双分子荧光互补技术及其在蛋白互作研究中的应用

双分子荧光互补（bimolecula fluorescence complementation,BiFC）是近年新发展起来的在活细胞中研究蛋白质互作及其定位的新技术．该技术巧妙的将荧光蛋白切成不发光的两个片段,并与目的蛋白融合表达．如果目的蛋白相互作用,连接其上的荧光互补蛋白片段将会相互靠近并恢复荧光活性,从而实现了分子与细胞事件的可视化．BiFC既可以验证蛋白之间的互作、检测其互作强弱,还可以定位互作蛋白的位点．基于双分子荧光蛋白的应用已经越来越广泛,本文对双分子荧光互补技术的原理、应用现状、特点及其面临的问题进行了概述．     

Extrafloral nectaries mediate the arboreal beetle community (Coleoptera) in a Neotropical rainforest

ABSTRACT

Nectaries are structures that secrete a sugary solution and can occur on vegetative and/or reproductive parts of plants. The significance of floral nectaries to reward vertebrate and arthropod pollinators is well supported. The role of extrafloral nectaries (EFNs) is more ambiguous, though research has been skewed to the ant-plant mutualism. Many other insects feed at EFNs, but these interactions are vastly understudied. This study addresses the hypothesis that EFNs may influence the occurrence and structure of Neotropical canopy beetle communities. Seven canopy trees (four families) exhibiting EFNs and their associated beetles were studied over a one-year period in southern Venezuela. In total, 6818 adult beetles identified to 868 species were recorded on 25 investigated canopy tree species (#47 individuals). Of the 868 beetle species, 150 species (517 individuals; 17.3% species) from 20 families were observed drinking from foliar EFNs on seven EFN-bearing tree species. Dietary dependence on EF nectar varied, with 95 beetle species utilising this nectar within a broader diet and 55 species found feeding exclusively on EFNs. This study demonstrates unequivocally that EF nectar is a frequently utilised food resource of many beetle adults and beetles have been a significantly underestimated visitor group. A more detailed study was conducted on six individual canopy trees of two species of Chrysobalanaceae, Licania hebantha Mart. ex Hook. f. and Moquilea subarachnophylla (Cuatrec.) Sothers and Prance. In total, 115 individual adults of 64 beetle species were collected on nectar secreted on newly-sprouted leaves. These beetle assemblages were dominated by species utilising EF nectar and were associated with distinct phenological phases of the host trees. Altogether, the beetle survey found support for the hypothesis that EFNs influence the occurrence and structure of beetle communities. These beetle-EFN relationships have implications for spatial arrangement, community assembly and evolution of both host plants and beetles. Like ant-EFN mutualism, EFN-bearing trees and beetles may also form mutualism. It is possible that the plants offer easier access to a nutritious resource that may deflect herbivory of vegetative parts.     

Light-harvesting complexes of vascular plants

Light-harvesting complexes (LHCs) located in the thylakoid membrane of plant chloroplasts are the collectors of solar radiation that fuel photosynthesis, and thus enable life on our planet. They consist of pigments that are non-covalently bound to light-harvesting proteins (Lhc proteins), which form a family whose members share a significant sequence identity. Due to their central role in photosynthesis, LHCs belong in several respects to the best-analysed membrane proteins. In the past decade, tremendous progress has been made in identifying new members of the Lhc family, in localising the LHCs within the photosystems, and in elucidating the structure and function of LHCs, which is summarised in this review. By contrast, gaining insight into the assembly process and the degradation of the LHCs could not keep pace. Therefore, topics for the next decade will be the elucidation of the location(s) and the operating mode of steps in the assembly and degradation process. Received 15 June 2008; received after revision 1 July 2008; accepted 10 July 2008     

Cellular uptake of amelogenin,and its localization to CD63, and Lamp1-positive vesicles

Proteins of the developing enamel matrix include amelogenin, ameloblastin and enamelin. Of these three proteins amelogenin predominates. Protein-protein interactions are likely to occur at the ameloblast Tomes’ processes between membrane-bound proteins and secreted enamel matrix proteins. Such protein-protein interactions could be associated with cell signaling or endocytosis. CD63 and Lamp1 are ubiquitously expressed, are lysosomal integral membrane proteins, and localize to the plasma membrane. CD63 and Lamp1 interact with amelogenin in vitro. In this study our objective was to study the molecular events of intercellular trafficking of an exogenous source of amelogenin, and related this movement to the spatiotemporal expression of CD63 and Lamp1 using various cell lineages. Exogenously added amelogenin moves rapidly into the cell into established Lamp1-positive vesicles that subsequently localize to the perinuclear region. These data indicate a possible mechanism by which amelogenin, or degraded amelogenin peptides, are removed from the extracellular matrix during enamel formation and maturation. Received 27 September 2006; received after revision 24 November 2006; accepted 5 December 2006     

Fast Parallel Cutoff Pair Interactions for Molecular Dynamics on Heterogeneous Systems

Heterogeneous systems with both Central Processing Units (CPUs) and Graphics Processing Units (GPUs) are frequently used to accelerate short-ranged Molecular Dynamics (MD) simulations. The most time-consuming task in short-ranged MD simulations is the computation of particle-to-particle interactions. Beyond a certain distance, these interactions decrease to zero. To minimize the operations to investigate distance, previous works have tiled interactions by employing the spatial attribute, which increases the memory access and GPU computations, hence decreasing performance. Other studies ignore the spatial attribute and construct an all-versus-all interaction matrix, which has poor scalability. This paper presents an improved algorithm. The algorithm first bins particles into voxels according to the spatial attributes, and then tiles the all-versus-all matrix into voxel-versus-voxel sub-matrixes. Only the sub-matrixes between neighboring voxels are computed on the GPU. Therefore, the algorithm reduces the distance examine operations and limits additional memory access and GPU computations. This paper also adopts a multi-level programming model to implement the algorithm on multi-nodes of Tianhe-lA. By employing (1) a patch design to exploit parallelism across the simulation domain, (2) a communication overlapping method to overlap the communications between CPUs and GPUs, and (3) a dynamic workload balancing method to adjust the workloads among compute nodes, the implementation achieves a speedup of 4.16x on one NVIDIA Tesla M2050 GPU compared to a 2.93 GHz six-core Intel Xeon X5670 CPU. In addition, it runs 2.41x faster on 256 compute nodes of Tianhe-lA (with two CPUs and one GPU inside a node) than on 256 GPU-excluded nodes.     

非共价相互作用对中心手性的影响及中心手性的定义

建立在van't Hoff碳正四面体构型学说基础上的中心手性的概念未涉及非共价相互作用对分子中心手性的影响.可以想像,当某原子连有两个相同的原子或基团(如氢原子)时,可因非共价相互作用(如分子内氢键)的存在(如只与其中的一个氢原子形成氢键)成为不等性原子或基团.考虑到非共价相互作用对分子中心手性可能产生的影响,中心手性的概念似应为:一个原子(如C,N)的四支键分别指向四面体的各顶点,并分别键连四个不等性原子或基团(包括孤电子对)时,则该原子是手性的.     

小直径血管支架的仿生构建及其种子细胞

静电纺丝仿生天然细胞外基质(ECM)结构,所制备的高度多孔、高比表面积的纳米级(50～500nm)纤维赋予了丰富的分子架构和生化信号,为种子细胞提供理想的生长微环境.不同组分、纤维尺寸及取向和种子细胞类型,可以裁剪获得不同生化和力学性能的电纺支架细胞复合物.总结了血管组织工程仿生ECM的设计与构建,并强调与支架复合的种子细胞在血管组织工程的作用.     

FVM结合PDF方法研究湍流射流火焰中的辐射换热

为了考察湍流燃烧过程中的辐射换热效应，用有限体积和概率密度函数输运方程求解相结合的方法模拟了湍流自由射流火焰中的辐射换热，并对湍流辐射交互作用进行研究．计算结果表明，辐射换热作用将使火焰的温度有所降低；湍流辐射交互作用使辐射换热有较大幅度的增强，需要在辐射换热计算中予以考虑．     

Heparan sulfate-protein interactions: therapeutic potential through structure-function insights

Heparin and the related glycosaminoglycan, heparan sulfate, bind a myriad of proteins. The structural diversity of heparin and heparan sulfates is enormous, but differences in the conformational flexibility of the monosaccharide constituents add extra complexity and may influence protein binding. Silencing genes for heparin/ heparan sulfate biosynthetic enzymes profoundly affects mammalian development. Thus, altering the structure of heparan sulfate chains can alter protein binding and embryo development. Different heparan sulfate structures are located in particular tissue sites, and these structures are recognised by different sets of proteins. Regulation of certain heparan sulfate-protein interactions by pH or cations is described. Heparin/heparan sulfate structures are viewed as potential therapeutics for a variety of diseases. An understanding at the molecular and functional levels of the specificity and affinity of heparan sulfate-protein interactions is crucial for designing heparin-inspired drugs. How the development of synthesis techniques is facilitating structure-function analyses and drug development is discussed.Received 6 July 2004; received after revision 16 September 2004; accepted 28 September 2004