Characterisation of a highly stable α-amylase from the halophilic archaeon Haloarcula hispanica

Intracellular and extracellular proteins from halophilic archaea face very saline conditions and must be able to maintain stability and functionality at nearly saturated salt concentrations. Haloarchaeal proteins contain specific adaptations to prevent aggregation and loss of activity in such conditions, but these adaptations usually result in a lack of stability in the absence of salt. Here, we present the characterisation of a secreted -amylase (AmyH) from the halophilic archaeon Haloarcula hispanica. AmyH was shown to be very halophilic but, unusually for a halophilic protein, it retained activity in the absence of salt. Intrinsic fluorescence measurements and activity assays showed that AmyH was very stable in high-salt buffer and even maintained stability upon the addition of urea. Urea-induced denaturation was only achieved in the absence of NaCl, demonstrating clearly that the stability of the protein was salt-dependent. Sequencing of the amyH gene showed an amino acid composition typical of halophilic proteins and, moreover, the presence of a signal peptide containing diagnostic features characteristic of export via the Twin-arginine translocase (Tat). Analysis of the export of AmyH showed that it was translocated post-translationally, most likely in a folded and active conformation, confirming that AmyH is a substrate of the Tat pathway.     

腺嘌呤与氢化可的松大鼠肾阳虚模型造模方法比较

目的比较腺嘌呤诱导与氢化可的松诱导的SD大鼠肾阳虚模型的优劣,从而得到临床症状、生化指标更符合中医“肾阳虚”型的动物模型,以供科研、教学使用。方法雄性SD大鼠100只,随机分成正常组、腺嘌呤造模组及氢化可的松低剂量组、中剂量组、高剂量组各20只,造模成功后检测血肌酐（Scr）、尿素氮（BUN）、尿液中17-羟皮质类固醇（17-OH）和血浆中甲状腺激素（13、T4）、睾丸酮（T）、雌二醇（E2）及模型大鼠骨密度。结果无论从症状主证方面,还是客观指标方面（除骨密度外）,腺嘌呤诱导的SD大鼠肾阳虚型动物模型在生化指标研究方面均优于氢化可的松诱导组。结论腺嘌呤诱导的肾阳虚证SD大鼠模型在症状主证方面及其相关的生化研究方面优于氢化可的松组。     

Studies on bacteria-like particles sampled from the stratosphere

Bacteria-like particles recovered from the stratosphere and deposited on cellulose acetate membranes have been analysed to confirm their bacterial nature. One particle appeared to be attached to an inorganic particle apparently by mucoid material typically produced by bacteria. A filamentous structure, morphologically similar to a fungal hypha, was also observed. EDS analysis showed that the particles were all non-mineral and therefore could be biological in nature. However, the composition of several clumps of nanobacteria-sized particles were found, by SIMS analysis, to be inconsistent with that of bacteria. The results show that it is dangerous to assume that bacteria-like particles seen under scanning electron microscopy are necessarily bacteria.     

Polyploid genome of <Emphasis Type="Italic">Camelina sativa</Emphasis>revealed by isolation of fatty acid synthesis genes

Background  

Camelina sativa, an oilseed crop in the Brassicaceae family, has inspired renewed interest due to its potential for biofuels applications. Little is understood of the nature of the C. sativa genome, however. A study was undertaken to characterize two genes in the fatty acid biosynthesis pathway, fatty acid desaturase (FAD) 2 and fatty acid elongase (FAE) 1, which revealed unexpected complexity in the C. sativa genome.     

Invasive aspergillosis in a "healthy" patient.

A case of invasive aspergillosis complicated by the formation of an aspergilloma is described. The patient, a 48-year-old man, was apparently healthy except for mild alcoholic steatosis of the liver. A review of the literature revealed that 5 of the 14 previously reported cases of invasive aspergillosis in seemingly immunocompetent hosts were associated with liver disease. Immunologic investigation in this case revealed transient cutaneous anergy during the acute illness and normal lymphocyte function. Assessment of polymorphonuclear leukocyte function, however, showed abnormalities of phagocytosis as well as impairment of intracellular bactericidal activity. These abnormalities may have contributed to a relative immunodeficiency. Impairment of immune function may play a role in the pathogenesis of invasive aspergillosis in some apparently healthy patients.     

Onion yield as affected by plant density,nitrogen level and loss of leaf area

Onion (Allium cepa) is an important horticulture crop because of its value as a food with a long shelf life being a relatively non-perishable product. It is very helpful to understand the growth response of the seeded onion crop to conduct appropriate field practices in attaining the highest or optimum yields. A three year field experiment was conducted using a variety of onion Valcatorce INTA, in a randomized block design with five replicates. Treatments were two plant densities and three rates of N application. The bulb growth followed a classical sigmoid curve. During the rapid growing period, the crop had the greatest leaf area (LA) with at least six leaves per plant. Increasing plant density increased yield in kg/ha, but decreased bulb size. Defoliating 40 to 60% of the LA had a significant impact on bulb production only at early growth stages. Late in the growing period, the remaining LA was apparently large enough for producing sufficient amounts of metabolites to feed new leaves, increasing their photosynthesis efficiency for the benefit of bulb production.     

Molecular dynamics of synthetic leucine-serine ion channels in a phospholipid membrane

Molecular dynamics calculations were carried out on models of two synthetic leucine-serine ion channels: a tetrameric bundle with sequence (LSLLLSL)(3)NH(2) and a hexameric bundle with sequence (LSSLLSL)(3)NH(2). Each protein bundle is inserted in a palmitoyloleoylphosphatidylcholine bilayer membrane and solvated by simple point charge water molecules inside the pore and at both mouths. Both systems appear to be stable in the absence of an electric field during the 4 ns of molecular dynamics simulation. The water motion in the narrow pore of the four-helix bundle is highly restricted and may provide suitable conditions for proton transfer via a water wire mechanism. In the wider hexameric pore, the water diffuses much more slowly than in bulk but is still mobile. This, along with the dimensions of the pore, supports the observation that this peptide is selective for monovalent cations. Reasonable agreement of predicted conductances with experimentally determined values lends support to the validity of the simulations.     

Inferring functional modules of protein families with probabilistic topic models

Background  

Genome and metagenome studies have identified thousands of protein families whose functions are poorly understood and for which techniques for functional characterization provide only partial information. For such proteins, the genome context can give further information about their functional context.