chlorophyll-b and neoxanthin

In the photic zone, phytoplankton experience diurnal variation in light intensity. However, prolonged exposure to aphotic condition influences their physiological state. Pigment composition is a useful biomarker to decipher cells physiological state and adaptive response to changing environmental conditions. Chlorophyll, a natural pigment, is biosynthesised even in darkness and studies have shown this ability is determined by genetic characteristics of an organism. The purpose of this study was to examine the influence of darkness on pigments and chlorophyll autofluorescence of Tetraselmis indica. Dark exposure (up to 6 months) had no significant impact on chlorophyll a and b concentration, whereas carotenoids were enhanced. Upon re-illumination pigments gradually recovered to pre-dark phase condition. These adaptive survival strategies of T. indica by altering pigment concentration in response to prolonged darkness are interesting. The absence of loroxanthin and loroxanthin esters in T. indica is reported in a first Tetraselmis species so far. In addition, the evaluation of autofluorescence and cellular chlorophyll concentration pointed out that they are not interdependent in this species. Hence, careful consideration of these two factors is needed when either of them is used as a proxy for other. The results obtained encourage a thorough study of pigment analysis, especially when subjected to darkness, to elucidate potential role in the evolution, chemotaxonomy, and survivability of species.

Topics: Carotenoids; Chlorophyll; Chlorophyll A; Chlorophyta; Chromatography, High Pressure Liquid; Darkness; Pigments, Biological; Spectrometry, Fluorescence; Time Factors; Xanthophylls

Resonance Raman spectroscopy was used to evaluate the structure of light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCII), reconstituted from wild-type (WT) and mutant apoproteins over-expressed in Escherichia coli. The point mutations involved residue S123, exchanged for either P (S123P) or G (S123G). In all reconstituted proteins, lutein 2 displayed a distorted conformation, as it does in purified LHCII trimers. Reconstituted WT and S123G also exhibited a conformation of bound neoxanthin (Nx) molecules identical to the native protein, while the S123P mutation was found to induce a change in Nx conformation. This structural change of neoxanthin is accompanied by a blue shift of the absorption of this carotenoid molecule. The interactions assumed by (and thus the structure of the binding sites of) the bound Chls b were found identical in all the reconstituted proteins, and only marginally perturbed as compared to purified LHCII. The interactions assumed by bound Chls a were also identical in purified LHCII and the reconstituted WT. However, the keto carbonyl group of one Chl a, originally free-from-interactions in WT LHCII, becomes involved in a strong H-bond with its environment in LHCII reconstituted from the S123P apoprotein. As the absorption in the Qy region of this protein is identical to that of the LHCII reconstituted from the WT apoprotein, we conclude that the interaction state of the keto carbonyl of Chl a does not play a significant role in tuning the binding site energy of these molecules.

Topics: Binding Sites; Chlorophyll; Chlorophyll A; Light-Harvesting Protein Complexes; Lutein; Mutation; Photosystem II Protein Complex; Spectrum Analysis, Raman; Xanthophylls

The antioxidant activity and individual bioactive compounds of lettuce, cultivated with 2.5-30% (v/v) of fresh or composted espresso spent coffee grounds, were assessed. A progressive enhancement of lettuce's antioxidant capacity, evaluated by radical scavenging effect and reducing power, was exhibited with the increment of fresh spent coffee amounts, while this pattern was not so clear with composted treatments. Total reducing capacity also improved, particularly for low spent coffee concentrations. Additionally, very significant positive correlations were observed for all carotenoids in plants from fresh spent coffee treatments, particularly for violaxanthin, evaluated by HPLC. Furthermore, chlorophyll a was a good discriminating factor between control group and all spent coffee treated samples, while vitamin E was not significantly affected. Espresso spent coffee grounds are a recognised and valuable source of bioactive compounds, proving herein, for the first time, to potentiate the antioxidant pool and quality of the vegetables produced.

Topics: Antioxidants; Carotenoids; Chlorophyll; Chlorophyll A; Chromatography, High Pressure Liquid; Coffee; Crops, Agricultural; Fertilizers; Lactuca; Lutein; Plant Extracts; Soil; Tocopherols; Xanthophylls

The electric-field induced absorption changes (Stark effect) of reconstituted light-harvesting complex II (LHCII) in different oligomerisation states-monomers and trimers-with different xanthophyll content have been probed at 77 K. The Stark spectra of the reconstituted control samples, containing the xanthophylls lutein and neoxanthin, are very similar to previously reported spectra of native LHCII. Reconstituted LHCII, containing lutein but no neoxanthin, shows a similar electrooptical response in the Chl a region, but the Stark signal of Chl b around 650 nm amounts to at most approximately 25% of that of the control samples. We conclude that neoxanthin strongly modifies the electronic states of the nearby Chl b molecules causing a large electrooptical response at 650 nm stemming from one or more Chls b in the control samples. Ambiguities about the assignment of several bands in the Soret region [Biochim. Biophys. Acta 1605 (2003) 83] are resolved and the striking difference in electric field response between the two lutein molecules is confirmed. The Stark effect in the carotenoid spectral region in both control and neoxanthin-deficient samples is almost identical, showing that the neoxanthin Stark signal is small and much less intense than the lutein Stark signal.

Topics: Carotenoids; Chlorophyll; Light-Harvesting Protein Complexes; Lutein; Photosystem II Protein Complex; Plant Proteins; Plants; Recombinant Proteins; Spectrum Analysis; Xanthophylls

The major light-harvesting complex of photosystem II can be reconstituted in vitro from its bacterially expressed apoprotein with chlorophylls a and b and neoxanthin, violaxanthin, lutein, or zeaxanthin as the only xanthophyll. Reconstitution of these one-carotenoid complexes requires low-stringency conditions during complex formation and isolation. Neoxanthin complexes (containing 30-50% of the all-trans isomer) disintegrate during electrophoresis, exhibit a largely reduced resistance against proteolytic attack; in addition, energy transfer from Chl b to Chl a is easily disrupted at elevated temperature. Complexes reconstituted in the presence of either zeaxanthin or lutein contain nearly two xanthophylls per 12 chlorophylls and are more resistant against trypsin. Lutein-LHCIIb also exhibits an intermediate maintenance of energy transfer at higher temperature. Violaxanthin complexes approach a xanthophyll/12 chlorophyll ratio of 3, similar to the ratio in recombinant LHCIIb containing all xanthophylls. On the other hand, violaxanthin-LHCIIb exhibits a low thermal stability like neoxanthin complexes, but an intermediate accessibility towards trypsin, similar to lutein-LHCIIb and zeaxanthin-LHCIIb. Binary competition experiments were performed with two xanthophylls at varying ratios in the reconstitution. Analysis of the xanthophyll contents in the reconstitution products yielded information about relative carotenoid affinities of three assumed binding sites. In lutein/neoxanthin competition experiments, two binding sites showed a strong preference (> 200-fold) for lutein, whereas the third binding site had a higher affinity (25-fold) to neoxanthin. Competition between lutein and violaxanthin gave a similar result, although the specificities were lower: two binding sites have a 36-fold preference for lutein and one has a fivefold preference for violaxanthin. The lowest selectivity was between lutein and zeaxanthin: two binding sites had a fivefold higher affinity for lutein and one has a threefold higher affinity to zeaxanthin.

Topics: Apoproteins; beta Carotene; Binding Sites; Binding, Competitive; Carotenoids; Chlorophyll; Chlorophyll A; Electrophoresis, Polyacrylamide Gel; Energy Transfer; Light-Harvesting Protein Complexes; Lutein; Photosynthetic Reaction Center Complex Proteins; Photosystem II Protein Complex; Pigments, Biological; Plant Proteins; Plants; Protein Precursors; Substrate Specificity; Trypsin; Xanthophylls; Zeaxanthins

Fourteen different revertants of Chlamydomonas reinhardtii recovered with ability of biosynthesis chlorophyll b were hybridized with wile-type strain, and tetrad analysis with random sampling was performed. It appeared that sub genes resulting in cbnI gene to reverse mutation, and localize on the first chromosome. According to its linkage that differences, 5 strains carrying various mutant alleles of suppressor genes were determined. Forward hybridological analysis demonstrated that the sub genes were absent of allelic specificity and had a single genic character in response to suppression. Phenotypic analysis of the sub/Sub diplontic hybrid have verified the dominant character of mutant sub genes. The phenomenon of present various allelic sub genes and all its characters revealed that the possibility of several ways or various regulatory means exists in biosynthesis of chlorophyll b.

Topics: Animals; Carotenoids; Chlamydomonas reinhardtii; Chlorophyll; Genes, Suppressor; Mutation; Xanthophylls