Pigment Ratios Research Articles

Effects of iron availability on pigment signature and biogenic silica production in the coastal diatomChaetoceros gracilis

The effects of iron availability on pigment signature and biogenic silica production were investigated for the first time in the coastal diatom Chaetoceros gracilis (isolated from the SW coast of the Bay of Bengal, India). Results revealed that increase in iron supply considerably increases chlorophyll a based specific growth rates, whereas, it decreases the values of diatoxanthin index and photoprotective to light harvesting pigment ratios. It is likely that, under iron stress C. gracilis activated a strong photoprotection mechanism by maximising the conversion of diadinoxanthin to diatoxanthin and by increasing overall amount of photoprotective pigments relative to light harvesting pigments. The xanthophyll cycle comprising of diadinoxanthin and diatoxanthin seems to be the principal photoprotective mechanism in C. gracilis and is consistent with some earlier studies. It is suggested that under iron limited conditions the diatoxanthin index and the ratio of photoprotective to light harvesting pigments can be used as physiological markers for iron stress in C. gracilis. The ratios of biogenic silica to chlorophyll a were considerably decreased with increasing iron supply indicating the possibility of reduced cellular silica content under iron enriched conditions; however, supplementary information is required to confirm this observation.

Enhanced production of pigments by addition of surfactants in submerged fermentation of Monascus purpureus H1102

The production of pigments by Monascus spp. has attracted increasing attention. Modification of the cell membrane structure by addition of surfactants has proved to be effective for the secretion of intracellular metabolites. Hence in this study the effects and underlying mechanism of surfactants on the production of pigments in submerged fermentation of Monascus purpureus H1102 were systematically investigated. Various surfactants exerted significant but different impacts on the biomass and production of pigments. The maximum production of pigment (304.3 U mL(-1) ) and highest extracellular/intracellular pigment ratio (1.46) were achieved when 15 g L(-1) Triton X-100 was added at 24 h of fermentation, corresponding to significant increases of 88.4 and 240% respectively compared with the control. Meanwhile, the concentration of citrinin (0.94 mg L(-1) ) was 20.6% lower than that of the control. A further study on the fatty acid composition of M. purpureus H1102 showed that the unsaturated/saturated fatty acid ratio and the index of unsaturated fatty acid increased significantly with the addition of Triton X-100. The addition of surfactant Triton X-100 could greatly enhance the production of pigment. It was suggested that Triton X-100 facilitated the secretion of intracellular pigment and therefore enhanced pigment production accordingly.

Effects of iron availability on pigment signature and biogenic silica production in the coastal diatom Chaetoceros gracilis

The effects of iron availability on pigment signature and biogenic silica production were investigated for the first time in the coastal diatom Chaetoceros gracilis (isolated from the SW coast of the Bay of Bengal, India). Results revealed that increase in iron supply considerably increases chlorophyll a based specific growth rates, whereas, it decreases the values of diatoxanthin index and photoprotective to light harvesting pigment ratios. It is likely that, under iron stress C. gracilis activated a strong photoprotection mechanism by maximising the conversion of diadinoxanthin to diatoxanthin and by increasing overall amount of photoprotective pigments relative to light harvesting pigments. The xanthophyll cycle comprising of diadinoxanthin and diatoxanthin seems to be the principal photoprotective mechanism in C. gracilis and is consistent with some earlier studies. It is suggested that under iron limited conditions the diatoxanthin index and the ratio of photoprotective to light harvesting pigments can be used as physiological markers for iron stress in C. gracilis. The ratios of biogenic silica to chlorophyll a were considerably decreased with increasing iron supply indicating the possibility of reduced cellular silica content under iron enriched conditions; however, supplementary information is required to confirm this observation.

Chlorophyll fluorescence kinetics, photosynthetic activity, and pigment composition of blue-shade and half-shade leaves as compared to sun and shade leaves of different trees

The chlorophyll (Chl) fluorescence induction kinetics, net photosynthetic CO2 fixation rates P N, and composition of photosynthetic pigments of differently light exposed leaves of several trees were comparatively measured to determine the differences in photosynthetic activity and pigment adaptation of leaves. The functional measurements were carried out with sun, half-shade and shade leaves of seven different trees species. These were: Acer platanoides L., Ginkgo biloba L., Fagus sylvatica L., Platanus x acerifolia Willd., Populus nigra L., Quercus robur L., Tilia cordata Mill. In three cases (beech, ginkgo, and oak), we compared the Chl fluorescence kinetics and photosynthetic rates of blue-shade leaves of the north tree crown receiving only blue sky light but no direct sunlight with that of sun leaves. In these cases, we also determined in detail the pigment composition of all four leaf types. In addition, we determined the quantum irradiance and spectral irradiance of direct sunlight, blue skylight as well as the irradiance in half shade and full shade. The results indicate that sun leaves possess significantly higher mean values for the net CO2 fixation rates P N (7.8-10.7μmol CO2m(-2)s(-1) leaf area) and the Chl fluorescence ratio R Fd (3.85-4.46) as compared to shade leaves (mean P N of 2.6-3.8μmol CO2m(-2)s(-1) leaf area.; mean R Fd of 1.94-2.56). Sun leaves also exhibit higher mean values for the pigment ratio Chl a/b (3.14-3.31) and considerably lower values for the weight ratio total chlorophylls to total carotenoids, (a+b)/(x+c), (4.07-4.25) as compared to shade leaves (Chl a/b 2.62-2.72) and (a+b)/(x+c) of 5.18-5.54. Blue-shade and half-shade leaves have an intermediate position between sun and shade leaves in all investigated parameters including the ratio F v/F o (maximum quantum yield of PS2 photochemistry) and are significantly different from sun and shade leaves but could not be differentiated from each other. The mean values of the Chl fluorescence decrease ratio R Fd of blue-shade and half-shade leaves fit well into the strong linear correlation with the net photosynthetic rates P N of sun and shade leaves, thus unequivocally indicating that the determination of the Chl fluorescence decrease ratio R Fd is a fast and indirect measurement of the photosynthetic activity of leaves. The investigations clearly demonstrate that the photosynthetic capacity and pigment composition of leaves and chloroplasts strongly depend on the amounts and quality of light received by the leaves.

DEVELOPMENT OF CHLOROPLASTS AT HIGH AND LOW LIGHT QUANTA FLUENCE RATES

ABSTRACT Chloroplast ultrastructure, ratio of photosynthetic pigments and the chlorophyll fluorescence induction kinetics (Kautsky effect) of plants grown under high light (HL) and low light (LL) intensity and of sun and shade leaves were compared in order to find parameters which describe the differences between sun-type chloroplasts (HL-chloroplasts) and shade-type ones (LL-chloroplasts). The differences in ultrastructure between HL- and LL-chloroplasts can be quantified by measuring several parameters. As compared to LL-chloroplasts the HL-chloroplasts exhibit a lower frequency of thylakoids (in most plants), a higher proportion of exposed membranes, a lower stacking degree and lower values for the ratio between appressed to exposed membranes, a narrower grana width, fewer thylakoids per granum, a high starch content and a greater number and larger size of plastoglobuli. As compared to LL-chloroplasts, HL-chloroplasts are characterized by a higher chlorophyll a and (β-carotene content, which results in...

Allelochemical induces growth and photosynthesis inhibition, oxidative damage in marine diatom Phaeodactylum tricornutum

Algal blooms have been occurring in many regions all over the world and allelochemical is considered as one of the important and promising algaecides to control algal blooms. In the present study, we investigated the effects of allelochemical hydroquinone (HQ) on growth, photosynthesis and other physiological levels of Phaeodactylum tricornutum (P. tricornutum). The results showed that HQ (above 3×10−7mol/L) significantly inhibited the growth and specific growth rate of algae. EC50 values were calculated at four different incubation times, i.e. 24, 48, 72 and 96h. EC50 values increased with the treated-time increasing, which suggested that HQ stress on the algae gradually weakened with time prolonging. The contents of cellular pigments including Chlorophyll a (Chl.a) and carotenoids were significantly decreased by HQ. However, the ratios of carotenoids to Chl.a increased obviously when algae were exposed to 6 and 7×10−7mol/L of HQ for 72h, which implied that the ratios of pigments changed in extreme conditions to resist environmental stress. At the same time, HQ also induced the responses of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione S-transferase (GST) and non-enzymatic antioxidant reduced glutathione (GSH). Additionally, flow cytometric assays showed that HQ stress altered the permeability of cell membrane and mitochondrial membrane potential in different degrees and HQ significantly inhibited the transcription of photosynthesis and respiration related genes. All these results showed that HQ might have the potential as an algaecide to control marine microalgae.

Phycobilisome composition in Chondrus crispus (Gigartinales, Rhodophyta) from a wild type strain and its vegetatively derived green mutant

Intact phycobilisomes from a wild-type red Chondrus crispus and its vegetatively derived green mutant were isolated by centrifugation through a discontinuous sucrose density gradient. Pigment composition was subsequently characterized by spectrophotometry. Vegetative thalli of the two strains grown together for six months in the laboratory resulted in different pigment profiles. Two pigmented phycobilisome bands appeared in the sucrose gradient of the wild-type alga, a purple coloured one, and a pink one, whereas only a single blue band appeared in the gradient of the green mutant. Spectrophotometric and fluorescence analyses identified the phycobiliprotein composition of the purple band as the typical phycoerythrin-phycocyanin-allophycocyanin complement in the wild-type, but there was no detectable phycoerythrin present in the blue band of the green mutant. Sodium dodecyl sulphate, preparative polyacrylamide gel electrophoresis analysis confirmed the presence of allophycocyanin subunits in all extracts, but firm evidence of an R-phycoerythrin linker polypeptide in the blue band was missing. These results highlight the ability of C. crispus to adapt to a phycoerythrin deficiency by adjusting light harvesting pigment ratios.

Molecular and Photosynthetic Responses to Prolonged Darkness and Subsequent Acclimation to Re-Illumination in the Diatom Phaeodactylum tricornutum

Photosynthetic diatoms that live suspended throughout the water column will constantly be swept up and down by vertical mixing. When returned to the photic zone after experiencing longer periods in darkness, mechanisms exist that enable the diatoms both to survive sudden light exposure and immediately utilize the available energy in photosynthesis and growth. We have investigated both the response to prolonged darkness and the re-acclimation to moderate intensity white irradiance (E = 100 µmol m−2 s−1) in the diatom Phaeodactylum tricornutum, using an integrated approach involving global transcriptional profiling, pigment analyses, imaging and photo-physiological measurements. The responses were studied during continuous white light, after 48 h of dark treatment and after 0.5 h, 6 h, and 24 h of re-exposure to the initial irradiance. The analyses resulted in several intriguing findings. Dark treatment of the cells led to 1) significantly decreased nuclear transcriptional activity, 2) distinct intracellular changes, 3) fixed ratios of the light-harvesting pigments despite a decrease in the total cell pigment pool, and 4) only a minor drop in photosynthetic efficiency (ΦPSII_max). Re-introduction of the cells to the initial light conditions revealed 5) distinct expression profiles for nuclear genes involved in photosynthesis and those involved in photoprotection, 6) rapid rise in photosynthetic parameters (α and rETRmax) within 0.5 h of re-exposure to light despite a very modest de novo synthesis of photosynthetic compounds, and 7) increasingly efficient resonance energy transfer from fucoxanthin chlorophyll a/c-binding protein complexes to photosystem II reaction centers during the first 0.5 h, supporting the observations stated in 6). In summary, the results show that despite extensive transcriptional, metabolic and intracellular changes, the ability of cells to perform photosynthesis was kept intact during the length of the experiment. We conclude that P. tricornutum maintains a functional photosynthetic apparatus during dark periods that enables prompt recovery upon re-illumination.

The toxicity and intraspecific variability of Alexandrium andersonii Balech

The toxicity of Alexandrium andersonii Balech is unclear and its intraspecific variability has yet to be studied. To address these gaps in our knowledge, in the present work five strains of A. andersonii from four different localities were characterized. The results showed that despite genetic homogeneity in the 5.8-ITS (internal transcribed spacer) and large subunit (LSU) regions and similar growth rates, strains originating from different locations varied with respect to cell size, the ratios of certain pigments, and their growth patterns. Cultures of the strains grown at 20°C were analyzed for toxicity using four different methodologies. The two officially established methods, mouse bioassay and high-performance liquid chromatography with fluorescence detection (HPLC-FLD) and post-column reaction analysis of PSP toxins, failed to show the toxicity of any strain. Strains grown at 14°C were also negative for PSP toxins by HPLC-FLD. However, strains grown at 20°C exhibited both a response characteristic of the presence of toxin-inhibiting voltage-gated sodium channels, as demonstrated in a neuroblastoma neuro-2a cell-based assay, as well as hemolytic activity in a sheep red blood cell assay.

Photoacclimation and non-photochemical quenching under in situ irradiance in natural phytoplankton assemblages from the Amundsen Sea, Antarctica

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 475:15-34 (2013) - DOI: https://doi.org/10.3354/meps10097 Photoacclimation and non-photochemical quenching under in situ irradiance in natural phytoplankton assemblages from the Amundsen Sea, Antarctica Anne-Carlijn Alderkamp1,2,*, Matthew M. Mills1, Gert L. van Dijken1, Kevin R. Arrigo1 1Department of Environmental Earth System Science, Stanford University, Stanford, California 94019, USA 2Department of Ocean Ecosystems, Energy and Sustainability Research Institute, University of Groningen, 9747 AG, Groningen, The Netherlands *Email: alderkamp@stanford.edu ABSTRACT: Photoacclimation strategies and sensitivity to photoinhibition were determined in natural phytoplankton assemblages during a phytoplankton bloom in the Amundsen Sea (Southern Ocean) in relation to community composition, pigment content, light, and iron (Fe). Non-photochemical quenching (qN) was measured during recovery after surface irradiance exposure (SIE) for 20 min. The qN was separated into slow (qI, photoinhibition through damage of Photosystem II) and fast (qE, xanthophyll cycling) relaxing components. Phytoplankton within the upper mixed layer (UML) showed a higher ratio of photoprotective xanthophyll cycle pigments (diadinoxanthin [DD] + diatoxanthin [DT]) to chlorophyll a (chl a), indicative of acclimation to high light, which resulted in lower photoinhibition after SIE when compared to phytoplankton residing below the UML. Within the UML, we found differences in photoacclimation strategies in assemblages dominated by Antarctic diatoms versus Phaeocystis antarctica (Haptophyta). Diatoms had a higher ratio of (DD + DT)/chl a, and the ratio tracked mean light levels within the UML, whereas this relationship was not apparent in P. antarctica, which had a lower (DD + DT)/chl a ratio. Despite these differences, diatoms and P. antarctica exhibited similar degrees of qN that were dominated by qE with very little qI. Bioassays under high and low Fe concentrations revealed an increase in the (DD + DT)/chl a ratio in Fe-limited populations dominated by diatoms and decreased photoinhibition. In experiments dominated by P. antarctica or with mixed populations, acclimation to low Fe increased the (DD + DT)/chl a ratio in most experiments; however, this did not affect photoinhibition. This study shows that under in situ conditions in the Amundsen Sea (1) phytoplankton photoacclimation efficiently minimizes photoinhibition, (2) photoinhibition does not control the relative abundances of P. antarctica or Antarctic diatoms, and (3) Fe limitation does not increase photoinhibition of either P. antarctica or Antarctic diatoms. KEY WORDS: Amundsen Sea · Diatoms · Iron · Non-photochemical quenching · Phaeocystis antarctica · Photoacclimation · Photoinhibition · Xanthophyll cycle Full text in pdf format Supplementary material PreviousNextCite this article as: Alderkamp AC, Mills MM, van Dijken GL, Arrigo KR (2013) Photoacclimation and non-photochemical quenching under in situ irradiance in natural phytoplankton assemblages from the Amundsen Sea, Antarctica. Mar Ecol Prog Ser 475:15-34. https://doi.org/10.3354/meps10097 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 475. Online publication date: February 14, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Variability in light absorption and scattering of phytoplankton in Patagonian waters: Role of community size structure and pigment composition

Intense phytoplankton blooms were observed along the Patagonian shelf‐break with satellite ocean color data, but few in situ optical observations were made in that region. We examine the variability of phytoplankton absorption and particulate scattering coefficients during such blooms on the basis of field data. The chlorophyll‐a concentration, [Chla], ranged from 0.1 to 22.3 mg m−3 in surface waters. The size fractionation of [Chla] showed that 80% of samples were dominated by nanophytoplankton (N‐group) and 20% by microphytoplankton (M‐group). Chlorophyll‐specific phytoplankton absorption coefficients at 440 and 676 nm, a*ph(440) and a*ph(676), and particulate scattering coefficient at 660 nm, b*p(660), ranged from 0.018 to 0.173, 0.009 to 0.046, and 0.031 to 2.37 m2 (mg Chla)−1, respectively. Both a*ph(440) and a*ph(676) were statistically higher for the N‐group than M‐group and also considerably higher than expected from global trends as a function of [Chla]. This result suggests that size of phytoplankton cells in Patagonian waters tends to be smaller than in other regions at similar [Chla]. The phytoplankton cell size parameter, Sf, derived from phytoplankton absorption spectra, proved to be useful for interpreting the variability in the data around the general inverse dependence of a*ph(440), a*ph(676), and b*p(660) on [Chla]. Sf also showed a pattern along the increasing trend of a*ph(440) and a*ph(676) as a function of the ratios of some accessory pigments to [Chla]. Our results suggest that the variability in phytoplankton absorption and scattering coefficients in Patagonian waters is caused primarily by changes in the dominant phytoplankton cell size accompanied by covariation in the concentrations of accessory pigments.

Algorithm development for predicting biodiversity based on phytoplankton absorption

Ocean color remote sensing has provided the scientific community with unprecedented global coverage of chlorophyll a, an indicator of phytoplankton biomass. Together, satellite-derived chlorophyll a and knowledge of Phytoplankton Functional Types (PFTs) will improve our limited understanding of marine ecosystem responses to physiochemical climate drivers involved in carbon cycle dynamics and linkages. Using cruise data from the Gulf of Maine and the Middle Atlantic Bight (N=269 pairs of HPLC and phytoplankton absorption samples), two modeling approaches were utilized to predict phytoplankton absorption and pigments. Algorithm I predicts the chlorophyll-specific absorption coefficient (aph⁎ (m2mgchla−1)) using inputs of temperature, light, and chlorophyll a. Modeled r2 values (400–700nm) ranged from 0.79 to 0.99 when compared to in situ observations with ∼25% lower r2 values in the UV region. Algorithm II-a utilizes matrix inversion analysis to predict aph(m−1, 400–700nm) and r2 values ranged from 0.89 to 0.99. The prediction of phytoplankton pigments with Algorithm II-b produced r2 values that ranged from 0.40 to 0.93. When used in combination, Algorithm I, and Algorithm II-a are able to use satellite products of SST, PAR, and chlorophyll a (Algorithm I) to predict pigment concentrations and ratios to describe the phytoplankton community. The results of this study demonstrate that the spatial variation in modeled pigment ratios differ significantly from the 10-year SeaWiFS average chlorophyll a data set. Contiguous observations of chlorophyll a and phytoplankton biodiversity will elucidate ecosystem responses with unprecedented complexity.

The Effect of Fucus vesiculosus L. (Phaeophyceae) Depth of Vegetation in the Barents Sea (Russia) on Its Morphophysiological Parameters

Investigation of species composition of epiphytes and phytophages, thalus morphology, growth rate, intensity of photosynthesis, composition and ratio of photosynthetic pigments, metabolic activity of cells of brown seaweed Fucus vesiculosus, placed on depths from 0 to 15 m, was carried out. Results of the study have shown that in the absence of interspecific competition, the depth of 0.5 m is most favorable for F. vesiculosus growth in the Barents Sea.

Study on the Effect of Pigment Dispersion on Water-based Ink Rheological Property

With the widely development of digital printing technology and the enhancement of environmental awareness, more and more people in digital printing industry pay attention to environmentally friendly water-based ink. Water-based ink is a kind of dispersed system that made of pigment particles, water, resin and various additives, and dispersion is one important factor that affects the rheological properties of ink. In order to explore the influence of the dispersion of pigment on the rheological properties of water-based ink, we change the grinding time and the ratio of pigment to resin to prepare ink samples with different dispersion state. The particle size distribution of the samples is tested by laser particle size analyzer and the rheological parameters such as viscosity and thixotropy, of the samples are tested by ARES rheometer, and analyze the effect of dispersion on rheological properties of ink. The experiment results show that the ratio of pigment to resin influences the dispersion state seriously, at the same time dispersion state has a great influence on the rheological properties.

Influence of Inkjet Paper Coating Structure on Paper Properties and Print Performance

The influence of coating layer structure on both physical and printing quality of the paper was studied. Different coating layers were obtained by changing the ratio of polyvinyl alcohol adhesives and silicon dioxide pigments in the coating formula. Then the structure, physical properties and ink-jet printing performance of the coated paper were measured. The influences of coating structure on physical properties and ink-jet printing performance were evaluated. The results showed that as the ratio of adhesive increased, the coating porosity decreased; the average pore diameter increased at first and then decreased, but in general tended to decrease; the initial drop contact angle increased, which testified the stronger hydrophobicity of the coated surface with higher adhesive ratio. The average pore diameter has a negative linear correlation with paper roughness while has a positive linear correlation with air permeability. The larger the average pore diameter, the greater the density values, as well as the better tone reproduction and the larger color gamut range. Average pore diameter also has a weak correlation with dot area and dot roundness.

Study on the Dispersity of Black Water-Based Covering Ink

Dispersity is one of the most important factors that affect the covering property of ink. In order to obtain the black water-based ink with high covering property, study the dispersity of ink, by changing the variety of both pigments and resins, the ratio of pigment to resin, the variety and the content of dispersants to prepare based ink, by testing the diameter size to explore the factors that affect the dispersion of black water-based covering ink. It has been proved that the interaction between different pigments and resins is the key factor that influences the dispersion property of the black water-based covering ink. The dispersity property of the resin to pigment depends on a great extent on the ratio of pigment to resin. The result also proved that different kind of dispersants and content are also important factors that influence the dispersion property.

Influence of local environmental conditions on the seasonal acclimation process and the daily integrated production rates of Laminaria digitata (Phaeophyta) in the English Channel

Two populations of Laminaria digitata (Hudson) Lamouroux (Ann Mus Hist Nat Paris 20:21–47, 1813) were examined for their seasonal photosynthetic acclimation to clear and turbid-light environments along the French coast of the English Channel. Photosynthesis–irradiance curves, pigment concentrations and the daily in situ integrated oxygen production rates were measured in both populations. Despite the great differences in light attenuation between the sites, the two populations achieved similar oxygen production rates in the field, in relation to high maximal photosynthetic rates, total pigment concentrations and antenna (fucoxanthin + chlorophyll c)/chl a pigment ratios in sporophytes from the turbid environment. Environmental conditions (i.e. light, temperature and nitrogen availability) changed throughout the year in both sites. While the seasonal acclimation trends were evident in the clear-light environment, the strategy in the turbid-light environment differed, tending to maximize light capture throughout the year. This study highlights the diversity of the response of a single species to contrasted light environments.

Algal Biogeography: Metagenomics Shows Distribution of a Picoplanktonic Pelagophyte

How can we determine the distribution of uncultured marine microorganisms? Targeted metagenomics has provided the complete chloroplast genome sequence, and the distribution, for a picoplanktonic pelagophyte alga.

Simultaneous Decoloration and Deproteinization of Crude Polysaccharide from Pumpkin Residues by Cross-Linked Polystyrene Macroporous Resin

A novel method for the purification of crude polysaccharide from fermentation broth of pumpkin residues by macroporous resins was developed. Through static adsorption and desorption and adsorption kinetic tests, six resins (AB-8, S-8, HPH480, HPD100, X-5, and D101) with different polarity, diameter, and surface area were studied for simultaneous decoloration and deproteinization of crude polysaccharide, and S-8 was chosen as the best one. Dynamic breakthrough and desorption tests were performed in a glass column packed with S-8 resin, and the resulting adsorption ratios of pigment and protein were 84.3% and 75.9% (w/w), respectively, with a recovery ratio of polysaccharide 84.7% (w/w). S-8 resin also exhibited higher purification efficiency than the other tested traditional methods. Moreover, UV/vis spectroscopy (200-900 nm) analysis revealed most of the pigment and protein were absorbed by S-8 resin, and HPLC (containing a refractive index detector and a HPSEC column) results indicated that there was no degradation of the polysaccharide. This automated and efficient method via adsorption-desorption strategy could have potential in scale-up purification and preparation of polysaccharide in the future.

Redox alters yellow dragonflies into red

Body color change associated with sexual maturation--so-called nuptial coloration--is commonly found in diverse vertebrates and invertebrates, and plays important roles for their reproductive success. In some dragonflies, whereas females and young males are yellowish in color, aged males turn vivid red upon sexual maturation. The male-specific coloration plays pivotal roles in, for example, mating and territoriality, but molecular basis of the sex-related transition in body coloration of the dragonflies has been poorly understood. Here we demonstrate that yellow/red color changes in the dragonflies are regulated by redox states of epidermal ommochrome pigments. Ratios of reduced-form pigments to oxidized-form pigments were significantly higher in red mature males than yellow females and immature males. The ommochrome pigments extracted from the dragonflies changed color according to redox conditions in vitro: from red to yellow in the presence of oxidant and from yellow to red in the presence of reductant. By injecting the reductant solution into live insects, the yellow-to-red color change was experimentally reproduced in vivo in immature males and mature females. Discontinuous yellow/red mosaicism was observed in body coloration of gynandromorphic dragonflies, suggesting a cell-autonomous regulation over the redox states of the ommochrome pigments. Our finding extends the mechanical repertoire of pigment-based body color change in animals, and highlights an impressively simple molecular mechanism that regulates an ecologically important color trait.