chlorophyll-b and violaxanthin

Dandelion (Taraxacum officinale) var. Garnet Stem was harvested from Texas and New Jersey for identification, quantification of phytochemicals, measurement of free radical scavenging activity, and bile acid binding capacity. The red midrib and petioles were extracted with methanol or ethanol and with or without water in combination with four different acids such as formic, hydrochloric, acetic, and citric acid. LC-ESI-HR-QTOF-MS was used to identify four anthocyanins including cyanidin-3-glucoside, cyanidin-3-(6-malonyl)-glucoside (A-1), cyanidin-3-(6-malonyl)-glucoside (A-2), and peonidin-3-(malonyl)-glucoside for the 1st time. In New Jersey samples, vitamin C and β-carotene were highest in the leaf blades versus whole leaf and petioles. Samples from Texas had highest amount of lutein, violaxanthin, and chlorophyll a and b in leaf blades versus whole leaf and petioles. Maximum DPPH free scavenging activity was found in MeOH: water: acid (80:19:1) and the combination of FA with EtOH: water: acid (80:19:1) demonstrated the higher level of total phenolic. Among six bile acids, sodium chenodeoxycholate was bound maximum in both Texas and New Jersey samples. This is the first report of anthocyanin identification from the midvein and petiole of Garnet Stem dandelion and results suggested that the phytochemicals and nutrients are highest in the leaf but may vary the amount depending on harvest location.. Four anthocyanins in the red midrib and petioles of Garnet Stem could be a potential source for antioxidants and can be used as a source of natural food color.

Topics: Anthocyanins; Antioxidants; Ascorbic Acid; beta Carotene; Bile Acids and Salts; Chenodeoxycholic Acid; Chlorophyll; Chlorophyll A; Glucosides; Lutein; New Jersey; Phytochemicals; Plant Leaves; Plant Stems; Taraxacum; Texas; 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

It is proposed that xanthophylls, and carotenoids in general, may assist in energy transfer from the chlorophyll Soret band to the Q band. Ground-state (1Ag ) and excited-state (1Bu ) optimizations of violaxanthin (Vx) and zeaxanthin (Zx) are performed in an environment mimicking the light-harvesting complex II (LHCII), including the closest chlorophyll b molecule (Chl). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) is used in combination with a semi-empirical description to obtain the excited-state geometries, supported by additional DFT/multireference configuration interaction calculations, with and without point charges representing LHCII. In the ground state, Vx and Zx show similar properties. At the 1Bu minimum, the energy of the Zx 1Bu state is below the Chl Q band, in contrast to Vx. Both Vx and Zx may act as acceptors of Soret-state energy; transfer to the Q band seems to be favored for Vx. These findings suggest that carotenoids may generally mediate Soret-to-Q energy flow in LHCII.

Topics: Carotenoids; Chlorophyll; Energy Transfer; Light-Harvesting Protein Complexes; Models, Molecular; Quantum Theory; Thermodynamics; Xanthophylls; Zeaxanthins

Collecting energy for photosystem II is facilitated by several pigments, xanthophylls and chlorophylls, embedded in the light harvesting complex II (LHCII). One xanthophyll, violaxanthin (Vio), is loosely bound at a site close to a chlorophyll b (Chl). No final answer has yet been found for the role of this specific xanthophyll. We study the electronic structure of Vio in the presence of Chl and under the influence of the LHCII environment, represented by a point charge field (PCF). We compare the capability of the long range corrected density functional theory (DFT) functional CAM-B3LYP to B3LYP for the modeling of the UV/vis spectrum of the Vio+Chl pair. CAM-B3LYP was reported to allow for a very realistic reproduction of bond length alternation of linear polyenes, which has considerable impact on the carotenoid structure and spectrum. To account for the influence of the LHCII environment, the chromophore geometries are optimized using an ONIOM(DFT/6-31G(d):PM6) scheme. Our calculations show that the energies of the locally excited states are almost unaffected by the presence of the partner chromophore or the PCF. There are, however, indications for excitonic coupling of the Chl Soret band and Vio. We propose that Vio may accept energy from blue-light excited Chl.

Topics: Chlorophyll; Electrons; Light-Harvesting Protein Complexes; Models, Molecular; Pisum sativum; Protein Conformation; Quantum Theory; Solutions; Xanthophylls

The effects of high Zn concentration were investigated in sugar beet (Beta vulgaris L.) plants grown in a controlled environment in hydroponics. High concentrations of Zn sulphate in the nutrient solution (50, 100 and 300 microm) decreased root and shoot fresh and dry mass, and increased root/shoot ratios, when compared to control conditions (1.2 microm Zn). Plants grown with excess Zn had inward-rolled leaf edges and a damaged and brownish root system, with short lateral roots. High Zn decreased N, Mg, K and Mn concentrations in all plant parts, whereas P and Ca concentrations increased, but only in shoots. Leaves of plants treated with 50 and 100 microm Zn developed symptoms of Fe deficiency, including decreases in Fe, chlorophyll and carotenoid concentrations, increases in carotenoid/chlorophyll and chlorophyll a/b ratios and de-epoxidation of violaxanthin cycle pigments. Plants grown with 300 microm Zn had decreased photosystem II efficiency and further growth decreases but did not have leaf Fe deficiency symptoms. Leaf Zn concentrations of plants grown with excess Zn were high but fairly constant (230-260 microg.g(-1) dry weight), whereas total Zn uptake per plant decreased markedly with high Zn supply. These data indicate that sugar beet could be a good model to investigate Zn homeostasis mechanisms in plants, but is not an efficient species for Zn phytoremediation.

Topics: Beta vulgaris; Biological Transport; Carbon Dioxide; Chlorophyll; Chlorophyll A; FMN Reductase; Hydroponics; Minerals; Nitrogen; Oxygen; Photosystem II Protein Complex; Plant Structures; Trace Elements; Xanthophylls; Zinc; Zinc Sulfate

Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). We found evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a delocalized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can "tune" the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophyll-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

Topics: Arabidopsis Proteins; Chlorophyll; Chlorophyll A; Chlorophyll Binding Proteins; Chloroplast Proteins; Electron Transport; Electrophysiology; Light; Light-Harvesting Protein Complexes; Lutein; Models, Molecular; Photosystem II Protein Complex; Protein Conformation; Recombinant Proteins; Ribonucleoproteins; Structure-Activity Relationship; Xanthophylls; Zeaxanthins

Three plant xanthophylls are components of the xanthophyll cycle in which, upon exposure of leaves to high light, the enzyme violaxanthin de-epoxidase (VDE) transforms violaxanthin into zeaxanthin via the intermediate antheraxanthin. Previous work () showed that xanthophylls are bound to Lhc proteins and that substitution of violaxanthin with zeaxanthin induces conformational changes and fluorescence quenching by thermal dissipation. We have analyzed the efficiency of different Lhc proteins to exchange violaxanthin with zeaxanthin both in vivo and in vitro. Light stress of Zea mays leaves activates VDE, and the newly formed zeaxanthin is found primarily in CP26 and CP24, whereas other Lhc proteins show a lower exchange capacity. The de-epoxidation system has been reconstituted in vitro by using recombinant Lhc proteins, recombinant VDE, and monogalactosyl diacylglycerol (MGDG) to determine the intrinsic capacity for violaxanthin-to-zeaxanthin exchange of individual Lhc gene products. Again, CP26 was the most efficient in xanthophyll exchange. Biochemical and spectroscopic analysis of individual Lhc proteins after de-epoxidation in vitro showed that xanthophyll exchange occurs at the L2-binding site. Xanthophyll exchange depends on low pH, implying that access to the binding site is controlled by a conformational change via lumenal pH. These findings suggest that the xanthophyll cycle participates in a signal transduction system acting in the modulation of light harvesting versus thermal dissipation in the antenna system of higher plants.

Topics: beta Carotene; Chlorophyll; Chlorophyll A; Epoxide Hydrolases; Glycerides; Light; Light-Harvesting Protein Complexes; Oxidation-Reduction; Photosynthetic Reaction Center Complex Proteins; Plant Leaves; Plastids; Spectrophotometry; Xanthophylls; Zea mays

Under high-light conditions, photoprotective mechanisms minimize the damaging effects of excess light. A primary photoprotective mechanism is thermal dissipation of excess excitation energy within the light-harvesting complex of photosystem II (LHCII). Although roles for both carotenoids and specific polypeptides in thermal dissipation have been reported, neither the site nor the mechanism of this process has been defined precisely. Here, we describe the physiological and molecular characteristics of the Chlamydomonas reinhardtii npq5 mutant, a strain that exhibits little thermal dissipation. This strain is normal for state transition, high light-induced violaxanthin deepoxidation, and low light growth, but it is more sensitive to photoinhibition than the wild type. Furthermore, both pigment data and measurements of photosynthesis suggest that the photosystem II antenna in the npq5 mutant has one-third fewer light-harvesting trimers than do wild-type cells. The npq5 mutant is null for a gene designated Lhcbm1, which encodes a light-harvesting polypeptide present in the trimers of the photosystem II antennae. Based on sequence data, the Lhcbm1 gene is 1 of 10 genes that encode the major LHCII polypeptides in Chlamydomonas. Amino acid alignments demonstrate that these predicted polypeptides display a high degree of sequence identity but maintain specific differences in their N-terminal regions. Both physiological and molecular characterization of the npq5 mutant suggest that most thermal dissipation within LHCII of Chlamydomonas is dependent on the peripherally associated trimeric LHC polypeptides.

Topics: Algal Proteins; Amino Acid Sequence; Animals; beta Carotene; Carotenoids; Chlamydomonas; Chlorophyll; Chlorophyll A; Fluorescence; Light; Light-Harvesting Protein Complexes; Molecular Sequence Data; Mutation; Organisms, Genetically Modified; Oxygen; Photosynthesis; Photosynthetic Reaction Center Complex Proteins; Photosystem II Protein Complex; Pigments, Biological; Sequence Alignment; Sequence Homology, Amino Acid; Temperature; Xanthophylls

Guard cells of the orchid genus, Paphiopedilum have been reported to lack developed chloroplasts and detectable chlorophyll a autofluorescence. Paphiopedilum stomata lack a photosynthesis-dependent opening response but have a blue light-specific opening. The present study found that low fluence rate green and red light elicited stomatal opening in Paphiopedilum and this opening was reversed by far red light, indicating the presence of a phytochrome-mediated opening response. Phytochrome-dependent, red light-stimulated opening was largest under low fluence rates and decreased to near zero as fluence rate increased. A recently discovered green light reversibility of blue light-specific stomatal opening was used to probe the properties of the blue light response in Paphiopedilum stomata. Blue light-stimulated opening was completely reversed by green light in the presence of far red light. Red light enhanced the blue light response of Paphiopedilum guard cells when given as a pretreatment or together with blue light. Analysis of guard cell pigments showed that guard cells have small amounts of chlorophyll a and b, zeaxanthin, violaxanthin, antheraxanthin and lutein. Zeaxanthin content increased in response to blue light or ascorbate and declined in the dark or under illumination in the presence of dithiothreitol, indicating the presence of an active xanthophyll cycle. Thus Paphiopedilum stomata possess both a blue light-mediated opening response with characteristics similar to species with normal chloroplast development and a novel phytochrome-mediated opening response.

Topics: Adaptation, Physiological; Ascorbic Acid; beta Carotene; Chlorophyll; Chlorophyll A; Dithiothreitol; Light; Lutein; Orchidaceae; Photosynthesis; Phytochrome; Pigments, Biological; Plant Epidermis; Xanthophylls; Zeaxanthins

Light-harvesting complexes (LHC) of higher plants are composed of at least 10 different proteins. Despite their pronounced amino acid sequence homology, the LHC of photosystem II show differences in pigment binding that are interpreted in terms of partly different functions. By contrast, there is only scarce knowledge about the pigment composition of LHC of photosystem I, and consequently no concept of potentially different functions of the various LHCI exists. For better insight into this issue, we isolated native LHCI-730 and LHCI-680. Pigment analyses revealed that LHCI-730 binds more chlorophyll and violaxanthin than LHCI-680. For the first time all LHCI complexes are now available in their recombinant form; their analysis allowed further dissection of pigment binding by individual LHCI proteins and analysis of pigment requirements for LHCI formation. By these different approaches a correlation between the requirement of a single chlorophyll species for LHC formation and the chlorophyll a/b ratio of LHCs could be detected, and indications regarding occupation of carotenoid-binding sites were obtained. Additionally the reconstitution approach allowed assignment of spectral features observed in native LHCI-680 to its components Lhca2 and Lhca3. It is suggested that excitation energy migrates from chlorophyll(s) fluorescing at 680 (Lhca3) via those fluorescing at 686/702 nm (Lhca2) or 720 nm (Lhca3) to the photosystem I core chlorophylls.

Topics: beta Carotene; Binding Sites; Chlorophyll; Chlorophyll A; Light-Harvesting Protein Complexes; Photosynthetic Reaction Center Complex Proteins; Photosystem I Protein Complex; Photosystem II Protein Complex; Pigments, Biological; Plant Leaves; Solanum lycopersicum; Spectrometry, Fluorescence; Xanthophylls

The steady state absorption and fluorescence spectroscopic properties of the xanthophylls, violaxanthin, zeaxanthin, and lutein, and the efficiencies of singlet energy transfer from the individual xanthophylls to chlorophyll have been investigated in recombinant CP26 protein overexpressed in Escherichia coli and then refolded in vitro with purified pigments. Also, the effect of the different xanthophylls on the extents of static and dynamic quenching of chlorophyll fluorescence has been investigated. Absorption, fluorescence, and fluorescence excitation demonstrate that the efficiency of light harvesting from the xanthophylls to chlorophyll a is relatively high and insensitive to the particular xanthophyll that is present. A small effect of the different xanthophylls is observed on the extent of quenching of Chl fluorescence. The data provide the precise wavelengths of the absorption and fluorescence features of the bound pigments in the highly congested spectral profiles from these light-harvesting complexes. This information is important in assessing the mechanisms by which higher plants dissipate excess energy in light-harvesting proteins.

Topics: beta Carotene; Chlorophyll; Chlorophyll A; Energy Transfer; Escherichia coli; Light-Harvesting Protein Complexes; Lutein; Photochemistry; Photosynthetic Reaction Center Complex Proteins; Photosystem II Protein Complex; Pigments, Biological; Recombinant Proteins; Spectrometry, Fluorescence; Spinacia oleracea; Xanthophylls; Zeaxanthins

Excess light energy absorbed by the chloroplast membranes of green plants is dissipated by nonradiative de-excitation in order to protect against photodamage. This is observed as the nonphotochemical quenching of chlorophyll fluorescence, which has been suggested to result from an alteration in the structure and function of the chlorophyll a/b light-harvesting complexes of photosystem II (LHCII) due to the combined effects of protonation and the de-epoxidation of bound violaxanthin to form zeaxanthin. In agreement with this hypothesis, it is shown that the light-harvesting chlorophyll a/b proteins purified from spinach leaves exhibit pH-stimulated quenching of chlorophyll fluorescence; this quenching shares all the key features observed for the nonphotochemical quenching of chlorophyll fluorescence in vivo. In the case of the two minor complexes, LHCIIa (CP29) and LHCIIc (CP26), quenching is much greater than in the bulk complex LHCIIb and is strongly inhibited by the reagent dicyclohexylcarbodiimide. The carotenoids violaxanthin and zeaxanthin cause strong inhibition and stimulation of quenching, respectively, in these complexes. The results of this study are consistent with the suggestion that the minor light-harvesting complexes play a crucial role in photoprotective energy dissipation in the photosynthetic membrane of green plants. Moreover, for the first time, a system using isolated LHCIIa and LHCIIc for the study of the regulation of light harvesting is described.

Topics: beta Carotene; Carotenoids; Carrier Proteins; Chlorophyll; Chlorophyll A; Fluorescence; Light-Harvesting Protein Complexes; Photosynthesis; Photosynthetic Reaction Center Complex Proteins; Photosystem II Protein Complex; Plants; Xanthophylls