牛病毒性腹泻病毒的成熟和释放

试验中用电镜观察了牛病毒性腹泻病毒ＯｒｅｇｏｎＣ２４Ｖ株在感染新生牛睾丸细胞中的形态发生。成熟的病毒颗粒是直径约为５０ｎｍ的球形颗粒,内含直径约为３０ｎｍ的核心。病毒在宿主细胞的胞质内复制,通过糙面内质网膜出芽成熟。病毒可以通过外排或在细胞死亡后含有病毒颗粒的空泡崩溃而释放到胞外。     

Isolation and characterization of a hepcidin peptide from the head kidney of large yellow croaker, Pseudosciaena crocea

Large yellow croaker (Pseudosciaena crocea) is one of the most important marine cultured fish in China. Acidic extracts of five tissues of large yellow croaker showed strong anti-Vibrio alginolyticus activity. Acidic extract of head kidney tissue was subjected to heat-treatment in boiling water, and solid-phase extraction on Sep-Pak C₁₈ cartridge. It was found that the antibacterial substances were heat stable, and 20% acetonitrile effluent exhibited strong antibacterial activity. Active extract was further applied to Sephadex G-25 gel permeation chromatography and StableBond C₁₈RP-HPLC. An antibacterial peptide with a single peak was obtained. The results of amino acid sequencing and MALDI-TOF MS suggested that the peptide was RCRFCCRCCPRMRGCGICCRF with an observed molecular mass of 2523.2 Da. BLAST searching suggested that the purified antibacterial peptide was the mature peptide section of the hepcidin preproprotein presumed from cDNA of large yellow croaker, thus designated hepcidin-Pl. Hepcidin-P1 exhibited strong antibacterial activity against four marine vibrios.     

草鱼CYP1A和ACT基因cDNA片段的克隆与鉴定

以Trizol法分别提取BNF诱导和对照处理草鱼的肝组织总RNA并合成cDNA第一链,以此为模板利用1对ACT特异性引物和(8条)6对CYP1A简并引物进行扩增。结果显示,引物对F0-R0在对照和诱导草鱼中均扩增得到预期ACTcDNA片段,而引物对F4-R4在诱导草鱼中获得预期CYP1A cDNA产物。这两个cDNA片段分别进行克隆、测序和比对,BLAST结果表明草鱼ACTcDNA片段(800 bp)与GenBank中ACT基因(登录号M25013)同源性为99.1%,推导氨基酸序列同源性为99.2%;草鱼CYP1A cDNA片段(439 bp)与鲤鱼同源性最高,为92.5%,推导氨基酸同源性为96.6%。上述序列提交GenBank,获得登录号分别为DQ211096和DQ211095。通过Mega 3.1软件的Neighbor-joining程序对CYP基因的部分cDNA序列和氨基酸序列进行比对分析并绘制进化树,根据CYP1A部分蛋白的系统发育关系,在进化上可以将参与比对的真骨鱼划分为4个主要的分支。     

Theoretical investigation of direct amination of β-ketoesters catalyzed by copper(II)-bisoxazoline(BOX)

The mechanism of the direct amination of β-keto esters catalyzed by copper(II)-bisoxazoline has been studied by means of density functional theory of B3LYP method. The computational results support the present mechanism, which involves (i) the generation of the enol from β-keto esters, which coordinates to copper(II)-bisoxazoline. The coordination step appears to be fast, exothermic, and irreversible. (ii) The formation of the σ(N-C) bond via a six-membered ring transition state after azo dicarboxylate coordination with the chiral catalyst. This step is chirality-control step. (iii) Intramolecular hydrogen migration generates a catalyst-product complex, which can finally yield product. The hydrogen shift is the rate-determining step, which affords the experimentally observed (R)-product. The stereochemical predictions have been rationalized in terms of steric repulsions, showing good agreement with experimental data. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

乌头产吲哚乙酸内生细菌遗传多样性、抗逆性及其对水稻幼苗生长的影响

[目的]探究乌头产吲咮乙酸(IAA)内生细菌的遗传多样性、溶磷解钾能力、抗逆能力及其对水稻幼苗生长的影响,为道地产区乌头产业可持续发展提供科技支撑.[方法]从健康乌头植株分离可培养内生细菌,采用Salkowski比色法测定内生细菌产IAA能力,16S rDNA限制性片段长度多样性(16S rDNA-RFLP)及16S ...     

根瘤菌中甲硫氨酸亚砜还原酶底物蛋白的筛选与相互作用验证

根瘤菌在侵染豆科植物过程中会受到活性氧的氧化胁迫,含甲硫氨酸的蛋白质易被氧化成甲硫氨酸亚砜导致蛋白结构和功能改变,甲硫氨酸亚砜还原酶(methionine sulfoxide reductases, Msrs)能将甲硫氨酸亚砜还原成甲硫氨酸,恢复蛋白的结构和功能。前期在华癸中慢生根瘤菌(Mesorhizobium huakuii) 7653R基因组中发现有4个Msrs和抗氧化压力密切相关,但其作用机制仍不清楚。【目的】通过筛选4个Msrs的相互作用底物,为阐明4个Msrs在M. huakuii 7653R中的作用机制提供证据。【方法】按照甲硫氨酸含量由高到低统计M. huakuii 7653R中所有蛋白的分布情况;利用蛋白互作网站预测获得4个Msrs的候选互作底物,将预测互作底物进行功能注释基因本体(gene ontology, GO)分析和京都基因和基因组百科全书(Kyoto encyclopedia of genes and genomes, KEGG)代谢通路分析;通过细菌双杂交初步验证它们之间的相互作用。【结果】甲硫氨酸含量百分数分布基本呈正态分布形式,位于中间百分数的蛋白最多,位于两边的蛋白较少;筛选获得有6个抗氧化酶和6个转录调控因子是4个Msrs的候选互作底物;细菌双杂交显示,有2个抗氧化酶和5个转录调控因子确实和4个Msrs存在不同程度的相互作用。【结论】为阐明Msrs在根瘤菌M. huakuii 7653R中抵抗氧化压力的作用机制提供了证据,为揭示根瘤菌抵抗活性氧提供了新的思路和方向。     

样本量与研究范围变化对MaxEnt模型准确度的影响——以黑白仰鼻猴为例

MaxEnt模型是过去几年最为流行的物种分布预测模型之一。针对一些濒危物种、入侵种和模拟数据的研究表明,MaxEnt模型均能在小样本的分布数据下得到较准确的预测结果。此外,研究范围的变化也会影响MaxEnt模型的构建。 然而,基于动物的实际分布数据来评估MaxEnt模型的研究甚少。 我们以黑白仰鼻猴 (Rhinopithecus bieti)为例,以11个猴群的分布数据为训练数据（样本量从1到10个猴群）,在不同研究范围内构建MaxEnt模型,通过其它5个的猴群分布数据验证,分析样本量和研究范围变化对模型准确度产生的影响。 结果表明,随样本量和研究范围增大,MaxEnt模型准确度及稳定性都有增加。 此外,研究范围变化对模型准确度有一定影响。 应用Maxent进行物种分布预测时,训练数据应尽可能涵盖该物种可能出现的全部环境梯度。构建模型所需的背景数据点选择,应与建模使用的物种出现点形成有效对照。