Photoprotective efficiency of lutein, zeaxanthin and violaxanthin in liposomes made of digalactosyldiacylglycerol (DGDG) has been investigated. It was found that zeaxanthin is about ten times more effective than the two other xanthophylls in inhibition of chlorophyll a photo-oxidation. Kinetics of chlorophyll photobleaching suggests that exceptional photoprotective efficacy of zeaxanthin in membranes consists in effective scavenging of free radicals. High photoprotective efficiency of zeaxanthin in membranes correlates with its physiological function.
The four-membered cycle of enzymatic reactions with repression of enzyme synthesis in the presence of cyclic symmetry is presented. Experimental premises, formulation of the model, analytical analysis, bifurcations diagrams and numerical solutions are shown. By Hopf bifurcation theory, the conditions of oscillations were found for two kinds of the model: fully symmetric and extended one. The latter of them reconstructs better the experimental results than the former one. The models are more general and can be related to rings of coupled biological oscillators.
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