The effects of temperature, pH and sulphide on the community structure of hyperthermophilic streamers in hot springs of northern Thailand

Hyperthermophilic community diversity was assessed in hot-spring streamers along gradients of temperature, pH and sulphide in northern Thailand. A hierarchical sampling design was employed to obtain biomass for culture-independent estimates of 16S rRNA gene-defined prokaryotic diversity. All springs supported several archaeal and bacterial phylotypes, including novel phylotypes that expand the known phylogenetic diversity of terrestrial hyperthermophiles. Diversity appeared significantly greater than that observed for several other geographic locations. Phylotypes belonging to the Aquificales were ubiquitous, further supporting the hypothesis that these chemolithoautotrophs are key members of all hyperthermophilic communities. The chemoorganotrophic genus Thermus was also represented by phylotypes in all springs. Other bacterial taxa represented by environmental sequences included Bacillus, Thermotoga and various unidentified Alphaproteobacteria and Betaproteobacteria. Archaeal phylotypes included the Crenarchaea Desulfurococcus, Pyrobaculum, plus several unidentified hyperthermophilic lineages. A Methanothermococcus-like Euryarchaeon was also identified, with this genus not previously known from streamer communities. A multivariate approach to the analysis of biotic and abiotic data revealed that diversity patterns were best explained by a combination of temperature and sulphide rather than by any other abiotic variable either individually or in combination.     

Synthesis and structure evaluation of a novel cantharimide and its cytotoxicity on SK-Hep-1 hepatoma cells

A remarkable control of the potency of cantharimide is described based on the electronic properties of functional group and it exhibits a relatively less toxic effect to the non-malignant hematological disorder bone marrow cells.     

Effect of self-association on the structural organization of partially folded proteins: inactivated actin

The propensity to associate or aggregate is one of the characteristic properties of many nonnative proteins. The aggregation of proteins is responsible for a number of human diseases and is a significant problem in biotechnology. Despite this, little is currently known about the effect of self-association on the structural properties and conformational stability of partially folded protein molecules. G-actin is shown to form equilibrium unfolding intermediate in the vicinity of 1.5 M guanidinium chloride (GdmCl). Refolding from the GdmCl unfolded state is terminated at the stage of formation of the same intermediate state. An analogous form, known as inactivated actin, can be obtained by heat treatment, or at moderate urea concentration, or by the release of Ca(2+). In all cases actin forms specific associates comprising partially folded protein molecules. The structural properties and conformational stability of inactivated actin were studied over a wide range of protein concentrations, and it was established that the process of self-association is rather specific. We have also shown that inactivated actin, being denatured, is characterized by a relatively rigid microenvironment of aromatic residues and exhibits a considerable limitation in the internal mobility of tryptophans. This means that specific self-association can play an important structure-forming role for the partially folded protein molecules.     

Combinatorial mixture synthesis and biological evaluation of dihydrophenyl triazine antifolates.

The traditional 'one-pot' three component synthesis was adapted successfully for combinatorial mixtures synthesis of dihydrophenyl triazines, which are nonclassical, dihydrofolate reductase (DHFR) inhibitors. Each library was designed to comprise eight reaction mixture pots and in every pot there were three dihydrophenyl triazines. A total of three libraries were synthesized and the final number of compounds harvested was 64. The products precipitated out of the reaction mixture and could be collected easily and cleansed by washing. Solid supports and further purification processes were not required. The reactions were monitored by TLC and a HPLC method was developed to determine the number of products in each pot. All 24 pots were screened for inhibitory activity against the rat liver DHFR. Two pots showed good inhibitory activity and the products in them were individually synthesized, characterized and biologically tested again. One lead compound was identified amongst all the compounds synthesized, and would be further optimized.     

Steel (Sl) mutation in mice: Identification of mutant embryos early in development

A method is described for the reliable identification of Steel mutant mouse embryos in segregating litters as early as Day 11 of gestation based on the color of hair developed in embryonic skin explants.     

A test of ecological and sexual selection hypotheses for geographical variation in coloration and morphology of golden-crowned kinglets (Regulus satrapa)

Aim To date, studies on geographical variation have extensively investigated Bergmann’s rule, yet Gloger’s rule remains infrequently tested, and climatic predictors of variation in carotenoid coloration have not yet been studied. In addition, hypotheses based on sexual selection, which predict that sexual dimorphism should vary with population density and climatic conditions, have received little attention. Our goals were to characterize geographical variation in the coloration and morphology of golden‐crowned kinglets, Regulus satrapa (Passeriformes, Regulidae), and to investigate possible ecological and sexual selection correlates of this variation. Location The entire species range of golden‐crowned kinglets, comprising North and Central America. Methods We collected data from 511 museum specimens, dating from 1847 to 2006, encompassing all five subspecies of golden‐crowned kinglets. We used reflectance spectrometry to quantify crown and mantle coloration, and measured wing‐chord and tarsus length to approximate body size. We obtained geographical and climatic data from online databases, and population density estimates from the literature. Results There were significant subspecific and gender differences in crown coloration and morphology: male kinglets were generally larger and more colourful. Our data revealed mixed support for Bergmann’s rule: tarsus length decreased with increasing latitude, while patterns of variation in wing‐chord and tarsus length showed conflicting results with temperature. Mantle coloration exhibited an opposite trend to that predicted by Gloger’s rule: upper parts became lighter with increasing relative humidity. Crown coloration was negatively correlated with actual evapotranspiration, suggesting that levels of primary productivity are not directly linked to carotenoid abundance. Sexual dimorphism and dichromatism generally increased with greater population density, lower latitudes and elevations, and warmer temperatures, supporting a previously observed pattern of variation in sexual dimorphism. Main conclusions Geographical variation in golden‐crowned kinglets yielded mixed support for Bergmann’s rule and contradicted Gloger’s rule, suggesting that other mechanisms may be operating. Allen’s rule is likely to be a stronger factor influencing tarsus length. Differences in the degree of sexual dimorphism and dichromatism in varying climatic conditions suggest that the intensity of sexual selection differs between habitats. Further studies on geographical variation in sexual dimorphism in various taxa may reveal a previously unrecognized ecogeographical rule.