We observed that the unstable 13, 17-cyclopheophorbide a enol is one of the most abundant pigments in recent sediments (Black Sea, Mediterranean Sea, Peru margin) and here we report its isolation and structure determination (high-performance liquid chromatography, ultraviolet-visible spectrometry, mass spectrometry, and nuclear magnetic resonance). This enol has been considered as the precusor ...

The aggregation dependent correlation between fluorescence quenching and the electronic carotenoid– chlorophyll interactions, / S1 Chl Coupling , as measured by comparing chlorophyll fluorescence observed after twoand one-photon excitation, has been investigated using native LHC II samples as well as mutants lacking Chl 2 and Chl 13. For native LHC II the same linear correlation between / S1 Ch...

The efficiency of chemical energy production of a photosynthetic system can be strongly enhanced in the presence of metal nanoparticles. Two competing effects contribute to the photosystem efficiency: plasmon enhancement of photon fields inside the light-absorbing chlorophyll molecules and energy transfer from chlorophylls to metal nanoparticles. The first effect can lead to strong enhancement ...

Chitosan is a natural polymer, which has been used in agriculture to stimulate crop growth. Furthermore, it has been used for the encapsulation of nanoparticles in order to obtain controlled release. In this work, the effect of chitosan-PVA and Cu nanoparticles (Cu NPs) absorbed on chitosan-PVA on growth, antioxidant capacity, mineral content, and saline stress in tomato plants was evaluated. T...

Stimulated emission and lasing have been demonstrated for chlorophyll a, chlorophyll b, and bacteriochlorophyll a as well as for the Mg-free chlorophyll derivatives pheophytin a and methyl pheophorbide a. Population inversion was obtained by optically pumping with an N(2) laser. For the three chlorophylls, lasing was observed for only the (0,0) vibronic region of the S(1) --> S(0) fluorescence ...

Excitation spectra of chlorophyll fluorescence from intact rye leaves were registered at dif­ ferent steps of the induction of photosynthesis after dark adaptation. Analysis of these spectra indicates that at least two processes related to spectroscopic features are responsible for a flu­ orescence quenching. The first one, active during the first 100 s of illumination, was interpret­ ed to con...

Analyses were made of chlorophyll a and b and fatty acids (18:3, 18:2, 18:1, 18:0, 16:2, 16:1, and 16:0) of greening and senescing leaf tissue. Those dark-grown tissues given a prior treatment of red, far red, or red followed by far red light showed similar increases in chlorophylls and linolenate (18:3) when exposed to continuous white light. In contrast, green barley (Hordeum vulgare L.) leav...

Chlorophylls are essential cofactors for photosynthesis, which sustains global food chains and oxygen production. Billions of tons of chlorophylls are synthesized annually, yet full understanding of chlorophyll biosynthesis has been hindered by the lack of characterization of the Mg-protoporphyrin IX monomethyl ester oxidative cyclase step, which confers the distinctive green color of these pig...

Tomato plants were grown hydroponically under different deficient regimes of nitrogen (N) and phosphorus (P) in the form of nitrate and phosphate. Results showed a severe reduction in growth, soluble protein and chlorophylls contents under N deficiency, which suggested accelerating of leaf senescence. Furthermore, it was accompanied by enhanced activity of peroxidase and sugars contents that we...

The plant light-harvesting complex of photosystem II (LHC-II) collects and transmits solar energy for photosynthesis in chloroplast membranes and has essential roles in regulation of photosynthesis and in photoprotection. The 2.5 A structure of pea LHC-II determined by X-ray crystallography of stacked two-dimensional crystals shows how membranes interact to form chloroplast grana, and reveals t...