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931.
Ricardo Sposina Sobral Teixeira Félix Gonçalves Siqueira Marcelo Valle de Souza Edivaldo Ximenes Ferreira Filho Elba Pinto da Silva Bon 《Journal of industrial microbiology & biotechnology》2010,37(10):1041-1051
This study presents data on the production, purification, and properties of a thermostable β-xylanase produced by an Aspergillus awamori 2B.361 U2/1 submerged culture using wheat bran as carbon source. Fractionation of the culture filtrate by membrane ultrafiltration
followed by Sephacryl S-200 and Q-Sepharose chromatography allowed for the isolation of a homogeneous xylanase (PXII-1), which
was 32.87 kDa according to MS analysis. The enzyme-specific activity towards soluble oat spelt xylan, which was found to be
490 IU/mg under optimum reaction conditions (50°C and pH 5.0–5.5), was 17-fold higher than that measured in the culture supernatant.
Xylan reaction products were identified as xylobiose, xylotriose, and xylotetraose. K
m values (mg ml−1) for soluble oat spelt and birchwood xylan were 11.8 and 9.45, respectively. Although PXII-1 showed 85% activity retention
upon incubation at 50°C and pH 5.0 for 20 days, incubation at pH 7.0 resulted in 50% activity loss within 3 days. PXII-1 stability
at pH 7.0 was improved in the presence of 20 mM cysteine, which allowed for 85% activity retention for 25 days. This study
on the production in high yields of a remarkably thermostable xylanase is of significance due to the central role that this
class of biocatalyst shares, along with cellulases, for the much needed enzymatic hydrolysis of biomass. Furthermore, stable
xylanases are important for the manufacture of paper, animal feed, and xylooligosaccharides. 相似文献
932.
c-Myc overexpression and endocrine resistance in breast cancer 总被引:5,自引:0,他引:5
933.
Reyes-Prieto A Hackett JD Soares MB Bonaldo MF Bhattacharya D 《Current biology : CB》2006,16(23):2320-2325
A single cyanobacterial primary endosymbiosis that occurred approximately 1.5 billion years ago is believed to have given rise to the plastid in the common ancestor of the Plantae or Archaeplastida--the eukaryotic supergroup comprising red, green (including land plants), and glaucophyte algae. Critical to plastid establishment was the transfer of endosymbiont genes to the host nucleus (i.e., endosymbiotic gene transfer [EGT]). It has been postulated that plastid-derived EGT played a significant role in plant nuclear-genome evolution, with 18% (or 4,500) of all nuclear genes in Arabidopsis thaliana having a cyanobacterial origin with about one-half of these recruited for nonplastid functions. Here, we determine whether the level of cyanobacterial gene recruitment proposed for Arabidopsis is of the same magnitude in the algal sisters of plants by analyzing expressed-sequence tag (EST) data from the glaucophyte alga Cyanophora paradoxa. Bioinformatic analysis of 3,576 Cyanophora nuclear genes shows that 10.8% of these with significant database hits are of cyanobacterial origin and one-ninth of these have nonplastid functions. Our data indicate that unlike plants, early-diverging algal groups appear to retain a smaller number of endosymbiont genes in their nucleus, with only a minor proportion of these recruited for nonplastid functions. 相似文献
934.
Teixeira CP Hirsch A Perini H Young RJ 《Proceedings. Biological sciences / The Royal Society》2006,273(1589):1007-1012
We report the development of a new quantitative method of assessing the effects of anthropogenic impacts on living beings; this method allows us to assess actual impacts and to travel backwards in time to assess impacts. In this method, we have crossed data on fluctuating asymmetry (FA, a measure of environmental or genetic stress), using Didelphis albiventris as a model, with geographical information systems data relating to environmental composition. Our results show that more impacted environments resulted in statistically higher levels of FA. Our method appears to be a useful and flexible conservation tool for assessing anthropogenic impacts. 相似文献
935.
Cossenza M Cadilhe DV Coutinho RN Paes-de-Carvalho R 《Journal of neurochemistry》2006,97(5):1481-1493
The synthesis of nitric oxide (NO) is limited by the intracellular availability of L-arginine. Here we show that stimulation of NMDA receptors promotes an increase of intracellular L-arginine which supports an increase in the production of NO. Although L-[3H]arginine uptake measured in cultured chick retina cells incubated in the presence of cycloheximide (CHX, a protein synthesis inhibitor) was inhibited approximately 75% at equilibrium, quantitative thin-layer chromatography analysis showed that free intracellular L-[3H]arginine was six times higher in CHX-treated than in control cultures. Extracellular L-[3H]citrulline levels increased threefold in CHX-treated groups, an effect blocked by NG-nitro-L-arginine, a NO synthase (NOS) inhibitor. NMDA promoted a 40% increase of free intracellular L-[3H]arginine in control cultures, an effect blocked by the NMDA antagonist 2-amino 5-phosphonovaleric acid. In parallel, NMDA promoted a reduction of 40-50% in the incorporation of 35[S]methionine or L-[3H]arginine into proteins. Western blot analysis revealed that NMDA stimulates the phosphorylation of eukaryotic elongation factor 2 (eEF2, a factor involved in protein translation), an effect inhibited by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK801). In conclusion, we have shown that the stimulation of NMDA receptors promotes an inhibition of protein synthesis and a consequent increase of an intracellular L-arginine pool available for the synthesis of NO. This effect seems to be mediated by activation of eEF2 kinase, a calcium/calmodulin-dependent enzyme which specifically phosphorylates and blocks eEF2. The results raise the possibility that NMDA receptor activation stimulates two different calmodulin-dependent enzymes (eEF2 kinase and NOS) reinforcing local NO production by increasing precursor availability together with NOS catalytic activity. 相似文献
936.
R5 variants of human immunodeficiency virus type 1 preferentially infect CD62L- CD4+ T cells and are potentially resistant to nucleoside reverse transcriptase inhibitors
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937.
Mateos JL Luppi JP Ogorodnikova OB Sineshchekov VA Yanovsky MJ Braslavsky SE Gärtner W Casal JJ 《The Journal of biological chemistry》2006,281(45):34421-34429
Phytochrome A (phyA) is a versatile plant photoreceptor that mediates responses to brief light exposures (very low fluence responses, VLFR) as well as to prolonged irradiation (high irradiance responses, HIR). We identified the phyA-303 mutant allele of Arabidopsis thaliana bearing an R384K substitution in the GAF subdomain of the N-terminal half of phyA. phyA-303 showed reduced phyA spectral activity, almost normal VLFR, and severely impaired HIR. Recombinant N-terminal half oat of PHYA bearing the phyA-303 mutation showed poor incorporation of chromophore in vitro, despite the predicted relatively long distance (>13 A) between the mutation and the closest ring of the chromophore. Fusion proteins bearing the N-terminal domain of oat phyA, beta-glucuronidase, green fluorescent protein, and a nuclear localization signal showed physiological activity in darkness and mediated VLFR but not HIR. At equal protein levels, the phyA-303 mutation caused slightly less activity than the fusions containing the wild-type sequence. Taken together, these studies highlight the role of the N-terminal domain of phyA in signaling and of distant residues of the GAF subdomain in the regulation of phytochrome bilin-lyase activity. 相似文献
938.
Mouse pleurisy induced by carrageenan is used to determine the mechanism of anti-inflammatory action of 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2-H-1,4-benzodiazepin-2 (Ro5-4864). Pre-treatment with Ro5-4864 inhibits different inflammatory parameters, such as neutrophil influx, MPO activity and NO levels in the early phase (4 h), as well as mononuclear cells and ADA activity in the late phase (48 h) of pleurisy. dl-Aminoglutethimide, inhibitor of steroidal synthesis, reverted the effect of Ro5-4864 on these different inflammatory parameters. Our results suggest that anti-inflammatory action of Ro5-4864 may be partly due to its capacity to inhibit leukocyte migration, as well as leukocyte activation and formation of NO by a mechanism dependent on glucocorticoids. 相似文献
939.
In this paper we explore the consequences of long distance dispersal in biological invasion processes through simulations using a recently developed cellular automaton model. We show that long distance dispersal generate characteristic spatial patterns with several stationary scale-invariant properties. In particular, the patterns display a main patch around the focus of spread, with a fractal border structure whose fractal dimension contains information about the main statistical properties of the dispersal mechanism. Our results are in agreement with field data of spread of invaders with long distance dispersal mechanisms. 相似文献
940.
Amos Danielli Noga Porat Marcelo Ehrlich Ady Arie 《Journal of visualized experiments : JoVE》2010,(40)
A magnetic modulation biosensing system (MMB) [1,2] rapidly and homogeneously detected biological targets at low concentrations without any washing or separation step. When the IL-8 target was present, a ''sandwich''-based assay attached magnetic beads with IL-8 capture antibody to streptavidin coupled fluorescent protein via the IL-8 target and a biotinylated IL-8 antibody. The magnetic beads are maneuvered into oscillatory motion by applying an alternating magnetic field gradient through two electromagnetic poles. The fluorescent proteins, which are attached to the magnetic beads are condensed into the detection area and their movement in and out of an orthogonal laser beam produces a periodic fluorescent signal that is demodulated using synchronous detection. The magnetic modulation biosensing system was previously used to detect the coding sequences of the non-structural Ibaraki virus protein 3 (NS3) complementary DNA (cDNA) [2]. The techniques that are demonstrated in this work for external manipulation and condensation of particles may be used for other applications, e.g. delivery of magnetically-coupled drugs in-vivo or enhancing the contrast for in-vivo imaging applications.Download video file.(80M, mp4) 相似文献