Exploration of the binding mode of α/β-type small acid soluble proteins (SASPs) with DNA

The α/β-type small acid soluble proteins (SASPs) are a major factor in protecting the spores from being killed in bacteria. In this article, we perform a systematic phylogenetic analysis of the α/β-type SASP in the genus of Geobacillus, which indicates that the whole family can be divided into three groups. We choose one protein from each group as a representative and construct the tertiary structure of these proteins. In order to explore the mechanism of protecting DNA from damage, 15 ns molecular dynamics simulation for the four complexes of Gsy3 with DNA are performed. The sequence alignment, model structure and binding energy analysis indicate that the helix2 region of SASPs is more conserved and plays a more crucial role in protecting DNA. Pairwise decomposition of residue interaction energies calculation demonstrate that amino acids of Asn10, Lys24, Asn49, Ile52, Ile56, Thr57, Lys58, Arg59 and Val61 take major effect in the binding interaction. The differences of energy contribution of the amino acids between different complexes make us conclude that the protein structure conformation has a slight change upon more proteins binding to DNA and consequently there occur protein-protein cooperation interactions.     

心房颤动患者血清脑钠肽水平变化的临床研究

目的：探讨患者心房颤动（房颤,AF）发作时对血清脑钠肽水平的影响。方法：选择阵发性房颤组、持续性房颤组、对照组（窦性心律）患者各30例,观察各组血清脑钠肽水平;并对阵发性房颤组中心室率≤100 beats/min与心室率〉100 beats/min的患者进行亚组分析;观察阵发性房颤组复律后24 h和30 d血清脑钠肽水平。结果：阵发性房颤组和持续性房颤组血清脑钠肽水平明显高于对照组（P〈0.01）,房颤复律后血清脑钠肽水平很快下降。结论：血清脑钠肽水平在房颤发作时明显升高,血清脑钠肽水平的升高与房颤的发作有关。     

中国"三江并流"纵谷地蚤类丰富度与区系沿纬度梯度的水平分布格局

为探讨横断山区蚤类物种丰富度与区系沿纬度梯度变化的基本规律以及影响它们分布的主要生态因子,作者就云南西部横断山区21o-28oN的8个纬度梯度带目前所知分布的9科45属153种(亚种)蚤类的水平分布资料进行了综合整理和统计分析。结果表明:(1)这一区域蚤类科、属、种丰富度,特有种丰富度和特有度,以及东洋界和古北界区系成分物种丰富度沿纬度梯度的变化,都呈现了随纬度增加先增高后降低的单峰分布格局,最大峰值出现在25o-27oN之间,研究认为,形成物种密度高峰的主要因素是两大区系分界线和交错区的边缘效应;(2)东洋和古北两大区系成分构成比的水平分布格局截然不同,前者随纬度的增加递减,后者则随纬度的增加呈递增的趋势,两区系成分过渡或交错区的跨度在23o-29oN之间,并在25o-27oN形成交汇和分异的中心;(3)聚类分析结果表明,横断山8个纬度梯度带的蚤类总体上归为3个主要地域区系类型,反映出纬度、地理气候环境等因素对蚤类区系及物种分布的影响,以及蚤类区系和物种组成沿纬度梯度的水平分布格局与地理和气候环境的统一性;(4)蚤类的属、种β多样性沿纬度梯度的水平分布基本呈现双峰格局,峰值反映出蚤类的组成及分布在不同纬度梯度、气候带之间的过渡与转变,说明β多样性的水平分布格局与纬度梯度的气候、环境变化程度的关系密切,以及过渡区的边缘效应对两区系物种丰富度高峰的形成具有重要影响;(5)横断山区蚤类物种丰富度与区系的水平分布与垂直分布的规律和格局基本相同,显示了具有同源性的水平地带性与垂直地带性对蚤类空间分布格局所产生的类似影响,证实了横断山区蚤类物种丰富度与区系的水平分布格局理应出现近似于它们垂直分布的一般规律与格局的推论;(6)横断山25o-27oN的区域形成了两大区系物种交汇和分异的中心,由于边缘效应和复杂的地理景观,这里蚤类科、属、种、特有种都具有较高多样性,据此作者推断,这里可能是我国横断山区多物种保存、分布和分化的核心区。     

siRNA在治疗学中的应用

小干扰RNA（small interfering RNA,siRNA）是外源性双链RNA（double strand RNA,dsRNA）的加工产物,在细胞内能介导RNA干扰（RNA interference,RNAi）效应,识别特异性mRNA,沉默同源基因表达。其特异性和高效性显示出很高的实用价值,siRNA已成为许多疾病潜在的治疗手段。对于siRNA的应用,尽管还需要在减少非特异反应,发掘高效递药载体,应对新的基因变异等方面进行深入研究,但其可望在抗病毒、神经系统疾病和肿瘤治疗等许多领域发挥治疗作用。     

Characterization of a novel C-type lectin-like gene, LSECtin: demonstration of carbohydrate binding and expression in sinusoidal endothelial cells of liver and lymph node

A new C-type lectin-like gene encodes 293 amino acids and maps to chromosome 19p13.3 adjacent to the previously described C-type lectin genes, CD23, dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN), and DC-SIGN-related protein (DC-SIGNR). The four genes form a tight cluster in an insert size of 105 kb and have analogous genomic structures. The new C-type lectin-like molecule, designated liver and lymph node sinusoidal endothelial cell C-type lectin (LSECtin), is a type II integral membrane protein of approximately 40 kDa in size with a single C-type lectin-like domain at the COOH terminus, closest in homology to DC-SIGNR, DC-SIGN, and CD23. LSECtin mRNA was only expressed in liver and lymph node among 15 human tissues tested, intriguingly neither expressed on hematopoietic cell lines nor on monocyte-derived dendritic cells (DCs). Moreover, LSECtin is expressed predominantly by sinusoidal endothelial cells of human liver and lymph node and co-expressed with DC-SIGNR. LSECtin binds to mannose, GlcNAc, and fucose in a Ca(2+)-dependent manner but not to galactose. Our results indicate that LSECtin is a novel member of a family of proteins comprising CD23, DC-SIGN, and DC-SIGNR and might function in vivo as a lectin receptor.     

氨基酸营养当量和整齐性指数

化学法以蛋白质的氨基酸组成评价蛋白质营养价值。在分析化学法的一般思想和方法的基础上,本文引进氨基酸营养当量和营养当量数的概念,并提出一个称为“整齐性指数”的新化学指数。使化学评价蛋白质营养价值的方法理论化,并使化学指数在反映蛋白质营养价值上更加精确可靠;本文同时还揭示了化学法中常用的化学分指标能较理想反映蛋白质营养价值的内在原因,通过实例分析,本文还证实了蛋白质的氨基酸组成对蛋白质的消化率存在影响的作用。     

~(125)Ⅰ标记单抗LC-I与肺腺癌细胞体内外结合特性的研究

本文用~(125)Ⅰ标记LC-1进行了一些体内外实验。实验结果表明:LC-1单抗的结合常数为4.8×10~8M~(-1),LC-1针对的SPC-A_1细胞表面抗原的位点数为7.2×10~4/细胞;LC-1与LAC-122两单抗针对的抗原决定簇没有交叉;用蛋白酶和过碘酸钠处理SPC-A_1细胞,前者对LC-1的结合抑制39%,后者抑制66%;LC- 1不但有较强的体外结合靶细胞的能力,从LC-1在荷瘤裸鼠中的组织器官分布来看,LC-1与肿瘤有较高的体内亲和性,并且是特异性的结合。     

Guiding Neuronal Cell Migrations

Neuronal migration is, along with axon guidance, one of the fundamental mechanisms underlying the wiring of the brain. As other organs, the nervous system has acquired the ability to grow both in size and complexity by using migration as a strategy to position cell types from different origins into specific coordinates, allowing for the generation of brain circuitries. Guidance of migrating neurons shares many features with axon guidance, from the use of substrates to the specific cues regulating chemotaxis. There are, however, important differences in the cell biology of these two processes. The most evident case is nucleokinesis, which is an essential component of migration that needs to be integrated within the guidance of the cell. Perhaps more surprisingly, the cellular mechanisms underlying the response of the leading process of migrating cells to guidance cues might be different to those involved in growth cone steering, at least for some neuronal populations.The migration of newly born neurons is a precisely regulated process that is critical for the development of brain architecture. Neurons arise from the proliferative epithelium that covers the ventricular space throughout the neural tube, an area named the ventricular zone (VZ). From there, newly born neurons adopt two main strategies to disperse throughout the central nervous system (CNS), designated as radial and tangential migration (Hatten 1999; Marín and Rubenstein 2003). During radial migration, neurons follow a trajectory that is perpendicular to the ventricular surface, moving alongside radial glial fibers expanding the thickness of the neural tube. In contrast, tangentially migrating neurons move in trajectories that are parallel to the ventricular surface and orthogonal to the radial glia palisade (Fig. 1). Besides their relative orientation, some of the basic mechanisms underlying the movement of cells using each of these two modes of migration are also different. For example, radially migrating neurons often use radial glial fibers as substrate, whereas tangentially migrating neurons do not seem to require their support to migrate. Even so, neurons may alternate from radial to tangential movement and vice versa during the course of their migration. This suggests that both types of migrations share common principles, in particular those directly related to the cell biology of movement (Marín et al. 2006).Open in a separate windowFigure 1.Representative migrations in the developing CNS. Multiple migrations coexist during embryonic development at different areas of the central nervous system. This schema summarizes some of these migrations during the second week of the embryonic period in the mouse. Neurons use tangential and radial migration to reach their final destination; both strategies are used by the same neurons at different stages of development (i.e., cortical interneurons in the forebrain and precerebellar neurons in the hindbrain). (IML) intermediolateral region of the spinal cord; (IO) inferior olive nucleus; (LGE) lateral ganglionic eminence; (LRN) lateral reticular nucleus; (MGE) medial ganglionic eminence; (NCx) neocortex; (OB) olfactory bulb.One of the structures that better illustrates how both types of migrations are integrated during brain development is the cerebral cortex, and so we will primarily refer to studies performed on cortical neurons for this review. The adult cerebral cortex contains two main classes of neurons: glutamatergic cortical projection neurons (also known as pyramidal cells) and GABAergic interneurons. Pyramidal cells are generated in the ventricular zone (VZ) of the embryonic pallium—the roof of the telencephalon—and reach their final position by radial migration (Rakic 2007). In contrast, cortical interneurons are born in the subpallium—the base of telencephalon—and reach the cerebral cortex through a long tangential migration (Corbin et al. 2001; Marín and Rubenstein 2001).The earliest cortical neurons form a transient structure known as the preplate, around embryonic day 10 (E10) of gestation age in the mouse. This primordial layer consists of Cajal-Retzius cells and the first cohort of pyramidal neurons, which will eventually populate the subplate. Cajal-Retzius cells, which play important roles during neuronal migration, arise from discrete pallial sources and colonize the entire surface of the cortex through tangential migration (Bielle et al. 2005; Takiguchi-Hayashi et al. 2004; Yoshida et al. 2006). The next cohort of pyramidal cells forms the cortical plate (CP) by intercalating in the preplate and splitting this primitive structure in a superficial layer, the marginal zone (MZ or layer I), and a deep layer, the subplate. The development of the neocortex progresses with new waves of neurons that occupy progressively more superficial positions within the CP (Gupta et al. 2002; Marín and Rubenstein 2003). Birth dating studies have shown that layers II–VI of the cerebral cortex are generated in an “inside-out” sequence. Neurons generated earlier reside in deeper layers, whereas later-born neurons migrate past existing layers to form superficial layers (Angevine and Sidman 1961; Rakic 1974). In parallel to this process, GABAergic interneurons migrate to the cortex, where they disperse tangentially via highly stereotyped routes in the MZ, SP, and lower intermediate zone/subventricular zone (IZ/SVZ) (Lavdas et al. 1999). Interneurons then switch from tangential to radial migration to adopt their final laminar position in the cerebral cortex (Ang et al. 2003; Polleux et al. 2002; Tanaka et al. 2003).