Separation and identification of astaxanthin esters and chlorophylls in Haematococcus lacustris by HPLC

Summary An isocratic reverse-phase high performance liquid chromatographic method was developed for the separation of carotenoids and chlorophylls from extracts of Haematococcus lacustris. Astaxanthin monoesters are the principal carotenoids in Haematococcus lacustris. Five astaxanthin monoesters, which accounted for 79% of the total carotenoids, were identified and the individual contents were determined by HPLC to be 7.3, 24.9, 6.1, 49.4 and 12.3% of the total astaxanthin monoesters, respectively. The maximum absorption wavelengths of the five astaxanthin monoesters in the mobile phase were all 479 nm, and that of free astaxanthin, the main saponification product of the astaxanthin esters, was 478 nm.     

Carotenoid Formation by Staphylococcus aureus

The carotenoid pigments of Staphylococcus aureus U-71 were identified as phytoene; zeta-carotene; delta-carotene; phytofluenol; a phytofluenol-like carotenoid, rubixanthin; and three rubixanthin-like carotenoids after extraction, saponification, chromatographic separation, and determination of their absorption spectra. There was no evidence of carotenoid esters or glycoside ethers in the extract before saponification. During the aerobic growth cycle the total carotenoids increased from 45 to 1,000 nmoles per g (dry weight), with the greatest increases in the polar, hydroxylated carotenoids. During the anaerobic growth cycle, the total carotenoids increased from 20 nmoles per g (dry weight) to 80 nmoles per g (dry weight), and only traces of the polar carotenoids were formed. Light had no effect on carotenoid synthesis. About 0.14% of the mevalonate-2-(14)C added to the culture was incorporated into the carotenoids during each bacterial doubling. The total carotenoids did not lose radioactivity when grown in the absence of (14)C for 2.5 bacterial doublings. The total carotenoids did not lose radioactivity when grown in the absence of (14)C for 2.5 bacterial doublings. The incorporation and turnover of (14)C indicated the carotenes were sequentially desaturated and hydroxylated to form the polar carotenoids.     

Spectral characterization of the neuronal pigments of Aplysia juliana.

Spectral analysis at liquid N2 temperature of the circumesophageal ganglia of Aplysia juliana showed that carotenoids and a hemoglobin-like pigment are contained in concentrations of approx. 25 and 3 micronM, respectively, in the whole ganglia. Microspectrophotometrical measurements of Aplysia neurons indicated that the carotenoids reside on lipochondria in a concentration of approx. 38 mM. In addition to lipochondria, two types of pigmented particulate having absorption maxima at about 512 and 525 nm, respectively, were found in the neurons. The neuronal carotenoids consist of violaxanthin, beta-carotene and one minor component; among them the first occupies approx. 77% of total carotenoids. Two principal absorption maxima of the carotenoids, when existing in both ganglial homogenates and Triton X-100 extracts, show a red shift of 10 nm compared with those of free pigments in hexan. The red shift may be interpreted as due to the solvation of the carotenoids by surrounding lipids.     

Detection of chlorophyllide in chlorophyll-free plasma membrane preparations from Anacystis nidulans

Plasma and thylakoid membranes were isolated and purified from the cyanobacterium Anacystis nidulans. Spectrophotometric examination of acetone extracts gave major absorption bands resulting from carotenoids and chlorophyll a in plasma and thylakoid membranes, respectively. Only a very small absorption peak at 663 nm was detected in acetone extracts of plasma membranes which, in contrast to the corresponding peak from thylakoid membranes, could not be extracted into n-hexane; methanol, on the other hand, was effective with both plasma and thylakoid membranes. Aqueous membrane suspensions excited at 435 nm gave strong fluorescence emission at 662 nm for plasma membranes, but only a very small one for thylakoid membranes which had been adjusted to equal absorbance at 678 nm. Excitation spectra of the 668 nm fluorescence emission peak in acetone extracts of plasma and thylakoid membranes were strikingly different from each other. Finally, high performance liquid chromatography afforded clear-cut preparative separation of the two "chlorophyll-like" pigments in plasma and thylakoid membranes, respectively, and identification by comparison with retention characteristics known from the literature, together with a pure chlorophyll a standard. Our results indicate that the highly fluorescent and polar "chlorophyll-like" pigment in plasma membranes of Anacystis is a chlorophyll precursor, viz. chlorophyllide a.     

Spectral characterization of the neuronal pigments of Aplysia juliana

Spectral analysis at liquid N₂ temperature of the circumesophageal ganglia of Aplysia juliana showed that carotenoids and a hemoglobin-like pigment are contained in concentrations of approx. 25 and 3 μM, respectively, in the whole ganglia. Microspectrophotometrical measurements of Aplysia neurons indicated that the carotenoids reside on lipochondria in a concentration of approx. 38 mM. In addition to lipochondria, two types of pigmented particulate having absorption maxima at about 512 and 525 nm, respectively, were found in the neurons. The neuronal carotenoids consist of violaxanthin, β-carotene and one minor component; among them the first occupies approx. 77% of total carotenoids. Two principal absorption maxima of the carotenoids, when existing in both ganglial homogenates and Triton X-100 extracts, show a red shift of 10 nm compared with those of free pigments in hexan. The red shift may be interpreted as due to the solvation of the carotenoids by surrounding lipids     

光合细菌H3菌株色素分析

H3菌株系由盐田微生物层中分离获得的光合细菌株。具有丰富的天然色素。经活细胞色素光谱吸收峰值测定,色素经有机溶剂提取、硅胶薄板层析、SDS－PAGE电泳等,结果表明H3菌株的主要色素包括细菌叶绿素a、细菌脱镁叶绿素（Bacteriophaeophytin）和三种类胡萝卜素。总胡萝卜素含量占细胞于重的0．6％,胡萝卜素蛋白复合体的分子量约11,000.培养条件的差异对色素形成及相对含量有不同程度的影响。     

一株红假单胞菌的分离及生理特性研究

光合细菌在水处理和水生态修复领域应用前景广阔, 对其生理特性研究具有重要价值。从武汉东湖分离得到一株不产氧光合细菌PUF1, 通过对菌落形态、细胞超微结构、特征吸收光谱以及系统发育等分析, 初步确定为红假单胞菌属(Rhodopseudomonas sp.)紫色非硫光合细菌。PUF1细胞呈直的或稍弯曲的杆状, 长3.05—10.06 μm, 直径0.32—0.68 μm, 具有片层膜结构。PUF1培养物呈深紫红色, 主要色素为细菌叶绿素a (Bchl. a)和类胡萝卜素。初始pH 6.0—8.0, 光照强度500—3000 lx, 稳定期细菌生物量无显著差异, 但培养液pH>8.0会显著抑制PUF1最大光量子产量(F_v/F_m)。试验进一步研究了细菌不同生长阶段粗蛋白含量、ATP酶(ATPase)活性及F_v/F_m的变化规律。结果表明, PUF1不同生长阶段其蛋白含量有所差异, 以稳定期为最高(>60%), 而ATPase活性随培养时间的延长而逐渐降低。此外, PUF1光合作用与其生长状态也有一定的关系, 具体表现为细菌生长周期内F_v/F_m变化规律适用单峰高斯模型, 且以对数期F_v/F_m为最高。研究结果可为光合细菌生理生化特性研究提供重要的参考依据。     

Genus Specific Unusual Carotenoids in Purple Bacteria, <Emphasis Type="Italic">Phaeospirillum</Emphasis> and <Emphasis Type="Italic">Roseospira</Emphasis>: Structures and Biosyntheses

Phototrophic bacteria necessarily contain carotenoids for photosynthesis, and a few phototrophic purple bacteria accumulate unusual carotenoids. The carotenoids in the genera Phaeospirillum and Roseospira were identified using spectroscopic methods. All species of the genus Phaeospirillum contained characteristic polar carotenoids in addition to lycopene and hydroxylycopene (rhodopin); hydroxylycopene glucoside, dihydroxylycopene, and its mono- and/or diglucosides. From the structures of these carotenoids, their accumulation was suggested to be due to absence of CrtD (acyclic carotenoid C-3,4 desaturase) and to possession of glucosyltransferase. Species of the genus Roseospira have been reported to have unusual absorption spectra in acetone extract, and they were found to accumulate 3,4-didehydrorhodopin as a major carotenoid. This may be due to low activity of CrtF (acyclic 1-hydroxycarotenoid methyltransferase). The study concludes in identifying genus specific unusual carotenoids, which is probably due to characteristic nature of some carotenogenesis enzymes.     

Electrochemical classification of gram-negative and gram-positive bacteria

Intestinal bacteria were classified as gram-positive or gram-negative by an electrode system with a basal plane pyrolytic graphite electrode and a porous nitrocellulose membrane filter to trap bacteria. When the potential of the graphite electrode was run in the range of 0 to 1.0 V versus the saturated calomel electrode (SCE), gram-positive bacteria gave peak currents at 0.65 to 0.69 V versus the SCE. The peak potentials of gram-negative bacteria were 0.70 to 0.74 V versus the SCE. Gram-negative bacteria and gram-positive bacteria were also classified based on the ratio of the second peak current to the first peak current when the potential cycle was repeated twice. The numbers of cells on the membrane filter were determined from the peak currents. It was found that the peak currents result from the electrochemical oxidation of coenzyme A in the cells of Escherichia coli and Lactobacillus acidophilus.     

Pigments of Rubrobacter radiotolerans

The highly radioresistant Rubrobacter radiotolerans, contains red pigments. Since the pigments could not be extracted by usual methods, a new method was developed in which the pigments were extracted with organic solvents after addition of 10 N KOH to the intact cells, followed by neutralization. These pigments were also extracted after treatment with achromopeptidase, but not with lysozyme. The extracted pigments separated into two main spots by TLC (48.6% and 22.6%), and were confirmed to be carotenoids by chemical tests. The two major pigments had 13 conjugated double bonds as determined from the main maximum wavelength of the light absorption spectra. Their molecular weights were determined to be 740 and 722 by mass spectrometry. The mass spectra of their TMS-derivatives revealed that they contained four and three tertiary OH groups, respectively. Confirming their identical light and IR spectra, these pigments were determined to be bacterioruberin and monoanhydrobacterioruberin, respectively, the characteristic carotenoids of halophilic bacteria. The existence of these pigments in bacteria other than halobacteria provides interesting new evidence on the distribution of these compounds.     

Action Spectra for Transformation and Fluorescence of Protochlorophyll Holochrome from Bean Leaves

The action spectrum from 232 to 687 nm was determined for the transformation of protochlorophyllide into chlorophyllide a in solutions of protochlorophyll holochrome Fran bean leaves. The whole ultraviolet region is effective. The peaks at 445 and 639 nm have a height ratio of 4.0. Only radiation absorbed in the protochlorophyllide itself is effective in transformation (absorption in aromatic amino acids of the protein and in carotenoids is ineffective). The activation spectra for fluorescence at 643 and 683 nm are measured for the holochrome before and after transformation, as well as the change in absorption spectrum that takes place upon transformation. By combining the various measurements the spectrum of inactive (non-transformable) protochlorophyllide (peak at 440 nm) and the holochromatic chlorophyllide a are derived. In the latter spectrum the peaks at 419 and 435 nm are of about the same height.     

Construction and characterization of genetically modified synechocystis sp. PCC 6803 photosystem II core complexes containing carotenoids with shorter pi-conjugation than beta-carotene

Beta-carotene has been identified as an intermediate in a secondary electron transfer pathway that oxidizes Chl(Z) and cytochrome b(559) in Photosystem II (PS II) when normal tyrosine oxidation is blocked. To test the redox function of carotenoids in this pathway, we replaced the zeta-carotene desaturase gene (zds) or both the zds and phytoene desaturase (pds) genes of Synechocystis sp. PCC 6803 with the phytoene desaturase gene (crtI) of Rhodobacter capsulatus, producing carotenoids with shorter conjugated pi-electron systems and higher reduction potentials than beta-carotene. The PS II core complexes of both mutant strains contain approximately the same number of chlorophylls and carotenoids as the wild type but have replaced beta-carotene (11 double bonds), with neurosporene (9 conjugated double bonds) and beta-zeacarotene (9 conjugated double bonds and 1 beta-ionylidene ring). The presence of the ring appears necessary for PS II assembly. Visible and near-infrared spectroscopy were used to examine the light-induced formation of chlorophyll and carotenoid radical cations in the mutant PS II core complexes at temperatures from 20 to 160 K. At 20 K, a carotenoid cation radical is formed having an absorption maximum at 898 nm, an 85 nm blue shift relative to the beta-carotene radical cation peak in the WT, and consistent with the formation of the cation radical of a carotenoid with 9 conjugated double bonds. The ratio of Chl(+)/Car(+) is higher in the mutant core complexes, consistent with the higher reduction potential for Car(+). As the temperature increases, other carotenoids become accessible to oxidation by P(680)(+).     

Drug Absorption Efficiency in Caenorhbditis elegans Delivered by Different Methods

Background

Caenorhbditis elegans has being vigorously used as a model organism in many research fields and often accompanied by administrating with various drugs. The methods of delivering drugs to worms are varied from one study to another, which make difficult in comparing results between studies.

Methodology/Principal Findings

We evaluated the drug absorption efficiency in C. elegans using five frequently used methods with resveratrol with low aqueous solubility and water-soluble 5-Fluoro-2′-deoxyuridine (FUDR) as positive compounds. The drugs were either applied to the LB medium with bacteria OP50, before spreading onto Nematode Growth Medium (NGM) plates (LB medium method), or to the NGM with live (NGM live method) or dead bacteria (NGM dead method), or spotting the drug solution to the surface of plates directly (spot dead method), or growing the worms in liquid medium (liquid growing method). The concentration of resveratrol and FUDR increased gradually within C. elegans and reached the highest during 12 hours to one day and then decreased slowly. At the same time point, the higher the drug concentration, the higher the metabolism rate. The drug concentrations in worms fed with dead bacteria were higher than with live bacteria at the same time point. Consistently, the drug concentration in medium with live bacteria decreased much faster than in medium with dead bacteria, reach to about half of the original concentration within 12 hours.

Conclusion

Resveratrol with low aqueous solubility and water-soluble FUDR have the same absorption and metabolism pattern. The drug metabolism rate in worms was both dosage and time dependent. NGM dead method and liquid growing method achieved the best absorption efficiency in worms. The drug concentration within worms was comparable with that in mice, providing a bridge for dose translation from worms to mammals.     

Mechanisms involved in the intestinal absorption of dietary vitamin A and provitamin A carotenoids

Vitamin A is an essential nutrient for humans and is converted to the visual chromophore, 11-cis-retinal, and to the hormone, retinoic acid. Vitamin A in animal-derived foods is found as long chain acyl esters of retinol and these are digested to free fatty acids and retinol before uptake by the intestinal mucosal cell. The retinol is then reesterified to retinyl esters for incorporation into chlylomicrons and absorbed via the lymphatics or effluxed into the portal circulation facilitated by the lipid transporter, ABCA1. Provitamin A carotenoids such as β-carotene are found in plant-derived foods. These and other carotenoids are transported into the mucosal cell by scavenger receptor class B type I (SR-BI). Provitamin A carotenoids are partly converted to retinol by oxygenase and reductase enzymes and the retinol so produced is available for absorption via the two pathways described above. The efficiency of vitamin A and carotenoid intestinal absorption is determined by the regulation of a number of proteins involved in the process. Polymorphisms in genes for these proteins lead to individual variability in the metabolism and transport of vitamin A and carotenoids. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.     

Carotenoids and throat pouch coloration in the great frigatebird (Fregata minor)

Carotenoid pigments are a common source of red, orange, and yellow coloration in vertebrates. Animals cannot manufacture carotenoids and therefore must obtain them in their diet to produce carotenoid-based coloration. Male great frigatebirds (Fregata minor) display a bright red inflated gular pouch as part of their elaborate courtship display. The basis of this coloration until now has not been investigated. Using high-performance liquid chromatography (HPLC), we investigated the types and concentrations of carotenoids that great frigatebirds circulate in their plasma and whether male gular pouch coloration was carotenoid-based. Great frigatebird plasma collected during the breeding season contained three carotenoid pigments in dilute concentrations-tunaxanthin, zeaxanthin, and astaxanthin-with astaxanthin accounting for nearly 85% of the carotenoids present. Astaxanthin was the only carotenoid present in gular pouch tissue, but the concentration is the highest reported for any carotenoid-pigmented avian tissue. Throat pouch reflectance curves were measured with a UV-VIS spectrophotometer, revealing a complex pattern of one UV peak (approx. 360 nm), two absorption valleys (approx. 542 and 577 nm), followed by a plateau at approx 630 nm. The reflectance curve suggests a role for additional pigments, in particular hemoglobin, in the production of color in this ornament.     

Carotenoid composition, concentrations, and relationships in various human organs

The carotenoid content of 10 different organs obtained at autopsy from 16 humans was determined using a high-performance liquid chromatography assay. The same qualitative pattern of carotenoids found in serum was found for all the tissues, although there were important quantitative differences in the different carotenoids between organs. The median levels of zeaxanthins, lycopene and beta-carotene varied disproportionately between organs; similar levels of one carotenoid for two organs would not predict similar levels of another carotenoid for the same organs. Similarly, there was not a consistent relationship between all the carotenoids for a given organ. The uneven but wide tissue distribution of most dietary carotenoids may indicate an active biological role for these compounds.     

Carotenoid-induced cooperative formation of bacterial photosynthetic LH1 complex

A simple reconstitution technique has been developed and then applied to prepare a series of light-harvesting antenna 1 (LH1) complexes with a programmed carotenoid composition, not available from native photosynthetic membranes. The complexes were reconstituted with different C(40) carotenoids, having two structural parameters variable: the functional side groups and the number of conjugated C-C double bonds, systematically increasing from 9 to 13. The complexes, differing only in the type of carotenoid, bound to an otherwise identical bacteriochlorophyll-polypeptide matrix, can serve as a unique model system in which the relationship between the carotenoid character and the functioning of pigment-protein complexes can be investigated. The reconstituted LH1 complexes resemble the native antenna, isolated from wild-type Rhodospirillum rubrum, but their coloration is entirely determined by carotenoid. Along with the increase in its conjugation size, the carotenoid absorption transitions gradually shift to the red. Thus, the extension of the conjugation size of the antenna carotenoids provides a mechanism for the spectral tuning of light harvesting in the visible part of the spectrum. The carotenoids in the reconstitution system promote the LH1 formation and seem to bind and transfer the excitation energy specifically only to a species with characteristically red-shifted absorption and emission maxima, apparently, due to a cooperative effect. Monitoring the LH1 formation by steady-state absorption and fluorescence spectroscopies reveals that in the presence of carotenoids it proceeds without spectrally resolved intermediates, leading directly to B880. The effect of the carotenoid is enhanced when the pigment contains the hydroxy or methoxy side groups, implying that, in parallel to hydrophobic interactions and pi-pi stacking, other interactions are also involved in the formation and stabilization of LH1.     

Effects of Carotenoid Inhibition on the Photosynthetic RC–LH1 Complex in Purple Sulphur Bacterium Thiorhodospira sibirica

Core complexes (LH1–RC) were isolated using preparative gel electrophoresis from photosynthetic membranes of the purple bacterium, Thiorhodospira sibirica, grown in the absence or presence of the carotenoid biosynthesis inhibitor, diphenylamine. The biosynthesis of carotenoids is affected by diphenylamine both quantitavely and qualitatively: after inhibition, the level of carotenoids in core complexes reaches only 10% of the normal content, as analyzed by HPLC and absorption spectroscopy. The normally grown bacterium biosynthesizes spirilloxanthin, rhodopin, anhydrorhodovibrin and lycopene, whereas after inhibition only neurosporene, ζ-carotene and their derivatives are found in the complexes. There is no concomitant accumulation of appreciable amounts of colorless carotenoid precursors. Interestingly, the main absorption band of the core light harvesting complex isolated from carotenoid-inhibited cells, shows a red shift to 889 nm, instead of a blue shift observed in many carotenoid-deficient species of purple photosynthetic bacteria. The stability of isolated core complexes against n-octyl-β-D-glucopyranoside clearly depends on the presence of carotenoids. Subcomplexes resulting from the detergent treatment, were characterized by non-denaturating gel electrophoresis combined with in situ absorption spectroscopy. Core complexes with the native carotenoid complement dissociate into three subcomplexes: (a) LH1 complexes partially depleted of carotenoids, with an unusual spectrum in the NIR region (λ_max = 791, 818, 847 and 875 nm), (b) reaction centers associated with fragments of LH1, (c) small amounts of a carotenoidless B820 subcomplex. The core complex from the carotenoid-deficient bacterium is much less stable and yields only the two sub-complexes (b) and (c). We conclude that carotenoids contribute critically to stability and interactions of the core complexes with detergents.     

Cloning and sequencing of the histidine decarboxylase genes of gram-negative,histamine-producing bacteria and their application in detection and identification of these organisms in fish

The use of molecular tools for early and rapid detection of gram-negative histamine-producing bacteria is important for preventing the accumulation of histamine in fish products. To date, no molecular detection or identification system for gram-negative histamine-producing bacteria has been developed. A molecular method that allows the rapid detection of gram-negative histamine producers by PCR and simultaneous differentiation by single-strand conformation polymorphism (SSCP) analysis using the amplification product of the histidine decarboxylase genes (hdc) was developed. A collection of 37 strains of histamine-producing bacteria (8 reference strains from culture collections and 29 isolates from fish) and 470 strains of non-histamine-producing bacteria isolated from fish were tested. Histamine production of bacteria was determined by paper chromatography and confirmed by high-performance liquid chromatography. Among 37 strains of histamine-producing bacteria, all histidine-decarboxylating gram-negative bacteria produced a PCR product, except for a strain of Citrobacter braakii. In contrast, none of the non-histamine-producing strains (470 strains) produced an amplification product. Specificity of the amplification was further confirmed by sequencing the 0.7-kbp amplification product. A phylogenetic tree of the isolates constructed using newly determined sequences of partial hdc was similar to the phylogenetic tree generated from 16S ribosomal DNA sequences. Histamine accumulation occurred when PCR amplification of hdc was positive in all of fish samples tested and the presence of powerful histamine producers was confirmed by subsequent SSCP identification. The potential application of the PCR-SSCP method as a rapid monitoring tool is discussed.     

固氮红细菌(Rhodobacter azotoformans) 423 nm特征吸收峰成因与定位

【背景】在不产氧光合细菌中,因420-425nm特征峰位于类胡萝卜素(Carotenoid,Car)吸收区域,通常被认为是由Car积累引起,但固氮红细菌R7菌株呈现的423 nm特征峰不具备Car三指峰特征。【目的】阐明R7菌株423 nm特征吸收峰形成的物质基础及胞内定位。【方法】采用吸收光谱、薄层层析、高效液相色谱、质谱、超速离心和离子交换层析等方法阐明423 nm吸收峰形成原因。【结果】谷氨酸钠明显促进R7菌株活细胞呈现423 nm特征峰,色素提取液中该峰蓝移至415 nm,但其生长、细菌叶绿素(Bacteriochlorophyll,BChl)和Car含量大幅度降低,而添加酵母提取物则反之。色素组成分析表明,在检测到的色素成分中,只有镁卟啉单甲基酯Ⅸ (Magnesium Protoporphyrin Ⅸ Monomethylester,MPE)呈现415 nm特征吸收峰。MPE可定位于光合膜上并呈现出423 nm特征峰。对色素蛋白复合体(Pigment Protein Complex,PPC)的研究显示,添加谷氨酸和酵母提取物的菌体细胞虽然都检测到3种PPC组分[2个外周捕光复合体(Peripheral Light Harvesting Complex 2,LH2)和1个光反应中心(Reaction Center,RC)],但源自谷氨酸菌体细胞的RC和1个LH2则呈现423 nm特征吸收峰,表明R7菌株可产生2种不同类型的LH2,且MPE可定位于一种LH2和RC。【结论】R7菌株所呈现的423 nm特征峰不是由Car积累所致,而是由MPE积累所形成,且能与LH2和RC结合定位于光合膜上。MPE是BChl合成的中间产物,其合成受严格调控,不容易获得。MPE代谢调控的深入研究可为光合作用光氧化损伤与保护机理增添新内容。