), of PolYpeptide D2 reveal that Y(D)ox is a unique endogenous oxidant within the PS II complex which causes a one-electron abstraction from the water oxidase in states S0, S-1, and S-2, respectively. A kinetic analysis of the period four oscillation of oxygen yield induced by a train of short flashes in dark-adapted samples permits the determination of the rate constants of electron abstraction from the reduced water oxidase by Y(D)ox. A value of 9 x 10(-4) s-1 was found for the oxidation of S0 and S-2, while S-1 becomes oxidized with a rate constant of 4 x 10(-4) s-1 at 20-degrees-C and pH 7.2. The redox state S0 generated either from S1 via the three-flash-induced oxidative pathway through S4 or from a one-flash oxidation of the S-1 state obtained by S1 reduction with NH2NH2 exhibits the same kinetics as S0 oxidation by Y(D)ox. On the basis of these findings and data taken from the literature, the electronic configuration of the Manganese atoms in the tetranuclear cluster is discussed. It is assumed that the dimer model of two binuclear manganese groups within the tetranuclear cluster comprises a functional heterogeneity: (i) one binuclear center, referred to as the catalytic group, is proposed to be involved in the oxidative pathway leading to the eventual oxidation of water to dioxygen, and (ii) the other binuclear center, symbolized as component C, is redox-inert during the oxidative pathway but can be reduced by exogenous (and endogenous?) components, thereby forming the states S-1 and S-2 Of the water oxidase. An asymmetric protein matrix around the tetranuclear manganese cluster is assumed to be responsible for the functional heterogeneity of the manganese centers.
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| 8. |
- Messinger, Johannes, 1963-, et al.
(författare)
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STRUCTURE-FUNCTION RELATIONS IN PHOTOSYSTEM-II - EFFECTS OF TEMPERATURE AND CHAOTROPIC AGENTS ON THE PERIOD 4 OSCILLATION OF FLASH-INDUCED OXYGEN EVOLUTION
- 1993
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Ingår i: Biochemistry. - TECH UNIV BERLIN,MAX VOLMER INST BIOPHYS & PHYS CHEM,STR 17 JUNI 135,D-10623 BERLIN,GERMANY. : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 32:30, s. 7658-7668
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Tidskriftsartikel (refereegranskat)abstract
- The characteristic period four oscillation patterns of oxygen evolution induced by a train of single-turnover flashes were measured in dark-adapted samples as a function of temperature and upon addition of chaotropic agents. The following results were obtained: (a) Within the range of 0 < theta < 35-degrees-C, the ratio of the oxygen yield induced by the 4th and 3rd flashes of the train, Y4/Y3, and the oxygen yield induced by the 2nd flash, Y2, exhibit similar dependencies on the temperature in isolated thylakoids, PS II membrane fragments, and inside-out vesicles. (b) Below a characteristic temperature theta(c) of 20-25-degrees-C, the values of Y4/Y3 and Y2, which reflect (at constant S0 dark population) the probabilities of misses and double hits, respectively, remain virtually independent of temperature, whereas above theta(c) these parameters increase. (c) The dark decays of S2 and S3 via fast and slow kinetics due to reduction of the water oxidase by Y(D) and other endogenous electron donor(s), respectively, exhibit comparatively strong temperature dependencies in thylakoids with the following activation energies: E(A)(S2fast) = 55 kJ/mol, E(A)(S3fast) = 50 kJ/mol, E(A)(S2slow) = 85 kJ/mol, and E(A)(S3slow) = 75 kJ/mol. The activation energy of S0 oxidation to S1 by Y(D)ox was found to be markedly smaller with a value of E(A)(S0) = 30 kJ/mol. (d) Incubation with chaotropic agents at concentrations which do not significantly impair the oxygen evolution capacity leads to modifications of the oscillation pattern with remarkable differences for various types of agents: Tris and urea are practically without effect; guanidine hydrochloride affects Y4/Y3 in a similar way as elevated temperature but without significant changes of Y2 and the decay kinetics of S2 and S3; and anions of the Hofmeister series (SCN-, ClO4-, I-) cause a drastic destabilization of Y(D)ox. Possible structure-function relations of the PS II complex are discussed on the basis of these findings.
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| 9. |
- Messinger, Johannes, 1963-, et al.
(författare)
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THE REACTIVITY OF HYDRAZINE WITH PHOTOSYSTEM-II STRONGLY DEPENDS ON THE REDOX STATE OF THE WATER OXIDIZING SYSTEM
- 1990
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Ingår i: FEBS Letters. - : ELSEVIER SCIENCE BV. - 0014-5793 .- 1873-3468. ; 277:1-2, s. 141-146
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Tidskriftsartikel (refereegranskat)abstract
- The decay kinetics of the redox states S2 and S3 of the water-oxidizing enzyme have been analyzed in isolated spinach thylakoids in the absence and presence of the exogenous reductant hydrazine. In control samples without NH2NH2 a biphasic decay is observed. The rapid decline of S2 and S3 with Y(D) as reductant exhibits practically the same kinetics with t1/2 = 6-7 s at pH = 7.2 and 7-degrees-C. The slow reduction (order of 5-10 min at 7-degrees-C) of S2 and S3 with endogenous electron donors other than Y(D) is about twice as fast for S2 as for S3 under these conditions. In contrast, the hydrazine-induced reductive shifts of the formal redox states S(i) (i = 0 ... 3) are characterized by a totally different kinetic pattern: (a) at 1 mM NH2NH2 and incubation on ice the decay of S2 is estimated to be at least 25 times faster (t1/2 less-than-or-equal-to 0.4 min) than the corresponding reaction of S3 (t1/2 almost-equal-to 13 min); (b) the NH2NH2-induced decay of S3 is even slower (about twice) than the transformation of S1 into the formal redox state 'S-1' (t1/2 almost-equal-to 6 min), which gives rise to the two-digit phase shift of the oxygen-yield pattern induced by a flash train in dark adapted thylakoids. (c) the NH2NH2-induced transformation S0-->'S-2' [Renger, Messinger and Hanssum (1990) in: Curr. Res. Photosynth. (Baltscheffsky, M., ed) Vol. 1, pp. 845-848, Kluwer, Dordrecht] is about three times faster (t1/2 almost-equal-to 2 min) than the reaction S1 [GRAPHICS] 'S-1'. Based on these results, the following dependence on the redox state S(i) of the reactivity towards NH2NH2 is obtained: S3 < S1 < S0 < < S2. The implications of this surprising order of reactivity are discussed.
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| 10. |
- Messinger, Johannes, 1963-, et al.
(författare)
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UNUSUAL LOW REACTIVITY OF THE WATER OXIDASE IN REDOX STATE S3 TOWARD EXOGENOUS REDUCTANTS - ANALYSIS OF THE NH2OH-INDUCED AND NH2NH2-INDUCED MODIFICATIONS OF FLASH-INDUCED OXYGEN EVOLUTION IN ISOLATED SPINACH THYLAKOIDS
- 1991
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 30:31, s. 7852-7862
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Tidskriftsartikel (refereegranskat)abstract
- The effect of redox-active amines NH2R (R = OH or NH2) on the period-four oscillation pattern of oxygen evolution has been analyzed in isolated spinach thylakoids as a function of the redox state S(i) (i = 0, ..., 3) of the water oxidase. The following results were obtained: (a) In dark-adapted samples with a highly populated S1 state, NH2R leads via a dark reaction sequence to the formal redox state "S-1"; (b) the reaction mechanism is different between the NH2R species; NH2OH acts as a one-electron donor, whereas NH2NH2 mainly functions as a two-electron donor, regardless of the interacting redox state S(i) (i = 0, ..., 3). For NH2NH2, the modified oxygen oscillation patterns strictly depend upon the initial ratio [S0(0)]/[S1(0)] before the addition of the reductant; while due to kinetic reasons, for NH2OH this dependence largely disappears after a short transient period. (c) The existence of the recently postulated formal redox state "S-2" is confirmed not only in the presence of NH2NH2 [Renger, G., Messinger, J., & Hanssum, B. (1990) in Current Research in Photosynthesis (Baltscheffsky, M., Ed.) Vol. 1, pp 845-848, Kluwer, Dordrecht] but also in the presence of NH2OH. (d) Activation energies, E(A), of 50 kJ/mol were determined for the NH2R-induced reduction processes that alter the oxygen oscillation pattern from dark-adapted thylakoids. (e) Although marked differences exist between NH2OH and NH2NH2 in terms of the reduction mechanism and efficiency (which is about 20-fold in favor of NH2OH), both NH2R species exhibit the same order of rate constants as a function of the redox state S(i) in the nonperturbed water oxidase: kNH2R(S0) > kNH2R(S1) << kNH2R(S2) >> kNH2R(S3) The large difference between S2 and S3 in their reactivity toward NH2R is interpreted to indicate that a significant change in the electronic configuration and nuclear geometry occurs during the S2 --> S3 transition that makes the S3 state much less susceptible to NH2R. The implications of these findings are discussed with special emphasis on the possibility of complexed peroxide formation in redox state S3 postulated previously on the basis of theoretical considerations [Renger, G. (1978) in Photosynthetic Water Oxidation (Metzner, H., Ed.) pp 229-248, Academic Press, London].
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| 11. |
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| 12. |
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| 13. |
- Sarrou, J, et al.
(författare)
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Nitric oxide-induced formation of the S-2 state in the oxygen-evolving complex of photosystem II from Synechococcus elongatus
- 2003
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 42:4, s. 1016-1023
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Tidskriftsartikel (refereegranskat)abstract
- In spinach photosystem II (PSII) membranes, the tetranuclear manganese cluster of the oxygen-evolving complex (OEC) can be reduced by incubation with nitric oxide at -30 degreesC to a state which is characterized by an Mn-2(II, III) EPR multiline signal [Sarrou, J., Ioannidis, N., Deligiannakis, Y., and Petrouleas, V. (1998) Biochemistry 37, 3581-3587]. This state was recently assigned to the S-2 state of the OEC [Schansker, G., Goussias, C., Petrouleas, V., and Rutherford, A. W. (2002) Biochemistry 41, 3057-3064]. On the basis of EPR spectroscopy and flash-induced oxygen evolution patterns, we show that a similar reduction process takes place in PSII samples of the thermophilic cyanobacterium Synechococcus elongatus at both -30 and 0 degreesC. An EPR multiline signal, very similar but not identical to that of the S-2 state in spinach, was obtained with monomeric and dimeric PSII core complexes from S. elongatus only after incubation at -30 degreesC. The assignment of this EPR multiline signal to the S-2 state is corroborated by measurements of flash-induced oxygen evolution patterns and detailed fits using extended Kok models. The small reproducible shifts of several low-field peak positions of the S-2 EPR multiline signal in S. elongatus compared to spinach suggest that slight differences in the coordination geometry and/or the ligands of the manganese cluster exist between thermophilic cyanobacteria and higher plants.
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| 14. |
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| 15. |
- van Soest, Annick P. M., et al.
(författare)
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DHA status influences effects of B-vitamin supplementation on cognitive ageing : a post-hoc analysis of the B-proof trial
- 2022
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Ingår i: European Journal of Nutrition. - : Springer Nature. - 1436-6207 .- 1436-6215. ; 61:7, s. 3731-3739
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Trials aiming to lower homocysteine by B-vitamin supplementation have reported mixed results on slowing cognitive decline. We investigated if efficacy of B-vitamin supplementation is affected by baseline plasma omega-3 fatty acid levels. Methods This post-hoc analysis of the B-proof trial included 191 adults aged 65 years or older with baseline plasma total homocysteine >= 12 mu mol/L, randomly assigned to 400 mu g folic acid and 500 mu g vitamin B12 or placebo daily for 2 years. Global and domain-specific cognitive functioning were assessed at baseline and after 2 years. The effect of B-vitamin supplementation was analyzed according to tertiles of baseline plasma omega-3 fatty acids concentrations combined, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) individually using multiple linear regression analyses. Results The mean +/- SD age of the participants was 71.6 +/- 5.9 years and median [IQR] Mini-Mental State Examination was 29 [28-30]. The treatment effect of B-vitamins on global cognition was larger in participants in the high compared to the middle DHA tertile (difference in z-score, mean +/- SE 0.22 +/- 0.10, p = 0.03). There was no significant interaction between B-vitamin supplementation and combined omega-3 fatty acid (p = 0.49) and EPA (p = 0.99) tertiles. Similarly, the efficacy of B-vitamin treatment on domain-specific cognitive functioning did not link to omega-3 fatty acid, DHA, or EPA plasma levels. Conclusion This post-hoc analysis indicated that efficacy of B-vitamin supplementation in slowing cognitive decline relates to DHA status, with individuals with higher plasma DHA levels benefitting more from vitamin B12 and folic acid use. The results support earlier observations that positive effects of B-vitamins in cognitive ageing may be subgroup-specific.
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