Search results for "Photos"
showing 10 items of 701 documents
Water-depth effects in photosynthetic pigment content of the benthic algae Dictyota dichotoma and Udotea petiolata
1981
Abstract The effect of water depth on the light-harvesting pigments contents in Dictyota dichotoma (Hudson) Lamouroux and Udotea petiolata (Turra) Borgesen was studied. Both species showed higher photosynthetic-pigments contents with increased depth or shade. The ratios of chlorophyll c /chlorophyll a and chlorophyll b / chlrophyll a in D. dichotoma and U. petiolata were lower in light-exposed samples. In D. dichotoma , the ratios of fucoxanthin to chlorophyll a increased with depth or shade; however, it is worth noting that the 0 m (sun) samples showed the highest values. On the other hand, total carotenoids to chlorophyll a ratios in U. petiolata increased with depth.
Response to ozone in two lettuce varieties on chlorophyll a fluorescence, photosynthetic pigments and lipid peroxidation.
2004
The effect of different O3 concentrations on two lettuce (Lactuca sativa L.) varieties (Valladolid and Morella) was investigated through chlorophyll (Chl) a fluorescence parameters, photosynthetic pigments (Chl a, b and total carotenoid), lipid peroxidation and crop yield. Ozone fumigation caused: a decrease in maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) in mature leaves, a reduction in the non-cyclic electron flow (phiPSII) and a lower capacity to reoxidize the QA pool (qP). These reductions were significant in the Valladolid var. but not in the Morella var. A significant decrease in Chl a, b and in the total carotenoids was observed in the Valladolid var. but not…
Pigment composition of PS II pigment protein complexes purified by anion exchange chromatography. identification of xanthophyll cycle pigment binding…
1997
Summary The pigment composition of the chlorophyll binding proteins of Photosystem II (PS II) of spinach ( Spinacea oleracea L.) has been determined using sucrose gradient ultracentrifugation, anion exchange chromatography and HPLC based pigment analysis. The xanthophyll cycle pigments violaxanthin, antheraxanthin and zeaxanthin were exclusively found in the proteins of the outer PS II antenna, with the highest amounts being present in the minor chlorophyll alb binding proteins CP 29 and CP 26. PS II core particles containing the reaction centre proteins D1, D2, cytochrome b 559 and the proteins of the inner antenna CP 47 and CP 43 bind β-carotene as the only carotenoid. The presence of the…
Carotenoids
2009
Publisher Summary This chapter provides an overview of what is known about carotenoid metabolism in Chlamydomonas with reference to other green algae and vascular plants. The biosynthesis of carotenoids and the subdivisions of carotenogenesis are described. With respect to subcellular distribution, the carotenoids in vegetative cells localize to the chloroplast where they either serve as photosynthetic pigments bound to the protein complexes of the two photosystems, or as components of the eyespot apparatus is outlined with its functional significance. Carotenoids can serve as precursors of a number of other molecules with important physiological functions in Chlamydomonas.
Chapter 16 Folding and Pigment Binding of Light-Harvesting Chlorophyll a/b Protein (LHCIIb)
2010
The major light-harvesting chlorophyll a/b protein (LHCIIb) is one of the most abundant proteins of the chloroplast in green plants. It contains roughly half of the chlorophylls involved in photosynthesis, and exhibits an unusual ability to self-organize in vitro. Simply mixing the apoprotein, native or recombinant, with its pigments, chlorophyll a, chlorophyll b, and xanthophylls, in detergent solution, suffices to trigger protein folding and the assembly of about 18 pigments in their correct binding sites. A study of the mechanism of this self-organization seems worthwhile since (1) our knowledge about membrane protein folding is scarce compared to what we know about the folding of water-…
Effect of phosphatydylcholine on spectral properties and photostability of 3,3′-diethyloxadicarbocyanine iodide (DODCI) — a potent anti-tumor photose…
1998
Abstract The potential anti-tumor photosensitizer 3,3′-diethyloxadicarbocyanine iodide (DODCI) has been immobilized in dimyristoyl phosphatidylcholine (DMPC) vesicles. Binding of the dicarbocyanine to the lipid vesicles induces several changes in the electronic absorption, emission and excitation spectra of the dye. The monomeric dye molecules exist in at least two forms when immobilized in the DMPC liposomes and the non-luminescing H-aggregates of the dye show efficient excitation energy transfer to the DODCI monomers. Entrapment of the dye in the liposomes generally decreases the photostability of DODCI. While emission from singlet oxygen (1O2) has not been recorded, indirect results sugg…
De-epoxidation of Violaxanthin after Reconstitution into Different Carotenoid Binding Sites of Light-harvesting Complex II
2001
In higher plants, the de-epoxidation of violaxanthin (Vx) to antheraxanthin and zeaxanthin is required for the pH-dependent dissipation of excess light energy as heat and by that process plays an important role in the protection against photo-oxidative damage. The de-epoxidation reaction was investigated in an in vitro system using reconstituted light-harvesting complex II (LHCII) and a thylakoid raw extract enriched in the enzyme Vx de-epoxidase. Reconstitution of LHCII with varying carotenoids was performed to replace lutein and/or neoxanthin, which are bound to the native complex, by Vx. Recombinant LHCII containing either 2 lutein and 1 Vx or 1.6 Vx and 1.1 neoxanthin or 2.8 Vx per mono…
The Binding of Xanthophylls to the Bulk Light-harvesting Complex of Photosystem II of Higher Plants
2002
The pigment composition of the light-harvesting complexes (LHCs) of higher plants is highly conserved. The bulk complex (LHCIIb) binds three xanthophyll molecules in combination with chlorophyll (Chl) a and b. The structural requirements for binding xanthophylls to LHCIIb have been examined using an in vitro reconstitution procedure. Reassembly of the monomeric recombinant LHCIIb was performed using a wide range of native and nonnative xanthophylls, and a specific requirement for the presence of a hydroxy group at C-3 on a single β-end group was identified. The presence of additional substituents (e.g.at C-4) did not interfere with xanthophyll binding, but they could not, on their own, supp…
Assembly of the Major Light-harvesting Chlorophyll-a/b Complex
2006
The major light-harvesting chlorophyll-a/b complex in most higher plants contains three carotenoids, lutein, neoxanthin, and violaxanthin. How these pigments are assembled into the complex during its biogenesis is largely unknown. Here we show that neoxanthin but not lutein can dissociate from the fully assembled complex. Its equilibrium binding constant in a detergent system (0.1% n-dodecyl-beta-D-maltoside) was determined to be > or = 10(6) m(-1). Neoxanthin insertion into light-harvesting chlorophyll-a/b complex prefolded from overexpressed apoprotein (Lhcb1*2 from Pisum sativum) in the presence of chlorophylls a, b, and lutein as the sole carotenoid is kinetically controlled by an activ…
Photosensitive properties of composite films based on copper chloride in polymer matrix
2013
The composite films based on PMMA and CuCl2 were prepared. Transmission spectra of the films before and after illumination by different laser lines (405, 448, 456 nm) were measured. The reversible character of the composite photosensitivity was fixed. The phenomenon of direct surface relief formation after laser beam illumination of composite films was described. The holographic gratings were recorded by different exposure (200 – 500 J/cm2) in the films with different concentration (8 and 20 wt. %) of copper salt. The film sensitivity dependence on polymer molecular weight was studied. Surface relief of the gratings was measured by AFM.