陆地革菌的化学成分研究

从陆地革菌(Thelephora terrestris)子实体中分离得到9个已知化合物,经波谱学分析鉴定为:(22E,24R)-麦角甾-7,22-二烯-3β -醇 (1),(22E, 24R)-麦角甾-7, 22-二烯-3β ,5α,6β -三醇 (2),(22E,24R)-麦角甾-4,6,8(14),22-四烯-3-酮 (3),24-亚甲基羊毛甾-8-烯-3β -醇 (4),熊果酸 (5),木栓酮 (6),cerebroside B (7),(2S,3S,4R,2'R)-2-(2'-羟基二十二碳酰氨基)-十八碳烷-1,3,4-三醇 (8),(2S,3S,4R,2'R)-2-(2'-羟基二十三碳酰氨基)-十八碳烷-1,3,4-三醇 (9)。     

白木香果实化学成分研究

运用柱色谱技术从白木香(Aquilaria sinensis (Lour.) Gilg)果实中分离得到7个化合物,经波谱解析和理化性质分别鉴定为: 3-吲哚甲酸(1)、6-羟基-2-[2-(4-羟基苯基)乙基]色原酮(2)、芫花素(3)、4', 5-二羟基-3',7-二甲氧基黄酮(4)、洋芹素-7,4'-二甲醚(5)、 β-谷甾醇(6)和胡萝卜苷(7)。其中化合物1为首次从瑞香科沉香属植物中分离得到。     

Structure and thermal stability of pyruvated carrageenans from the red alga Coccotylus truncatus

The composition, structure, and thermal stability of carrageenans from unattached Coccotylus truncatus (the Baltic Sea, Estonia) were investigated. The complex polysaccharide was characterized by ¹³C NMR and FTIR spectroscopy, ICP-OES and gel permeation chromatography methods. The main components of C. truncatus galactan are 3,6-anhydro-α-d-galactose-2-sulfate (30 ± 1.5%) and β-d-galactose-4-sulfate (45.3%), indicating a ι-carrageenan backbone. As the minor components, α-d-galactose-2,6-disulfate (12 ± 2%) from ν-carrageenan and 4′,6′-pyruvated β-d-galactopyranosyl residues (1.4%) from pyruvated α-carrageenan are found to be present, latter being responsible for the undersulfated nature of the galactan. The native polysaccharide with the average molecular weight of about 1500 kDa is highly susceptible to thermal degradation. The high-temperature treatment of this galactan gives products with 3,6-anhydro-α-d-galactose units predominantly at the reducing end. The carrageenan extraction from C. truncatus gives characteristically low yields (12-17%); weak gelling ability of the polysaccharides from this seaweed species (gel strength 30-40 g/cm²) does not depend significantly on extraction conditions.     

Chemical constituents from the fruits of Sonneratia caseolaris and Sonneratia ovata (Sonneratiaceae)

Nine (1–9) and seven (1–6, 10) compounds were isolated from the fruits of Sonneratia caseolaris and Sonneratia ovata, respectively. Their structures were identified by comparing their MS and NMR data as well as the physical properties with the literature. All the isolated compounds were screened against a rat glioma C-6 cell line using the MTT assay method; only compounds (-)-(R)-nyasol (1), (-)-(R)-4′-O-methylnyasol (2) and maslinic acid (6) were found to show moderate cytotoxic activity. Our findings from these two kinds of fruits can be used as a foundation for further chemotaxonomic studies on Sonneratia species. The nor-lignans (1, 2) and 6H-benzo[b,d]pyran-6-one derivatives (3, 4) were isolated from this genus for the first time, indicating that these two classes of compounds may tentatively be considered as taxonomic markers for Sonneratia genus.     

Chemical variability within the marine sponge Aplysina fulva

Dibromotyrosine-derived metabolites are of common occurrence within marine sponges belonging to the order Verongida. However, previous chemical analysis of crude extracts obtained from samples of the verongid sponge Aplysina fulva collected in Brazil did not provide any dibromotyrosine-derived compounds. In this investigation, five samples of A. fulva from five different locations along the Brazilian coastline and one sample from a temperate reef in the South Atlantic Bight (SAB) (Georgia, USA) were investigated for the presence of bromotyrosine-derived compounds. All six samples collected yielded dibromotyrosine-derived compounds, including a new derivative, named aplysinafulvin, which has been identified by analysis of spectroscopic data. These results confirm previous assumptions that dibromotyrosine-derived metabolites can be considered as chemotaxonomic markers of verongid sponges. The isolation of aplysinafulvin provides additional support for a biogenetic pathway involving an arene oxide intermediate in the biosynthesis of Verongida metabolites. It cannot yet be established if the chemical variability observed among the six samples of A. fulva collected in Brazil and the SAB is the result of different environmental factors, distinct chemical extraction and isolation protocols, or a consequence of hidden genetic diversity within the postulated morphological plasticity of this species.     

Secondary metabolites of Posidonia oceanica (Posidoniaceae)

Posidonia oceanica Delile is an endemic of the Mediterranean Sea. P. oceanica is one of the few marine higher plants of the Mediterranean and plays a significant role in coastal ecosystems of the Mediterranean Sea. In the past, a number of phytochemical investigations with different focus were carried out. The results of these investigations are summarized and appraised here. A total of 51 natural products was reported from P. oceanica, including phenols, phenylmethane derivatives, phenylethane derivatives, phenylpropane derivatives and their esters, chalkones, flavonols, 5α-cholestanes, and cholest-5-enes. Many of the compounds reported for P. oceanica were, however, not detected by appropriate phytochemical methods and some most probably represent artifacts and are no genuine natural products.     

Evolutionarily conserved thermal biology across continents: The North American lizard Plestiodon gilberti (Scincidae) compared to Asian Plestiodon

1.

The lizard genus Plestiodon (Scincidae; formerly Eumeces) is widespread in North America and Asia, but the thermal biology of only a few species has been studied.     

Effect of detergent concentration on the thermal stability of a membrane protein: The case study of bacterial reaction center solubilized by N,N-dimethyldodecylamine-N-oxide

We report on the response of reaction center (RC) from Rhodobacter sphaeroides (an archetype of membrane proteins) to the exposure at high temperature. The RCs have been solubilized in aqueous solution of the detergent N,N-dimethyldodecylamine-N-oxide (LDAO). Changes in the protein conformation have been probed by monitoring the variation in the absorbance of the bacteriochlorine cofactors and modification in the efficiency of energy transfer from tryptophans to cofactors and among the cofactors (through fluorescence measurements). The RC aggregation taking place at high temperature has been investigated by means of dynamic light scattering. Two experimental protocols have been used: (i) isothermal kinetics, in which the time evolution of RC after a sudden increase of the temperature is probed, and (ii) T-scans, in which the RCs are heated at constant rate. The analysis of the results coming from both the experiments indicates that the minimal kinetic scheme requires an equilibrium step and an irreversible process. The irreversible step is characterized by a activation energy of 205 ± 14 kJ/mol and is independent from the detergent concentration. Since the temperature dependence of the aggregation rate was found to obey to the same law, the aggregation process is unfolding-limited. On the other hand, the equilibrium process between the native and a partially unfolded conformations was found to be strongly dependent on the detergent concentration. Increasing the LDAO content from 0.025 to 0.5 wt.% decreases the melting temperature from 49 to 42 °C. This corresponds to a sizeable (22 kJ/mol at 25 °C) destabilization of the native conformation induced by the detergent. The nature of the aggregates formed by the denatured RCs depends on the temperature. For temperature below 60 °C compact aggregates are formed while at 60 °C the clusters are less dense with a scaling relation between mass and size close to that expected for diffusion-limited aggregation. The aggregate final sizes formed at different temperatures indicate the presence of an even number of proteins suggesting that these clusters are formed by aggregation of dimers.     

Improved thermal stability and activity in the cold-adapted lipase B from Candida antarctica following chemical modification with oxidized polysaccharides

In order to improve the thermal stability (t_1/2) and activity of lipase B from cold-adapted Candida antarctica (CALB), amino groups of the enzyme were chemically linked to a range of oxidized polysaccharides using a range of reducing agents. By chemically modifying CALB using 0.1% dextran (250 kDa) at pH 8.6 for 10 days using borane–pyridine complex as reducing agent, increased thermal stability (t_1/2, 168 min at 70°C) and activity (65% higher specific activity) was achieved compared to the unmodified enzyme (t_1/2, 18 min at 70°C). Improvements in thermostability were generally better with high molecular weight polymers such as dextran (40 and 250 kDa) or ficoll (70 and 400 kDa) in comparison to low molecular weight inulin (5 kDa). The shape of the polymer also appeared to be important with elongated, elipsoidal-shaped dextran providing better thermostabilization than spherical-shaped ficoll. Borane–pyridine complex was found to be a good, non-toxic reducing agent for improving thermostability, compared with sodium borohydride and sodium cyanoborohydride. An interesting finding was that, in all cases, specific activity of the modified enzymes increased with a concomitant increase in thermostability. This response defies the general principle of a trade-off between activity and stability, and demonstrates that chemical modification provides new avenues for improving the thermal stability of enzymes from psychrophiles without sacrificing their activity.     

Chemical composition and antimicrobial activity of Cymbopogon citratus and Cymbopogon giganteus essential oils alone and in combination

As part of ongoing research on the chemical composition and the antimicrobial properties of Burkinabe plants essential oils alone and in combination, essential oils (EOs) from leaves of Cymbopogon citratus and Cymbopogon giganteus from Burkina Faso were analyzed by GC-FID and GC-MS. Five constituents, which accounted for 96.3% of the oil, were identified in the EO of C. citratus. Geranial (48.1%), neral (34.6%) and myrcene (11.0%) were the major constituents. For C. giganteus a total of eight compounds were identified which represented 86.0% of the oils extracted. The dominant compounds were limonene (42%) and a set of monoterpene alcohols: trans-p-mentha-1(7),8-dien-2-ol (14.2%), cis-p-mentha-1(7),8-dien-2-ol (12%), trans-p-mentha-2,8-dien-1-ol (5.6%) and cis-p-mentha-2,8-dien-1-ol (5.2%). The EOs were tested against nine bacteria by using disc diffusion and microdilution methods. C. giganteus EO showed antimicrobial effects against all microorganisms tested whereas C. citratus EO failed to inhibit Pseudomonas aeruginosa. The antimicrobial activity of combinations of the two EOs was quantified by the checkerboard method. Combinations of the two EOs exerted synergistic, additive and indifferent antimicrobial effects. Results of the present investigation provide evidence that the combinations of plant EOs could be assessed for synergistic activity in order to reduce their minimum effective dose.     

Mycobiota associated with the ambrosia beetle Scolytodes unipunctatus (Coleoptera: Curculionidae, Scolytinae)

Ambrosia beetles (Coleoptera: Scolytinae) are associated with strictly entomochoric and mutualistic fungi. We studied the mycobiota associated with Scolytodes unipunctatus, ambrosia beetles that infest Cecropia trees in Central America. Isolates were characterized using morphology and rDNA sequences (ITS region, LSU, and SSU rDNA). Four species are described here: Raffaelea scolytodis sp. nov. (Ophiostomatales), Gondwanamyces scolytodis sp. nov., Custingophora cecropiae sp. nov., and Graphium sp. (Microascales). The genus Custingophora is emended to include Knoxdaviesia anamorphs of Gondwanamyces based on uniformity of DNA sequences and phenotype.     

Seagrass light acclimation: 2-DE protein analysis in Posidonia leaves grown in chronic low light conditions

Posidonia oceanica meadows are among the most valuable coastal systems in the Mediterranean basin. They provide nursery and forage areas for many commercially important species, including juvenile mollusc, finfish, and crustaceans. In the Mediterranean Sea, P. oceanica beds have recently suffered from progressive die-offs attributed to lower light availability from elevated water turbidity. In order to understand adaptive low-light responses of this seagrass, we compared the protein expression in plants collected from turbid waters (low-light) with plants collected from pristine-clear waters (high-light). More than 2600 proteins were detected in leaves from both sites. Among them, 26 proteins were differentially expressed in low-light conditions, 12 of which were identified through MASCOT analyses. The remaining 14 proteins, did not receive significant identity scores due to a lack of genomic and proteomic information in available databases. Nevertheless, we observed a 30% down-regulation of RuBisCo large subunit in low-light acclimated leaves. Whereas, enzymes involved in carbohydrate cleavage (1-fructose-bisphosphate aldolase, nucleoside diphosphate kinase, and beta-amylase) were upregulated in low-light conditions. Electron microscopy studies also revealed substantial changes in the stroma lamellae/grana ratios in chloroplasts receiving low-light, possibly as a mechanism for re-establishing optimal PSI/PSII ratios. Furthermore, under low-light conditions, four components of the ubiquitin/mediated proteolysis pathway (26 S proteasome regulatory, proteasome beta type 1, proteasome 7 D beta type, and proteasome alpha 7), and the perchloric acid soluble translation inhibitor protein, were upregulated. This suggests that, in P. oceanica leaves, enhanced protein turnover mediates acclimation to low-light conditions. Also, enzymes involved in defending against cellular stress (superoxide dismutase, pyridoxine, and 2-caffeic-acido-methyl transferase) were differentially expressed in low-light regime. Subsequent aquaria studies involving P. oceanica transplants maintained in low- and high-light conditions, also demonstrate RuBisCo down-regulation and proteasomes upregulation in low-light acclimated plants.     

Septal pore complex morphology in the Agaricomycotina (Basidiomycota) with emphasis on the Cantharellales and Hymenochaetales

The ultrastructure of septa and septum-associated septal pore caps are important taxonomic markers in the Agaricomycotina (Basidiomycota, Fungi). The septal pore caps covering the typical basidiomycetous dolipore septum are divided into three main phenotypically recognized morphotypes: vesicular-tubular (including the vesicular, sacculate, tubular, ampulliform, and globular morphotypes), imperforate, and perforate. Until recently, the septal pore cap-type reflected the higher-order relationships within the Agaricomycotina. However, the new classification of Fungi resulted in many changes including revision of existing and addition of new orders. Therefore, the septal pore cap ultrastructure of more than 325 species as reported in literature was related to this new classification. In addition, the septal pore cap ultrastructures of Rickenella fibula and Cantharellus formosus were examined by transmission electron microscopy. Both fungi have dolipore septa associated with perforate septal pore caps. These results combined with data from the literature show that the septal pore cap-type within orders of the Agaricomycotina is generally monomorphic, except for the Cantharellales and Hymenochaetales.It appears from the fungal phylogeny combined with the septal pore cap ultrastructure that the vesicular-tubular and the imperforate type both may have arisen from endoplasmic reticulum. Thereafter, the imperforate type eventually gave rise to the perforate septal pore cap-type.     

Response of two species of Indo-Pacific corals, Porites cylindrica and Stylophora pistillata, to short-term thermal stress: The host does matter in determining the tolerance of corals to bleaching

The role of both host and dinoflagellate symbionts was investigated in the response of reef-building corals to thermal stress in the light. Replicate coral nubbins of Stylophora pistillata and Porites cylindrica from the GBR were exposed to either 28 °C (control) or 32 °C for 5 days before being returned to an ambient reef temperature (28 °C). S. pistillata was found to contain either Symbiodinium genotype C1 or C8a, while P. cylindrica had type C15 based on ITS genotyping. Analysis of the quantum yield of photosystem (PS) II fluorescence of the symbionts in P. cylindrica showed that light-induced excitation pressure on the C15 Symbiodinium was significantly less, and the steady state quantum yield of PSII fluorescence at noon (ΔF/Fm′) greater, than that measured in C1/C8a Symbiodinium sp. from S. pistillata. Immunoblots of the PS II D1 protein were significantly lower in Symbiodinium from S. pistillata compared to those in P. cylindrica after exposure to thermal stress. The biochemical markers, heat-stress protein (HSP) 70 and superoxide dismutase (SOD), were significantly greater in P. cylindrica before the experiment, and both species of coral increased their biosynthesis of HSP 70 and SOD when exposed to thermal stress. Concentrations of MAAs, glycerol, and lipids were not significantly affected by thermal stress in these experiments, but DNA damage was greater in heat-stressed S. pistillata compared to P. cylindrica. There was minimal coral mucus, which accounts for up to half of the total energy budget of a coral and provides the first layer of defense for invading microbes, produced by S. pistillata after heat stress compared to P. cylindrica. It is concluded that P. cylindrica contains a heat resistant C15 Symbiodinium and critical host proteins are present at higher concentrations than observed for S. pistillata, the combination of which provides greater protection from bleaching conditions of high temperature in the light.     

Chemical modification of Bacillus thuringiensis Cry1Aa toxin single-cysteine mutants reveals the importance of domain I structural elements in the mechanism of pore formation

Bacillus thuringiensis Cry toxins form pores in the apical membrane of insect larval midgut cells. To investigate their mechanism of membrane insertion, mutants in which cysteine replaced individual amino acids located within the pore-forming domain of Cry1Aa were chemically modified with sulfhydryl-specific reagents. The thiol group of cysteine was highly susceptible to oxidation and its reactivity was significantly increased when the toxins were purified under reducing conditions. Addition of a biotin group to the cysteine had little effect on the ability of the toxins to permeabilize Manduca sexta brush border membrane vesicles except for a slight reduction in activity for S252C and a large increase in activity for Y153C. The activity of Y153C was also significantly increased after modification by reagents that added an aromatic or a charged group to the cysteine. When permeability assays were performed in the presence of streptavidin, a large biotin-binding protein, the pore-forming activity of several mutants, including Y153C, where the altered residue is located within the hairpin comprising helices α4 and α5, or in adjacent loops, was significantly reduced. These results support the umbrella model of toxin insertion.