Flood projections within the Niger River Basin under future land use and climate change.

This study assesses future flood risk in the Niger River Basin (NRB), for the first time considering the simultaneous effects of both projected climate change and land use changes. For this purpose, an ecohydrological process-based model (SWIM) was set up and validated for past climate and land use dynamics of the entire NRB. Model runs for future flood risks were conducted with an ensemble of 18 climate models, 13 of them dynamically downscaled from the CORDEX Africa project and five statistically downscaled Earth System Models. Two climate and two land use change scenarios were used to cover a broad range of potential developments in the region. Two flood indicators (annual 90th percentile and the 20-year return flood) were used to assess the future flood risk for the Upper, Middle and Lower Niger as well as the Benue. The modeling results generally show increases of flood magnitudes when comparing a scenario period in the near future (2021-2050) with a base period (1976-2005). Land use effects are more uncertain, but trends and relative changes for the different catchments of the NRB seem robust. The dry areas of the Sahelian and Sudanian regions of the basin show a particularly high sensitivity to climatic and land use changes, with an alarming increase of flood magnitudes in parts. A scenario with continuing transformation of natural vegetation into agricultural land and urbanization intensifies the flood risk in all parts of the NRB, while a "regreening" scenario can reduce flood magnitudes to some extent. Yet, land use change effects were smaller when compared to the effects of climate change. In the face of an already existing adaptation deficit to catastrophic flooding in the region, the authors argue for a mix of adaptation and mitigation efforts in order to reduce the flood risk in the NRB.

Proteomic and genomic modulations induced by γ-irradiation of human blood lymphocytes.

PURPOSE: Quantitative evaluation of early response proteins (ERPRO) and early response genes (ERG) following γ-irradiation of human lymphocytes; identification of specific proteins and genes as candidate biomarkers for the development of a novel biodosimeter. MATERIALS AND METHODS: Human peripheral blood lymphocytes were exposed to clinically relevant doses (1, 2 and 4 Gy) of γ-radiation ex-vivo. Analyses of protein and gene expression modulation were conducted 2 h post-irradiation. Global modulations were monitored using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and DNA microarray analyses of the samples originating from one human donor. On the proteome level, both phosphorylated and non-phosphorylated proteins were considered. Proteins and genes of specific interest were further targeted using Western blot (WB) and real-time quantitative polymerase chain reaction (RT-qPCR) techniques, employing samples from several human donors (n=3). RESULTS: A set of ERPRO and ERG showing significant alterations 2 h post-γ-irradiation have been identified in human lymphocytes. The most radiation responsive genes and proteins indicated alterations of cellular structure (ß-actin, talin-1 [TLN1], talin-2, zyxin-2), immune and defence reactions (major histocompatibility complex binding protein-2 [MBP2], interleukin-17E and interferon-γ), cell cycle control (cyclin-dependent kinase inhibitor-1A [CDKN1A], mouse double minute-2, annexin-A6 [ANXA6], growth arrest and DNA-damage-inducible protein-α [GADD45A], proliferating cell nuclear antigen [PCNA], dual specificity phosphatase-2 and 8 [DUSP8]) as well as detoxification processes (peroxin-1) and apoptosis (B-cell lymphoma-2 binding component-3 [BBC3]). SUMMARY: The estimations of protein concentration modulation of TLN1 and CDKN1A, phosphorylation status of ANXA6 (dose range 0-2 Gy) and MBP2 as well as the alterations in the level of gene expressions of BBC3, DUSP8, GADD45A and PCNA appears to be of potential value for future biodosimetric applications.

Simplified automated image analysis for detection and phenotyping of Mycobacterium tuberculosis on porous supports by monitoring growing microcolonies.

BACKGROUND: Even with the advent of nucleic acid (NA) amplification technologies the culture of mycobacteria for diagnostic and other applications remains of critical importance. Notably microscopic observed drug susceptibility testing (MODS), as opposed to traditional culture on solid media or automated liquid culture, has shown potential to both speed up and increase the provision of mycobacterial culture in high burden settings. METHODS: Here we explore the growth of Mycobacterial tuberculosis microcolonies, imaged by automated digital microscopy, cultured on a porous aluminium oxide (PAO) supports. Repeated imaging during colony growth greatly simplifies "computer vision" and presumptive identification of microcolonies was achieved here using existing publically available algorithms. Our system thus allows the growth of individual microcolonies to be monitored and critically, also to change the media during the growth phase without disrupting the microcolonies. Transfer of identified microcolonies onto selective media allowed us, within 1-2 bacterial generations, to rapidly detect the drug susceptibility of individual microcolonies, eliminating the need for time consuming subculturing or the inoculation of multiple parallel cultures. SIGNIFICANCE: Monitoring the phenotype of individual microcolonies as they grow has immense potential for research, screening, and ultimately M. tuberculosis diagnostic applications. The method described is particularly appealing with respect to speed and automation.

Effect of (211)At alpha-particle irradiation on expression of selected radiation responsive genes in human lymphocytes.

PURPOSE: Analysis of the relative expression of radiation responsive genes (previously shown to respond to gamma-radiations) after exposure of human lymphocytes to (211)At alpha-particles and the suitability of these genes as potential markers for alpha-biodosimetry. MATERIALS AND METHODS: Lymphocytes isolated from the peripheral blood of two healthy human donors were exposed in triplicate for 30 min to different concentrations of Na(211)At at 37 degrees C (absorbed doses: 0.05-1.6 Gy). Following an incubation period (2 h), the total RNA was isolated from the irradiated lymphocytes and the relative expression of the following 18 genes was tested for change using TaqMan probes based upon the real-time quantitative polymerase chain reaction. METHOD: BBC3 (B-cell lymphoma 2 binding component 3), CD69 (cluster of differentiation 69), CDKN1A (cyclin-dependent kinase inhibitor 1A), DUSP8 (dual specificity phosphatase 8) EGR1 (early growth response 1), EGR4 (early growth response 4), GADD45A (growth arrest and DNA-damage-inducible, alpha), GRAP (growth factor receptor-bound protein 2-related adaptor protein), LAP1B (TOR1AIP1; torsin A interacting protein 1), IFNG (interferon gamma), ISG20L1 (interferon-stimulated exonuclease gene 20kDa - like 1), c-JUN (jun oncogene), MDM2 (mouse double minute 2), PCNA (proliferating cell nuclear antigen), PLK2 (polo-like kinase 2), RND1 (rho family GTPase 1), TNFSF9 (tumour necrosis factor superfamily member 9) and TRAF4 (tumour necrosis factor receptor-associated factor 4). RESULTS: The expressions of the 18 genes, except GRAP, were up-regulated following exposure to alpha-radiation. A comparison of the results of two individuals tested here showed great variability. Dependence of gene expression upon alpha-dose was observed in certain dose intervals for BBC3 (R(2) = 0.61 [individual 1] / 0.81 [individual 2], significance 0.2-1.6 Gy [1] / 0.05-0.1 Gy [2]) and MDM2 (R(2) = 0.78/0.54; 0.8-1.6 Gy [1], 0.05-0.1 Gy [2]) genes in both individuals. Additionally, for individual 1 the dose dependence was found for the following genes: ISG20L1 (R(2) = 0.69, 0.05-0.1 Gy), PCNA (R(2) = 0.59, 0.8-1.6 Gy) and IFNG (R(2) = 0.74 up to 0.4 Gy, 0.05-0.1 Gy). CONCLUSION: Candidate genes for a possible role in future early-phase (2 h) alpha-biodosimetry are BBC3, ISG20L1, MDM2, PCNA and IFNG.

Two stereoisomers of spheroidene in the Rhodobacter sphaeroides R26 reaction center: a DFT analysis of resonance Raman spectra.

From a theoretical analysis of the resonance Raman spectra of 19 isotopomers of spheroidene reconstituted into the reaction center (RC) of Rhodobacter sphaeroides R26, we conclude that the carotenoid in the RC occurs in two configurations. The normal mode underlying the resonance Raman transition at 1239 cm(-1), characteristic for spheroidene in the RC, has been identified and found to uniquely refer to the cis nature of the 15,15' carbon-carbon double bond. Detailed analysis of the isotope-induced shifts of transitions in the 1500-1550 cm(-1) region proves that, besides the 15,15'-cis configuration, spheroidene in the RC adopts another cis-configuration, most likely the 13,14-cis configuration.

Negative correlation between poly-ADP-ribosylation of spleen cell histone proteins and initial duration of dimethylnitrosamine exposure to mice in vivo measured by Western blot immunoprobe assay: a possible biomarker for cancer detection.

Improved cancer detection involving suitable biomarkers with easy applicability is a challenge to our fight against cancer. Poly-ADP-ribosylation (PAR) of proteins is a likely candidate biomarker for this purpose because it meets the criterion well. This report is a step towards testing suitability of PAR as a biomarker for cancer detection. Swiss albino mice were exposed to hepatocarcinogen, dimethylnitrosamine (DMN), at a chronic dose, which is known to induce carcinogenesis in liver. PAR was monitored by a Western blot immunoprobe assay in spleen, a lymphoid organ, to find a correlation between PAR of spleen histone proteins and duration of DMN exposure. A negative, non-linear correlation was found for most histone proteins. The inhibition of PAR of histones was significant from 4 weeks onwards until the end of the observation. The inhibition was potentiated when 3-aminobenzamide was simultaneously administered. The results open up the possibility of PAR of cellular proteins being used as biomarker for cancer detection.

Transport of cis- and trans-4-[(18)F]fluoro-L-proline in F98 glioma cells.

The transport mechanisms of cis-4-[(18)F]fluoro-L-proline (cis-FPro) and trans-4-[(18)F]fluoro-L-proline (trans-FPro) were studied in F98 rat glioma cells in comparison to the natural parent [(3)H]-L-proline. Uptake rates of cis-FPro and trans-FPro in F98 glioma cells were 50-70% lower than those of [(3)H]-L-proline. The amino transport system A inhibitor MeAIB reduced the uptake of [(3)H]-L-proline by 30% and uptake of cis-FPro by 46% while uptake of trans-FPro was not significantly changed. BCH inhibited the uptake of all tracers by 35-44%, serine by 70-90% and L-proline by 60 -80%. Absence of Na(+) reduced uptake of all tracers significantly but no further inhibitory effect could be observed which suggests a component of unspecific uptake. Radioactivity of cis- and trans-FPro in the acid precipitable fraction was < 1% after 120 min incubation time while [(3)H]-L-proline exhibited a 20% incorporation into protein. Whole body PET scans in humans demonstrated a retention of cis-FPro in the renal cortex, liver and the pancreas while trans-FPro was retained particularly in muscles. We conclude that system A amino acid transport appears to be selectively relevant for cis-FPro which may contribute to the observed differences in whole body distribution of cis-FPro and trans-FPro in humans.

Electrochemical reactions of redox cofactors in Rhodobacter sphaeroides reaction center proteins in lipid films.

Cyclic voltammetry of thin films made from the lipid dimyristoylphosphatidyl choline and reaction centers from the purple bacterium Rhodobacter sphaeroides on pyrolytic graphite electrodes in bromide-free pH 8 buffers at 4 degrees C revealed an oxidation peak at 0.98 V and a reduction peak at -0.17 V vs. NHE. No reverse CV peaks were found, suggesting chemical irreversibility. The reduction peak disappeared for reaction centers depleted of quinones, suggesting that the peak represents reduction of this cofactor. The oxidation peak showed a catalytic current increase in the presence of small amounts of ferrous cytochrome c, and decreased by 85% when illuminated by visible light, suggesting assignment to the primary donor (P) cofactor. While oxidized primary donor P(+) is destroyed upon electrochemical formation in the film, reaction of ferrous cyt c with P(+) suggests its persistence in the films on the microsecond time scale.

Influence of bromide on electrochemistry of photosynthetic reaction center films on gold electrodes.

A strong influence of bromide ion was found on voltammetry of layered films of photosynthetic reaction center (RC) protein and polyions on gold electrodes. Similar, but not identical, cyclic voltammetry peaks were observed for polyion films on gold with and without RC when the buffer solutions contained bromide ion. CVs of RC films were quite different in the absence of bromide. These new findings suggest that previously published results were biased by significant background peaks involving bromide ion adsorption/desorption.

Spectroscopic studies of the low-lying singlet excited electronic states and photochemical properties of carotenoids.

Investigations of the singlet excited state properties of carotenoids using steady-state fluorescence, transient absorption pump-probe, two-photon excitation, and resonance Raman excitation spectroscopies are described. The application of these experimental techniques to the specific problem of determining the S1 excited energies of carotenoids is discussed in detail, and the recent literature pertaining to the assignment of charge transfer states in carotenoids and states described as having particular pseudoparity elements is reviewed. Hypothetical schemes for how these states may account for some of the dynamic and photochemical behavior of carotenoids are presented.

Carotenoid photooxidation in photosystem II.

Carotenoids are known to function as light-harvesting pigments and they play important roles in photoprotection in both plant and bacterial photosynthesis. These functions are also important for carotenoids in photosystem II. In addition, beta-carotene recently has been found to function as a redox intermediate in an alternate pathway of electron transfer within photosystem II. This redox role of a carotenoid in photosystem II is unique among photosynthetic reaction centers and stems from the very highly oxidizing intermediates that form in the process of water oxidation. In this minireview, an overview of the electron-transfer reactions in photosystem II is presented, with an emphasis on those involving carotenoids. The carotenoid composition of photosystem II and the physical methods used to study the structure of the redox-active carotenoid are reviewed. Possible roles of carotenoid cations in photoprotection of photosystem II are discussed.

Photochemical behavior of xanthophylls in the recombinant photosystem II antenna complex, CP26.

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.

The inter-rater reliability of estimating the size of burns from various burn area chart drawings.

The accuracy and variability of burn size calculations using four Lund and Browder charts currently in clinical use and two Rule of Nine's diagrams were evaluated. The study showed that variability in estimation increased with burn size initially, plateaued in large burns and then decreased slightly in extensive burns. The Rule of Nine's technique often overestimates the burn size and is more variable, but can be performed somewhat faster than the Lund and Browder method. More burn experience leads to less variability in burn area chart drawing estimates. Irregularly shaped burns and burns on the trunk and thighs had greater variability than less irregularly shaped burns or burns on more defined anatomical parts of the body.

Mechanism of nonphotochemical quenching in green plants: energies of the lowest excited singlet states of violaxanthin and zeaxanthin.

The xanthophyll cycle is an enzymatic, reversible process through which the carotenoids violaxanthin, antheraxanthin, and zeaxanthin are interconverted in response to the need to balance light absorption with the capacity to use the energy to drive the reactions of photosynthesis. The cycle is thought to be one of the main avenues for safely dissipating excitation energy absorbed by plants in excess of that needed for photosynthesis. One of the key factors needed to elucidate the molecular mechanism by which the potentially damaging excess energy is dissipated is the energy of the lowest excited singlet (S(1)) state of the xanthophyll pigments. Absorption from the ground state (S(0)) to S(1) is forbidden by symmetry, making a determination of the S(1) state energies of these molecules by absorption spectroscopy very difficult. Fluorescence spectroscopy is potentially the most direct method for obtaining the S(1) state energies. However, because of problems with sample purity, low emission quantum yields, and detection sensitivity, fluorescence spectra from these molecules, until now, have never been reported. In this work these technical obstacles have been overcome, and S(1) --> S(0) fluorescence spectra of violaxanthin and zeaxanthin are presented. The energies of the S(1) states deduced from the fluorescence spectra are 14 880 +/- 90 cm(-)(1) for violaxanthin and 14 550 +/- 90 cm(-)(1) for zeaxanthin. The results provide important insights into the mechanism of nonphotochemical dissipation of excess energy in plants.

Fast reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film.

Direct reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film was observed in this work. The redox potential E0' = 0.46 V vs. NHE for first primary donor redox couple P/P+ was accurately measured from reversible CV or SWV peaks, which were quite close to those obtained from optic redox titration method. Reaction center (RC) in film was found re-constituted in such an ordered way that the orientation of RC favored the electron transfer in film. Thus, the protein electroactivity seems to be turned on in this artificial biomimic thin film. Furthermore, RC in the film features a photo-induced redox-peak fluctuation, suggesting an intact and functional state for RC in such film. Redox peaks were also found dependent of pH, implying a proton-coupled electron transfer occurring in film. Charge recombination was observed accompanied with change of electrochemical driving force. Electrochemical model assuming several classes of electroactive sites in the films on the electrode with a dispersion of standard potentials successfully fits SWV experimental data at different pulse height and frequency.

Protein modifications affecting triplet energy transfer in bacterial photosynthetic reaction centers.

The efficiency of triplet energy transfer from the special pair (P) to the carotenoid (C) in photosynthetic reaction centers (RCs) from a large family of mutant strains has been investigated. The mutants carry substitutions at positions L181 and/or M208 near chlorophyll-based cofactors on the inactive and active sides of the complex, respectively. Light-modulated electron paramagnetic resonance at 10 K, where triplet energy transfer is thermally prohibited, reveals that the mutations do not perturb the electronic distribution of P. At temperatures > or = 70 K, we observe reduced signals from the carotenoid in most of the RCs with L181 substitutions. In particular, triplet transfer efficiency is reduced in all RCs in which a lysine at L181 donates a sixth ligand to the monomeric bacteriochlorophyll B(B). Replacement of the native Tyr at M208 on the active side of the complex with several polar residues increased transfer efficiency. The difference in the efficiencies of transfer in the RCs demonstrates the ability of the protein environment to influence the electronic overlap of the chromophores and thus the thermal barrier for triplet energy transfer.

Triplet energy transfer between the primary donor and carotenoids in Rhodobacter sphaeroides R-26.1 reaction centers incorporated with spheroidene analogs having different extents of pi-electron conjugation.

Three carotenoids, spheroidene, 3,4-dihydrospheroidene and 3,4,5,6-tetrahydrospheroidene, having 8, 9 and 10 conjugated carbon-carbon double bonds, respectively, were incorporated into Rhodobacter (Rb.) sphaeroides R-26.1 reaction centers. The extents of binding were found to be 95 +/- 5% for spheroidene, 65 +/- 5% for 3,4-dihydrospheroidene and 60 +/- 10% for 3,4,5,6-tetrahydrospheroidene. The dynamics of the triplet states of the primary donor and carotenoid were measured at room temperature by flash absorption spectroscopy. The carotenoid, spheroidene, was observed to quench the primary donor triplet state. The triplet state of spheroidene that was formed subsequently decayed to the ground state with a lifetime of 7.0 +/- 0.5 microseconds. The primary donor triplet lifetime in the Rb. sphaeroides R-26.1 reaction centers lacking carotenoids was 60 +/- 5 microseconds. Quenching of the primary donor triplet state by the carotenoid was not observed in the Rb. sphaeroides R-26.1 reaction centers containing 3,4-dihydrospheroidene nor in the R-26.1 reaction centers containing 3,4,5,6-tetrahydrospheroidene. Triplet-state electron paramagnetic resonance was also carried out on the samples. The experiments revealed carotenoid triple-state signals in the Rb. sphaeroides R-26.1 reaction centers incorporated with spheroidene, indicating that the primary donor triplet is quenched by the carotenoid. No carotenoid signals were observed from Rb. sphaeroides R-26.1 reaction centers incorporating 3,4-dihydrospheroidene nor in reaction centers incorporating 3,4,5,6-tetrahydrospheroidene. Circular dichroism, steady-state absorbance band shifts accompanying the primary photochemistry in the reaction center and singlet energy transfer from the carotenoid to the primary donor confirm that the carotenoids are bound in the reaction centers and interacting with the primary donor. These studies provide a systematic approach to exploring the effects of carotenoid structure and excited-state energy on triplet transfer between the primary donor and carotenoids in reaction centers from photosynthetic bacteria.

Analysis of magnetization transfer effects on T1-weighted spin-echo scans using a simple tissue phantom simulating gadolinium-enhanced brain lesions.

The purpose of this study was to analyze the effect of several magnetization transfer (MT) pulse and T1-weighted spin-echo (SE) sequence parameters on lesion-to-background contrast, using a simple tissue phantom emulating the T1 relaxation and MT properties of gadolinium-enhanced brain lesions. Eggbeaters (Nabisco Inc., East Hanover, NJ) liquid egg product was doped with gadolinium in six concentrations from .0 to 1.0 mmol and cooked. The gadolinium-doped egg phantom and normal volunteer brains were studied using an SE sequence with TE = 20 msec and high power, pulsed, off-resonance MT saturation. The effects of MT pulse frequency offset (1,000-6,000 Hz), sequence repetition time (TR = 500-1,000 msec, with MT power held constant), and slice-select flip angle (60-120 degrees) on the magnetization transfer ratio (MTR) and the simulated lesion-to-background contrast were determined at the different "intralesion" gadolinium concentrations. The MTR and lesion-to-background contrast of all materials were greatest at narrow MT pulse frequency offsets. There was in inverse relationship between gadolinium concentration and MTR and a positive correlation between the gadolinium concentration and lesion-to-background (L/B) contrast, a weak negative correlation between slice-select flip angle and L/B, and a negative correlation between TR and L/B. The relaxation properties and MT behavior of the egg phantom are close to that expected for enhancing brain lesions, allowing a rigorous analysis of several variables affecting lesion-to-background contrast for high MT power, T1-weighted SE sequences.

Resonance Raman spectroscopy of 2H-labelled spheroidenes in petroleum ether and in the Rhodobacter sphaeroides reaction centre.

As a step towards the structural analysis of the carotenoid spheroidene in the Rhodobacter sphaeroides reaction centre, we present the resonance Raman spectra of 14-2H, 15-2H, 15'-2H, 14'-2H, 14,15'-2H2 and 15-15'-2H2 spheroidenes in petroleum ether and, except for 14,15'-2H2 spheroidene, in the Rb. sphaeroides R26 reaction center (RC). Analysis of the spectral changes upon isotopic substitution allows a qualitative assignment of most of the vibrational bands to be made. For the all-trans spheroidenes in solution the resonance enhancement of the Raman bands is determined by the participation of carbon carbon stretching modes in the centre of the conjugated chain, the C9 to C15' region. For the RC-bound 15,15'-cis spheroidenes, enhancement is determined by the participation of carbon-carbon stretching modes in the centre of the molecule, the C13 to C13' region. Comparison of the spectra in solution and in the RC reveals evidence for an out-of-plane distortion of the RC-bound spheroidene in the central C14 to C14' region of the carotenoid. The characteristic 1240 cm-1 band in the spectrum of the RC-bound spheroidene has been assigned to a normal mode that contains the coupled C12-C13 and C13'-C12' stretch vibrations.

The lifetimes and energies of the first excited singlet states of diadinoxanthin and diatoxanthin: the role of these molecules in excess energy dissipation in algae.

The lifetimes of the first excited singlet states (2(1)A(g)) of diadinoxanthin and diatoxanthin, carotenoids involved in the xanthophyll cycle in some genera of algae, have been measured by femtosecond time-resolved optical spectroscopy to be 22.8 +/- 0.1 ps and 13.3 +/- 0.1 ps, respectively. Using the energy gap law for radiationless transitions set forth by Englman and Jortner (Mol. Phys. 18 (1970) 145-164), these lifetimes correspond to S1 excited state energies of 15210 cm-1 for diadinoxanthin and 14620 cm-1 for diatoxanthin. The lowest excited singlet state energy of Chl a has an energy of 14700 cm-1. The fact that the S1 state energy of diadinoxanthin lies above that of Chl a, whereas the S1 state energy of diatoxanthin lies below that of Chl a, suggests that the xanthophyll cycle involving the enzymatic interconversion of diadinoxanthin and diatoxanthin may play a role in regulating energy flow between these molecules and Chl a in many species of algae, essentially fulfilling a role identical to that proposed for violaxanthin and zeaxanthin in higher plants and green algae (Frank et al. (1994) Photosyn. Res. 41, 389-395).