Mixture Of Carotenoids Research Articles

Tuning bio-derived solvents for the rapid solubilization of astaxanthin-rich extracts from non-conventional bacterium Paracoccus carotinifaciens

Astaxanthin (AXT) is a ketocarotenoid widely used in food, feed, and pharmaceutical industries. Its biological sourcing is preferred over chemical methods due to higher physiological and commercial value. Paracoccus carotinifaciens, an aerobic marine Gram-negative bacterium, is known for producing a carotenoid mixture with AXT as the main component. This study explores the use of bio-based solvents, both pure and mixed, for extracting AXT-rich extracts (ARE). Using COSMO-SAC, a quantum chemistry-based thermodynamic model, we assessed the AXT-solvent affinity. The ethyl acetate: acetic acid mixture (EtOAc:AA) gave the best results, with 1.41 mg/mL of ARE. The solvent selection process was evaluated through the Eco Scale to compare with conventional methods. Next, optimization of extraction conditions resulted in 3.28 mg/mL of ARE at 78 °C, 10 min, and a solid-to-liquid ratio of 0.5 g/mL. Ultrasound-assisted extraction (UAE) was employed to tuning the mass-transfer process, leading to an increase of ARE (18.9 %) in reduced processing time. Concerning the stability of ARE in the EtOAc:AA mixture, the half-life (t1/2) reached 18 and 26 days under the light and dark conditions, respectively at 25 °C. In both light and dark conditions, positive enthalpy (ΔH) values revealed an endothermic process and both entropy (ΔS) and Gibbs free energy (ΔG) values suggest that the degradation of ARE is less disordered and non-spontaneous process. The solvent mixture was effectively reused for three cycles under optimally tuned conditions without a significant decline of ARE extraction efficiency.

Modulating spectral response of raw photosynthetic pigments via ternary cadmium chalcogenide quantum dots: simultaneous enhancement at green spectrum and inhibition at UV region.

Photosynthesis relies on the absorption of sunlight by photosynthetic pigments (PPs) such as chlorophylls and carotenoids. While these pigments are outstanding at harvesting light, their natural structure restricts their ability to harvest light at specific wavelengths. In this study, Oleic acid-capped CdSeS and CdTeS ternary quantum dots (QDs) were synthesized using a novel two-phase synthesis method. Then, these QDs were used to interact with raw PPs, a mixture of chlorophylls and carotenoids isolated from spinach. Our findings revealed the following: (1) Interacting QDs with raw PPs effectively inhibited the chlorophyll fluorescence of the pigments upon excitation in UV light region (250-400nm) without causing any damage to their structure. (2) By forming an interaction with QDs, the chlorophyll fluorescence of raw PPs could be induced through excitation with green-light spectrum. (3) The composition of the QDs played a fundamental role in their interaction with PPs. Our study demonstrated that the photophysical properties of isolated PPs could be modified by using cadmium-based QDs by preserving the structure of the pigments themselves.

Identification of a novel monocyclic carotenoid and prediction of its biosynthetic genes in Algoriphagus sp. oki45

Bacteria belonging to the genus Algoriphagus have been isolated from various sources, such as Antarctic sea ice, seawater, and sediment, and some strains are known to produce orange to red pigments. However, the pigment composition and biosynthetic genes have not been fully elucidated. A new red-pigmented Algoriphagus sp. strain, oki45, was isolated from the surface of seaweed collected from Senaga-Jima Island, Okinawa, Japan. Genome comparison revealed oki45’s average nucleotide identity of less than 95% to its closely related species, Algoriphagus confluentis NBRC 111222 T and Algoriphagus taiwanensis JCM 19755 T. Comprehensive chemical analyses of oki45’s pigments, including 1H and 13C nuclear magnetic resonance and circular dichroism spectroscopy, revealed that the pigments were mixtures of monocyclic carotenoids, (3S)-flexixanthin ((3S)-3,1′-dihydroxy-3′,4′-didehydro-1′,2′-dihydro-β,ψ-caroten-4-one) and (2R,3S)-2-hydroxyflexixanthin ((2R,3S)-2,3,1′-trihydroxy-3′,4′-didehydro-1′,2′-dihydro-β,ψ-caroten-4-one); in particular, the latter compound was new and not previously reported. Both monocyclic carotenoids were also found in A. confluentis NBRC 111222 T and A. taiwanensis JCM 19755 T. Further genome comparisons of carotenoid biosynthetic genes revealed the presence of eight genes (crtE, crtB, crtI, cruF, crtD, crtYcd, crtW, and crtZ) for flexixanthin biosynthesis. In addition, a crtG homolog gene encoding 2,2ʹ-β-hydroxylase was found in the genome of the strains oki45, A. confluentis NBRC 111222 T, and A. taiwanensis JCM 19755 T, suggesting that the gene is involved in 2-hydroxyflexixanthin synthesis via 2-hydroxylation of flexixanthin. These findings expand our knowledge of monocyclic carotenoid biosynthesis in Algoriphagus bacteria.Key points• Algoriphagus sp. strain oki45 was isolated from seaweed collected in Okinawa, Japan.• A novel monocyclic carotenoid 2-hydroxyflexixanthin was identified from strain oki45.• Nine genes for 2-hydroxyflexixanthin biosynthesis were found in strain oki45 genome.Graphical

CAROTENOID-ENRICHED DIET FOR PREMATURATION STAGE OF POND- REARED TIGER SHRIMP, Penaeus monodon: Part II. EFFECT ON GONADAL MATURATION AND BIOCHEMICAL PROFILES OF OOCYTES, SPERMATOPHORES AND HEPATOPANCREAS

Two-phase feeding trials were conducted to evaluate the effect of the carotenoid mixture on gonadal development and biochemical properties of several tissues of tiger shrimp. The treatments were diet enriched with (PC) and without carotenoid mixture (PO). Shrimp with an initial body weight of 31.7±1.3 g were allocated among four of 1,000 m2 concrete ponds with a density of 1 shrimp/m2 and fed tested diets for five months. Selected shrimps from the pond with a minimum weight of 80 g for females and 60 g for males were stocked into four 10-m3 concrete tanks at 15 pairs per tank. Natural mating rate and ovary development were not stimulated by the carotenoid supplement. However, it significantly improved (P<0.05) both ovary maturation and spermatophore formation of tiger shrimp from 76.7±1.4 to 86.7±0.0% and from 69.9 ±4.5 to 82.3±4.0%, respectively. Total carotenoid content in meat, oocyte and hepatopancreas of female tiger shrimp significantly (P<0.05) increased by supplementing carotenoid compared to the control diet. The total amino acid content in the spermatophore of shrimp fed the PC diet was significantly higher (73.82%) than in the PO diet (66.09%). The present study revealed the important effect of carotenoid feed during the pre-maturation stage on the reproductive performances of pond-reared tiger shrimp.

Mass Species of the Sea Star Asterina Pectinifera as a Potential Object of Mariculture

Starfish Asterina (= Patiria) pectinifera) is widely distributed along the western coast of the Pacific Ocean from Sakhalin Island to the Yellow Sea. This is the most numerous species in the Peter the Great Bay of the Sea of Japan. Asterina tissues in large quantities contain a mixture of carotenoids, the most famous of which is astaxanthin. The developed technology of complex processing of A. pectinifera starfish allows to obtain biologically active collagen peptides and carotenoid preparations enriched with astaxanthin, exhibiting immunomodulatory, anti-inflammatory and antioxidant activities. They can be used as a raw material for obtaining new medicinal, cosmetic and food products.

Mouse Models to Study Antiobesogenic Effects of Carotenoids.

Carotenoids entail a vast potential to tackle health problems including obesity and some of its comorbidities. The use of animal models remains necessary, particularly at early stages of research (preclinical) and for advancing in mechanistic aspects of carotenoid action. No single animal model completely mimics human absorption and metabolism of carotenoids, and the best model must be chosen considering the specific application, characteristics of the individual models, and funding and facilities available. Here, we propose three protocols in mice to investigate the potential of a given carotenoid, carotenoid mixture, or carotenoid-rich extract to (a) counteract the development of obesity and prevent the metabolic alterations caused by feeding mice a moderate high-fat diet; (b) improve the metabolic profile of obese animals with metabolic alterations caused by chronic high-fat diet feeding; and (c) act as coadjuvants in weight loss strategies (reversion to a low fat diet) applied to diet-induced obese animals.

Carotenoid composition and conformation in retinal oil droplets of the domestic chicken.

Carotenoid-containing oil droplets in the avian retina act as cut-off filters to enhance colour discrimination. We report a confocal resonance Raman investigation of the oil droplets of the domestic chicken, Gallus gallus domesticus. We show that all carotenoids present are in a constrained conformation, implying a locus in specific lipid binding sites. In addition, we provide proof of a recent conclusion that all carotenoid-containing droplets contain a mixture of all carotenoids present, rather than only a subset of them—a conclusion that diverges from the previously-held view. Our results have implications for the mechanism(s) giving rise to these carotenoid mixtures in the differently-coloured droplets.

Effect of 2-year nutritional supplementation on progression of age-related macular degeneration.

To examine the effect of a long-term nutritional supplementation on age-related macular degeneration progression. In this prospective, double-blind, placebo-controlled study, 80 patients with intermediate age-related macular degeneration were randomized (2:1) to receive 1 tablet/day of a nutritional supplement containing a mixture of carotenoids, vitamins and omega-3 fatty acids or placebo. Age-related macular degeneration progression assessed by digital fundus photography (primary outcome) and best-corrected visual acuity were evaluated. Differences between arms were tested using chi-square test or Fisher's exact test. Seventy-four patients completed the follow-up at 24 months (48 in the treated arm and 26 in the placebo arm). An age-related macular degeneration progression was observed in the 2.1% of patients of the treated arm and in the 15.4% of patients in the placebo arm (p = 0.05, Fisher's exact test). Best-corrected visual acuity data alone were not statistically significant among groups. A clinically meaningful stabilization of intermediate age-related macular degeneration over a period of 2 years may be obtained by treating patients with a mixture of carotenoids, vitamins and omega-3 fatty acids.

Analyzing carotenoids of snow algae by Raman microspectroscopy and high-performance liquid chromatography.

We tested the potential of Raman microspectroscopy to determine carotenoid pigments - both primary (lutein, beta-carotene) and secondary (astaxanthin) carotenoids - in the different species and life-cycle stages of snow algae from the order Chlamydomonadales (Chlorophyta). We compared the performance of Raman spectrometry to a reference method of biological pigment analysis, high-performance liquid chromatography (HPLC). The three main carotenoid Raman bands of the astaxanthin-rich red cysts were located at 1520, 1156 and 1006 cm-1. The shifts (orange aplanozygotes and green motile cells with flagella) in the position of the ν1(CC) Raman band of the polyenic chain is consistent with the expected changes in the ratios of the various carotenoid pigments. Flagellated green cells commonly contain lutein as a major carotenoid, together with minor amounts of β‑carotene and varying amounts of antheraxanthin, violaxanthin and neoxanthin. Aplanozygotes contain mixtures of both primary and secondary carotenoids. In most cases, the ν1(CC) band is an overlapping set of bands, which is due to the signal of all carotenoid pigments in the sample, and a deconvolution along with the band position shifts (mainly ν1) could be used to characterize the mixture of carotenoids. However, the ability of Raman spectroscopy to discriminate between structurally slightly differing carotenoid pigments or several carotenoids in an admixture in an unknown biological system remains limited.

Selection of bacterial strains belonging to the astaxanthin producing Paracoccus genus

Astaxanthin, a member of the carotenoid group, is an important additive not only in feed nutrition but also in providing the red color of salmon meat, cooked shellfish and koi fish. This leads to an increase in the commercial and aesthetic values for those aquatic products. In addition, astaxanthin is widely used in the food, pharmaceutical and cosmetic industries. Nowadays, astaxanthin has been mainly extracted from Haematococcus pluvialis and Phaffia rhodozyma. Moreover, some bacterial groups, especially Paracoccus genus including P. carotinifaciens, and P. haeundaensis have also been reported to synthesize a high level of astaxanthin. In this study, a number of bacterial strains belonging to Paracoccus genus isolated from several in-shore regions of Vietnam have been screened to find high astaxanthin producing strains for aquatic feed production. More than 90 colourful biosynthesis strains were isolated from 50 soil and water samples in different beaches and ramsa, of which 33 strains belong to negative bacterial group. Analysis of the extracted carotenoid mixtures obtained from the pellets of those strains by UV-Vis spectrophotometer and TLC reveals that 3 strains including C32, C38 and C47 are able to yield a high level of astaxanthin at 23 mg, 18 mg, and 11 mg astaxanthin per 1 g biomass, respectively. Based on the physiological, biochemical and 16S rRNA gene sequence, the C32 and C38 strains are most related to P. carotinifaciens whereas the C47 strain is most closely to P. kocurii.

Predicting organ carotenoids levels from analysis of plasma could lead to errors: A study in cynomolgus monkeys

Carotenoids are phytochemicals with strong antioxidant activity against reactive oxygen species that are widely distributed in fruits and vegetables. The beneficial effects of carotenoids on human health have attracted considerable attention. The plasma carotenoid profile in humans is generally recognized to reflect the dietary carotenoid composition. Although carotenoid profile in plasma is believed to correlate well with that in other tissues, the data for tissue accumulation of carotenoids in humans is very limited and poorly understood. In order to test the hypothesis that blood carotenoids reflect tissue accumulation of dietary carotenoids, the cynomolgus monkey was used as a model to determine it's suitable for extrapolation of data on tissue accumulation of carotenoids to humans. Herein, plasma carotenoids were measured in cynomolgus monkeys given a dietary mixture of carotenoids. The findings indicate that cynomolgus monkeys and humans are similar with regard to preferential accumulation of β-cryptoxanthin in the blood and brain. These results suggested that cynomolgus monkeys could be used to collect data on tissue accumulation of carotenoids for extrapolation to humans. The tissue accumulation of carotenoids in other tissues of cynomolgus monkeys that have not yet been evaluated in humans were also investigated, revealing marked differences in carotenoid levels and composition among plasma and various monkey tissues. These results suggest that accumulation of carotenoids in plasma does not reflect necessarily that in tissues, so that predicting the tissue accumulation of carotenoids from plasma carotenoid levels and profiles alone could lead to errors.

Nature of light-absorbing pigments from Brazilian lichens identified by Raman spectroscopy

Light-absorbing pigments from different chemical classes have been identified from the lichens Usnea sp. and Crocodia aurata using Raman spectroscopy supported by quantum mechanical DFT calculations. Raman spectra were obtained directly from the lichen tissues as well as from isolated extracts. Usnic acid, a chemomarker of Usnea spp has been reported together with a minor constituent, namely stictic acid, which has been unambiguously identified by 1H and 13C NMR spectral analysis. The structures of calycin and pulvinic dilactone isolated from Crocodia aurata have been confirmed by single crystal X-ray diffraction. The ubiquitous carotenoids have been characterized by FT-Raman and dispersive Raman microimaging in tissues of Usnea sp. and C. aurata, respectively. The Raman map has revealed the presence of a mixture of carotenoids heterogeneously distributed in the upper layer of C. aurata. In this work we have demonstrated that Raman spectroscopy can be used to monitor aromatic and conjugated polyenic pigments in different layers of lichen tissues.

Determination of Carotenoids in Infant, Pediatric, and Adult Nutritionals by HPLC with UV-Visible Detection: Single-Laboratory Validation, First Action 2017.04.

This reversed-phase HPLC method uses C30 chromatography and UV-Vis spectroscopy to determine cis and trans isomers of lutein, β-carotene, and lycopene in infant, pediatric, and adult nutritionals. Samples are saponified with a mixture of potassium hydroxide, tetrahydrofuran, and methanol, and carotenoids are extracted from saponified samples with 75 + 25 hexane-methyl tertiary butyl ether (MtBE). After extraction, a portion of the organic layer is evaporated to dryness, and the residue is dissolved in 75 + 25 10% butylated hydroxytoluene in methanol-MtBE. Prepared samples are injected into a C30 HPLC column where cis and trans isomers of lutein, β-carotene, and lycopene are separated with a methanol-MtBE gradient and detected with UV-Vis spectroscopy at 445 nm. Total carotenoid concentrations are calculated by comparison of sample peak areas with the areas of trans carotenoid standards of known concentration. During a single-laboratory validation of this method, total lutein repeatability and intermediate precision ranged from 1.89 to 14.9 and 1.93 to 14.0%, respectively, in infant and adult nutritional matrixes with concentrations >1 μg/100 g. Total β-carotene repeatability and intermediate precision ranged from 1.81 to 6.77 and 3.07 to 16.2%, respectively, in infant and adult nutritional matrixes with concentrations >1 μg/100 g, and total lycopene repeatability and intermediate precision ranged from 3.01 to 6.37 and 4.29 to 10.3%, respectively, in infant and adult nutritional matrixes with concentrations >1 μg/100 g. Mean overspike recoveries ranged from 90.3 to 95.3, 89.3 to 108, and 97.3 to 109% for lutein, β-carotene, and lycopene, respectively. The method also demonstrated good linearity. For lutein, r averaged 0.99991 over a standard range of approximately 10-250 µg/L trans-lutein. with average calibration errors of <1%. For β-carotene and lycopene, r averaged 0.99993 and 0.9998 over standard ranges of approximately 25-500 and 5-100 µg/L with calibration errors of <1 and <1.5%, respectively. Lutein, β-carotene, and lycopene LOQs in ready-to-feed nutritionals were estimated to be 0.4, 0.1, and 0.3 µg/100 g, respectively. This method met AOAC Stakeholder Panel on Infant Formula and Adult Nutritionals Standard Method Performance Requirements and was approved as a First Action Official Method at the AOAC INTERNATIONAL 2017 midyear meeting.

CAROTENOID-ENRICHED DIET FOR PRE-MATURATION STAGE OF POND-REARED TIGER SHRIMP, Penaeus monodon PART I. THE EFFECTS ON GROWTH, PIGMENTATION AND WHOLE BODY NUTRIENT CONTENT

Carotenoids, besides as a natural pigment, may have vital roles in the growth of crustacean. The aim of this study was to clarify the influence of combined carotenoids given since pre-maturation stage on the growth performances, pigmentation and biochemical composition of the whole body of pond-reared tiger shrimp, Penaeus monodon. Two experimental diets were supplemented with or without carotenoid mixture consisting of astaxanthin, canthaxanthin and other carotenoids contained in Spirulina. The carotenoid mixture was supplemented in the commercial diet normally used as a starter feed for tiger shrimp, re-pelleted and fed to tiger shrimp with an initial body weight of 31.7±1.3 g. Shrimp were stocked in four 1,000 m2 concrete ponds with a density of 1 shrimp/m2 and fed until the shrimp reached maturation stage (broodstock size). Variables observed were growth performances and pigmentation properties during the pre-maturation stage and total carotenoid content in several tissues of the female broodstock after being fed with the diets until maturation stage. After 16 weeks, shrimp fed with carotenoid-enriched diet (PC) diet produced significantly (P&lt;0.05) higher biomass than the diet without the enrichment (PO). The color of raw shrimp fed with PC diet was darker with greenish-brown compared to shrimp fed PO diet which was greenish blue. The visual appearances of 3-min steamed shrimp produced the color of red-orange for shrimp fed carotenoid compared to orange-yellow for control PO. The total carotenoid content in the whole body of shrimp fed PC diet were significantly (P&lt;0.05) enhanced compared to control PO diet which was 42.8 ±5.8 and 55.8± 5.1 µg/g for PO and PC diet, respectively. Supplemental carotenoid in the pre-maturation diet increased the biomass production from 23.1±1.9 kg to 30.2 ±0.1 kg and enhanced the color of the shrimp which was in line with carotenoid content in the whole body of pond-reared tiger shrimp.

Spirilloxanthin incorporation into the LH2 and LH1-RC pigment-protein complexes from a purple sulfur bacterium Allochromatium minutissimum

Incorporation of spirilloxanthin into carotenoidless LH2 and LH1-RC complexes from a purple sulfur bacterium Allochromatium (Alc.) minutissimum was studied. Carotenoidless cells of Alc. minutissimum were obtained using diphenylamine, a carotenoid biosynthesis inhibitor. In the course of incorporation of the carotenoid mixture, the composition of which corresponded to that of Alc. minutissimum control photosynthetic membranes, no selective incorporation of spirilloxanthin into the LH1-RC complex was detected. It is assumed that in vivo carotenoids are not incorporated into the LH2 and LH1-RC complexes from a common pool. Pure spirilloxanthin destroys both the LH2 and LH1-RC complexes. Within the concentration range of spirilloxanthin in the incorporated mixture from 27% to 52%, it was found to be incorporated into the LH2 and LH1-RC complexes with the efficiency of 13% and 33%, respectively. The possible existence of different sites of assembly for the LH2 and LH1-RC complexes is discussed, as well as of two fractions of LH2 complexes, in one of which rhodopin may be integrated, and in the other (minor) one, spirilloxanthin.

Combined Effects of Curcumin and Lycopene or Bixin in Yoghurt on Inhibition of LDL Oxidation and Increases in HDL and Paraoxonase Levels in Streptozotocin-Diabetic Rats.

Combination therapy using natural antioxidants to manage diabetes mellitus and its complications is an emerging trend. The aim of this study was to investigate the changes promoted by treatment of streptozotocin (STZ)-diabetic rats with yoghurt enriched with the bioactives curcumin, lycopene, or bixin (the latter two being carotenoids). Antioxidants were administered individually, or as mixtures, and biomarkers of metabolic and oxidative disturbances, particularly those associated with cardiovascular risk, were assessed. Treatment of STZ-diabetic rats with natural products individually decreased glycemia, triacylglycerol, total-cholesterol, oxidative stress biomarkers, including oxidized low-density lipoprotein (ox-LDL), and increased the activities of antioxidant enzymes. Individual carotenoids increased both high-density lipoprotein (HDL) and paraoxonase levels, whereas curcumin increased only paraoxonase. Treatments with mixtures of curcumin and lycopene or bixin had combined effects, decreasing biomarkers of carbohydrate and lipid disturbances (curcumin effect), increasing the HDL levels (carotenoids effects) and mitigating oxidative stress (curcumin and carotenoids effects). The combined effects also led to prevention of the LDL oxidation, thereby mitigating the cardiovascular risk in diabetes. These findings provide evidence for the beneficial effect of curcumin and carotenoid mixtures as a supplementation having antioxidant and antiatherogenic potentials, thus appearing as an interesting strategy to be studied as a complementary therapy for diabetic complications.

Distribution of rhodopin and spirilloxanthin between LH1 and LH2 complexes when incorporating carotenoid mixture into the membrane of purple sulfur bacterium Allochromatium minutissimum in vitro.

Carotenoid mixture enriched by rhodopin and spirilloxanthin was incorporated in LH2 and LH1 complexes from Allochromatium (Alc.) minutissimum in vitro. The maximum incorporating level was ~95%. Rhodopin (56.4%) and spirilloxanthin (13.8%) were incorporated into the LH1 complex, in contrast to the control complex, which contained primarily spirilloxanthin (66.8%). After incorporating, the LH2 complex contained rhodopin (66.7%) and didehydrorhodopin (14.6%), which was close to their content in the control (67.4 and 20.5%, respectively). Thus, it was shown that carotenoids from the total pool are not selectively incorporated into LH2 and LH1 complexes in vitro in the proportion corresponding to the carotenoid content in the complexes in vivo.

Effect of pectin concentration and properties on digestive events involved on micellarization of free and esterified carotenoids

Pectins with different chemical and rheological properties were added at two concentration levels into digestion reactions of soybean oil enriched with a mixture of free and esterified carotenoids to study their effects on several events involved on carotenoid micellarization. High pectin concentration increased lipolysis, viscosity of the gastrointestinal medium, and particle size but decreased carotenoid micellarization. At low concentration, pectin showed a high binding of bile salts and favored carotenoid micellarization. Pectins with high molecular weight and viscosity in model solutions substantially increased the viscosity of the intestinal media and the micellarization of the less polar carotenoids while pectins with high and medium degree of methyl esterification promoted lipolysis, bile binding, viscosity and large sizes of lipid droplets, and slightly favored the micellarization of the more polar carotenoids. The effects of pectin properties and amount on carotenoid micellarization seemed to be related to carotenoid speciation.

PHOTOSTABILITY OF PURPLE BACTERIAL LIGHT–HARVESTING COMPLEXES TOWARDS EXPOSURE OF LIGHT ILLUMINATION TRACED BY PIGMENT RATIO

Purple photosynthetic light–harvesting (LH2) is an attractive complex module for assembling hybrid nanostructures that feature energy transfer. LH2 has a broad absorption spectrum range from ultraviolet (UV) to near-infra red (NIR) region. Bacteriochlorophyll a molecules absorb at 320 nm to 400 nm (Soret band), 585 nm (Qx) and at NIR region (B800 and B850 bands), while carotenoid absorption bands span from 400 nm to 550 nm. LH2 has to be extracted from its native lipid bilayer membrane and placed in suitable matrix that less mobile and better adherent than the native lipid environment to determine its function. Previous results on pigment ratio determination in different strains of purple photosynthetic bacteria suggested a variation during initial log phase and late log phase. In this experiment, the goal is to reveal the behavior of pigment ratio in LH2 of Rhodopseudomonas palustris during irradiation of certain intensity of light. Photostability assay of LH2 from Rhodopseudomonas palustris in n-dodecyl-β-D-maltoside or DDM was determined under continuous illumination (3 000 μmol·m–2·s–1) for 300 min at room temperature by recording the absorption spectra. Degradation was observed in B850 and B800 at about 67 % and 64 %, respectively, as well as blue shift in B850. Initial pigments isolated from LH2 suggested a mixture of carotenoids and bacteriochlorophylls which was determined further using a high-performance liquid chromatography (HPLC).

A complex carotenoid palette tunes avian colour vision

The brilliantly coloured cone oil droplets of the avian retina function as long-pass cut-off filters that tune the spectral sensitivity of the photoreceptors and are hypothesized to enhance colour discrimination and improve colour constancy. Although it has long been known that these droplets are pigmented with carotenoids, their precise composition has remained uncertain owing to the technical challenges of measuring these very small, dense and highly refractile optical organelles. In this study, we integrated results from high-performance liquid chromatography, hyperspectral microscopy and microspectrophotometry to obtain a comprehensive understanding of oil droplet carotenoid pigmentation in the chicken (Gallus gallus). We find that each of the four carotenoid-containing droplet types consists of a complex mixture of carotenoids, with a single predominant carotenoid determining the wavelength of the spectral filtering cut-off. Consistent with previous reports, we find that the predominant carotenoid type in the oil droplets of long-wavelength-sensitive, medium-wavelength-sensitive and short-wavelength-sensitive type 2 cones are astaxanthin, zeaxanthin and galloxanthin, respectively. In addition, the oil droplet of the principal member of the double cone contains a mixture of galloxanthin and two hydroxycarotenoids (lutein and zeaxanthin). Short-wavelength-absorbing apocarotenoids are present in all of the droplet types, providing filtering of light in a region of the spectrum where filtering by hydroxy- and ketocarotenoids may be incomplete. Thus, birds rely on a complex palette of carotenoid pigments within their cone oil droplets to achieve finely tuned spectral filtering.