Cellular location,activity states,and macromolecular organization of glucoamylase in Clostridium thermosaccharolyticum

By application of immunocytochemical techniques at the electron microscope level, glucoamylase was localized to the cell periphery in Clostridium thermosaccharolyticum during and following growth on starch, sucrose or glucose. Levels of immunolabelling were found to be relatively independent of growth substrate and of phase of growth, whereas previous studies had demonstrated strong dependence of glucoamylase activity on growth conditions; previously high levels of glucoamylase activity had been detected after growth on starch (i.e. during the stationary phase after growth) and only very low activities detected during exponential growth and following growth on glucose. The results presented demonstrate that levels of the glucoamylase protein are independent of measurable enzyme activity, and imply that the protein is constitutive. This indicates that the protein can exist in active and inactive states in the cell. By analogy with similar systems, we consider it likely that maturation or activation of newly synthesized glucoamylase occurs during (or following) transport through the cytoplasmic membrane. Electron microscopy of individual protein molecules which had been subjected to negative staining revealed that the enzyme consists of two domains of approximately equal size which are linked by a hinge region.     

利用蛋白质限制性水解法解析大肠杆菌T蛋白的独立结构域

为了解析分支酸变位酶和预苯酸脱氢酶在大肠杆菌T蛋白的定位,根据T蛋白限制性水解结果,分段克隆分支酸变位酶和预苯酸脱氢酶.T蛋白限制性水解结果显示,第93位氨基酸是大片段的N端,分段克隆的1～93 片段测定得到分支酸变位酶活性,96～373片段得到了预苯酸脱氢酶活性.研究表明,大肠杆菌T蛋白由两个独立结构域组成,N端93个氨基酸组成了分支酸变位酶,C端277个氨基酸组成了预苯酸脱氢酶.     

基于滑动窗口的原核转录起始位点计算定位方法

转录起始位点的计算定位是基因转录调控研究的重要内容,但现有方法的识别性能较低。文章作者在已有原核启动子识别算法的基础上,提出了一种基于滑动窗口的原核转录起始位点计算定位方法,通过在合理限定的定位范围内对序列进行滑动扫描,来预测转录起始位点的位置。首先根据窗口序列的交迭组分特征和启动子其它特征分别建立二次判别分类器,用其计算对应位置的似然得分,再利用转录起始位点与翻译起始位点的间隔经验分布信息对似然得分进行修正,最后依照似然得分的分布情况由阈值定位算法确定预测位置。对大肠杆菌真实序列数据的测试结果表明,该定位算法可实现对真实转录起始位点位置的有效预测,与已有算法相比,当敏感性指标同为0.85左右时,特异性指标可从0.20提高至0.65,从而使得定位准确率提高了约20个百分点。     

炭角菌科部分类群的生物地理学研究(英文)

与肉质真菌相比,大多数炭角菌科真菌的子实体结构和质地使其在自然环境中保持长久,不易腐变,这有利于记录该科采集物的分布信息,基于过去长达25年对该科的深厚工作积累,使我们有可能对其进行地理分布的研究。     

植物挥发性物质在蚜虫寄主定位中的作用

本文综述了植物挥发性物质的化学性质、研究方法及其在蚜虫寄主定位中的作用     

三肽囊素(bursin)的鸡、鸭免疫器官组织学定位特征分析(简报)

三肽囊素(bursin)是法氏囊组织提取物中一种非常重要的活性因子,由Audhya T.等在1986年首次报道。近十几年,有关三肽囊素的研究取得了较大的进展,涉及对三肽囊素的生物学活性、组织学定位、功能机制及其应用前景。本研究分别探索了三肽囊素在鸡、鸭免疫器官中的定位,并对其特征进行分析,以期更深入理解三肽囊素的存在及其生物学意义。鸡用近交系(CB系),由12、14及20日龄胚、新生雏、1—9周龄鸡,采集法氏囊、法氏囊T细胞区、胸腺、哈德氏腺、脾脏及骨髓。鸭用北京鸭,由新生     

中国生物多样性在线数据处理平台的构建

高质量的生物多样性数据能够为生物多样性的研究与保护提供数据支撑。目前研究人员开发了大量的生物多样性数据处理软件或工具, 包括工作流系统、R语言包、Python语言包和Excel工具等, 但是使用这些软件或工具需要用户安装相应的软件客户端, 并掌握一定的编程语言、软件开发和复杂的Excel公式等知识和技能。为降低用户的学习成本和使用门槛, 本文采用了Browser/Server模式设计技术、Web技术、可视化技术、响应式开发技术、网络爬虫技术、数据处理技术和Solr智能检索技术等, 针对不同维度的生物多样性数据设计和开发了相应的数据处理模块, 构建了中国生物多样性在线数据处理平台(http://dp.iflora.cn/)。该平台能够有效地帮助科研人员对物种名称、地理位置、时间日期和经纬度等数据进行处理, 并提供数据格式转换、数据质量评测和资源统计分析等辅助功能, 帮助科研人员实现零代码和低门槛地处理生物多样性数据, 提供便捷、高效和简单的数据清洗、校正、转换和整合等数据处理渠道, 为生物多样性研究和保护提供信息化技术支持与服务。     

Subcellular pH and predicted pH-dependent features of proteins

A characteristic of two-dimensional proteomics gels is a general bimodal distribution of isoelectric (pI) values. Discussion of this feature has focussed on the balance of acidic and basic ionisable residues, and potential relationships between pI distributions and organism classification or protein subcellular location. Electrostatics calculations on a set of protein structures with known subcellular location show that predicted folded state pI are similar to those calculated from sequence alone, but adjusted according to a general stabilising effect from interactions between ionisable groups. Bimodal distributions dominate both pI and the predicted pH of maximal stability. However, there are significant differences between these features. The average pH of maximal stability generally follows organelle pH. Average pI values are well removed from organelle pH in most subcellular environments, consistent with the view that proteins have evolved to carry (on average) net charge in a given subcellular location, and relevant to discussion of solubility in crowded environments. Correlation of the predicted pH of maximum stability with subcellular pH suggests an evolutionary pressure to adjust folded state interactions according to environment. Finally, our analysis of ionisable group contributions to stability suggests that Golgi proteins have the largest such term, although this dataset is small.