Structural insights into the evolutionary paths of oxylipin biosynthetic enzymes

The oxylipin pathway generates not only prostaglandin-like jasmonates but also green leaf volatiles (GLVs), which confer characteristic aromas to fruits and vegetables. Although allene oxide synthase (AOS) and hydroperoxide lyase are atypical cytochrome P450 family members involved in the synthesis of jasmonates and GLVs, respectively, it is unknown how these enzymes rearrange their hydroperoxide substrates into different products. Here we present the crystal structures of Arabidopsis thaliana AOS, free and in complex with substrate or intermediate analogues. The structures reveal an unusual active site poised to control the reactivity of an epoxyallylic radical and its cation by means of interactions with an aromatic pi-system. Replacing the amino acid involved in these steps by a non-polar residue markedly reduces AOS activity and, unexpectedly, is both necessary and sufficient for converting AOS into a GLV biosynthetic enzyme. Furthermore, by combining our structural data with bioinformatic and biochemical analyses, we have discovered previously unknown hydroperoxide lyase in plant growth-promoting rhizobacteria, AOS in coral, and epoxyalcohol synthase in amphioxus. These results indicate that oxylipin biosynthetic genes were present in the last common ancestor of plants and animals, but were subsequently lost in all metazoan lineages except Placozoa, Cnidaria and Cephalochordata.     

Rapid change in drift of the Australian plate records collision with Ontong Java plateau

The subduction of oceanic plateaux, which contain extraordinarily thick basaltic crust and are the marine counterparts of continental flood-basalt provinces, is an important factor in many current models of plate motion and provides a potential mechanism for triggering plate reorganization. To evaluate such models, it is essential to decipher the history of the collision between the largest and thickest of the world's oceanic plateaux, the Ontong Java plateau, and the Australian plate, but this has been hindered by poor constraints for the arrival of the plateau at the Melanesian trench. Here we present (40)Ar-(39)Ar geochronological data on hotspot volcanoes in eastern Australian that reveal a strong link between collision of the Greenland-sized Ontong Java plateau with the Melanesian arc and motion of the Australian plate. The new ages define a short-lived period of reduced northward plate motion between 26 and 23 Myr ago, coincident with an eastward offset in the contemporaneous tracks of seamount chains in the Tasman Sea east of Australia. These features record a brief westward deflection of the Australian plate as the plateau entered and choked the Melanesian trench 26 Myr ago. From 23 Myr ago, Australia returned to a rapid northerly trajectory at roughly the same time that southwest-directed subduction began along the Trobriand trough. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks on the Pacific plate, including the archetypal Hawaiian chain, and thus provide strong evidence that immense oceanic plateaux, like the Ontong Java, can contribute to initiating rapid change in plate boundaries and motions on a global scale.     

Towards a proteome-scale map of the human protein-protein interaction network

Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.     

Stargazin modulates AMPA receptor gating and trafficking by distinct domains

AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors mediate fast excitatory synaptic transmission in the brain. These ion channels rapidly deactivate and desensitize, which determine the time course of synaptic transmission. Here, we find that the AMPA receptor interacting protein, stargazin, not only mediates AMPA receptor trafficking but also shapes synaptic responses by slowing channel deactivation and desensitization. The cytoplasmic tail of stargazin determines receptor trafficking, whereas the ectodomain controls channel properties. Stargazin alters AMPA receptor kinetics by increasing the rate of channel opening. Disrupting the interaction of stargazin ectodomain with hippocampal AMPA receptors alters the amplitude and shape of synaptic responses, establishing a crucial function for stargazin in controlling the efficacy of synaptic transmission in the brain.     

轧钢机轧辊直径的优化设计

利用非线性规划的方法,提出了轧钢机轧辊直径的设计计算的新方法。对轧钢机电子计算机辅助设计,提供了基本结构参数的模型及回归公式。     

国际拖曳水池会议水翼—头体组合空泡初生试验研究

为了研究各种因素,如水的空气含量、流速、表面粗糙以及气核对各种空泡初生的影响,在上海交通大学空泡水筒进行了国际拖曳水池会议推荐的水翼—头体组合体的试验。本文提供了试验程序和试验结果,并与其他单位的同样试验作了比较。试验结果表明各种空泡初生都受上述因素的影响,而且影响程度随空泡类型而不同。与其他单位试验结果比较,发观相互间都存在很大差异。这些差异,除了由于试验设备不同外,可能是由于对各种空泡初生缺乏统一的定义,试验技术和程序的不同等而引起的。根据十六届国际拖曳水池会议空泡委员会的要求,部分试验结果己提交该委员会并在十六届国际拖曳水池会议录空泡委员会的报告中引用。     

东北鼢鼠染色体组型和G带带型分析

通过对6只东北鼢鼠（其中3只为雄性,3只为雌性）的100个骨髓细胞的核型研究,确定东北鼢鼠的二倍体染色体数目为2n＝62。从G—带显示结果看,东北鼢鼠各染色体均有其特有带型。