pheophytin-a and neoxanthin

Fucoxanthin and its derivatives are the main light-harvesting pigments in the photosynthetic apparatus of many chromalveolate algae and represent the most abundant carotenoids in the world's oceans, thus being major facilitators of marine primary production. A central step in fucoxanthin biosynthesis that has been elusive so far is the conversion of violaxanthin to neoxanthin. Here, we show that in chromalveolates, this reaction is catalyzed by violaxanthin de-epoxidase-like (VDL) proteins and that VDL is also involved in the formation of other light-harvesting carotenoids such as peridinin or vaucheriaxanthin. VDL is closely related to the photoprotective enzyme violaxanthin de-epoxidase that operates in plants and most algae, revealing that in major phyla of marine algae, an ancient gene duplication triggered the evolution of carotenoid functions beyond photoprotection toward light harvesting.

Topics: Algal Proteins; Aquatic Organisms; Carotenoids; Chlorophyll A; Gene Expression Regulation; Light-Harvesting Protein Complexes; Oxidoreductases; Phaeophyceae; Phylogeny; Xanthophylls

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

The ecological importance and diversity of pico/nanoplanktonic algae remains poorly studied in marine waters, in part because many are tiny and without distinctive morphological features. Amongst green algae, Mamiellophyceae such as Micromonas or Bathycoccus are dominant in coastal waters while prasinophytes clade VII, yet not formerly described, appear to be major players in open oceanic waters. The pigment composition of 14 strains representative of different subclades of clade VII was analyzed using a method that improves the separation of loroxanthin and neoxanthin. All the prasinophytes clade VII analyzed here showed a pigment composition similar to that previously reported for RCC287 corresponding to pigment group prasino-2A. However, we detected in addition astaxanthin for which it is the first report in prasinophytes. Among the strains analyzed, the pigment signature is qualitatively similar within subclades A and B. By contrast, RCC3402 from subclade C (Picocystis) lacks loroxanthin, astaxanthin, and antheraxanthin but contains alloxanthin, diatoxanthin, and monadoxanthin that are usually found in diatoms or cryptophytes. For subclades A and B, loroxanthin was lowest at highest light irradiance suggesting a light-harvesting role of this pigment in clade VII as in Tetraselmis.

Topics: Carotenoids; Chlorophyll; Chlorophyll A; Chlorophyta; Light; Lutein; Oceans and Seas; Photosynthesis; Pigments, Biological; Xanthophylls; Zeaxanthins

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

Measurement of the second hyperpolarizability (γ) values of compounds can provide insight into the molecular structural requirements for enhancement of third harmonic generation (THG) signal. A convenient method for measuring the γ of compounds in solutions was developed by implementing the THG ratio method which is based on measuring the THG intensity from two interfaces using a nonlinear optical microscope while accounting for the refractive index of solutions at the fundamental and third harmonic wavelengths. We demonstrated that the difference in refractive index at both wavelengths strongly influenced the calculation of γ values when compounds have absorption near the third harmonic or fundamental wavelength. To this end, a refractometer with the wavelength tuning range from UV to near IR was constructed, and the measured refractive indices were used to extract the γ values. The γ values of carotenoids and chlorophylls found in photosynthetic pigment-protein complexes were explored. Large differences in the refractive index at third harmonic and fundamental wavelengths for chlorophylls result in γ values that are more than two orders of magnitude larger than γ values for carotenoids as well as the sign of chlorophylls'γ values is negative while carotenoids have positive γ values.

Topics: Absorption; Carotenoids; Chlorophyll; Chlorophyll A; Microscopy; Refractometry; Solutions; Xanthophylls

The response of Norway spruce saplings (Picea abies [L.] Karst.) was monitored continuously during short-term exposure (10 days) to high irradiance (HI; 1000micromol m(-2)s(-1)). Compared with plants acclimated to low irradiance (100micromol m(-2)s(-1)), plants after HI exposure were characterized by a significantly reduced CO(2) assimilation rate throughout the light response curve. Pigment contents varied only slightly during HI exposure, but a rapid and strong response was observed in xanthophyll cycle activity, particularly within the first 3 days of the HI treatment. Both violaxanthin convertibility under HI and the amount of zeaxanthin pool sustained in darkness increased markedly under HI conditions. These changes were accompanied by an enhanced non-radiative dissipation of absorbed light energy (NRD) and the acceleration of induction of both NRD and de-epoxidation of the xanthophyll cycle pigments. We found a strong negative linear correlation between the amount of sustained de-epoxidized xanthophylls and the photosystem II (PSII) photochemical efficiency (F(V)/F(M)), indicating photoprotective down-regulation of the PSII function. Recovery of F(V)/F(M) at the end of the HI treatment revealed that Norway spruce was able to cope with a 10-fold elevated irradiance due particularly to an efficient NRD within the PSII antenna that was associated with enhanced violaxanthin convertibility and a light-induced accumulation of zeaxanthin that persisted in darkness.

Topics: Absorption; Carbon Dioxide; Chlorophyll; Chlorophyll A; Electron Transport; Epoxy Compounds; Fluorescence; Light; Lutein; Norway; Photosynthesis; Photosystem II Protein Complex; Picea; Time Factors; Xanthophylls; Zeaxanthins

Six plant pigments separated by paper chromatography have been measured by photoacoustic spectroscopy (PAS). Their PA spectra are compared with the corresponding absorption spectra, which indicate that PAS is a convenient and effective method for identifying plant pigment. The sorts of marine algae are numerous and pigments in marine algae have certain characteristics. The PA spectra of green, red and brown algae have been reported. Pigment characteristics in these algae are identified by their second derivative PA spectra.

Topics: Acoustics; beta Carotene; Chlorophyll; Chlorophyll A; Chromatography, Paper; Eukaryota; Light; Lutein; Photochemistry; Pigments, Biological; Plants; 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