Structural basis of membrane bending by the N-BAR protein endophilin

Functioning as key players in cellular regulation of membrane curvature, BAR domain proteins bend bilayers and recruit interaction partners through poorly understood mechanisms. Using electron cryomicroscopy, we present reconstructions of full-length endophilin and its N-terminal N-BAR domain in their membrane-bound state. Endophilin lattices expose large areas of membrane surface and are held together by promiscuous interactions between endophilin's amphipathic N-terminal helices. Coarse-grained molecular dynamics simulations reveal that endophilin lattices are highly dynamic and that the?N-terminal helices are required for formation of a stable and regular scaffold. Furthermore, endophilin accommodates different curvatures through?a quantized addition or removal of endophilin dimers, which in some cases causes dimerization of endophilin's SH3 domains, suggesting that the spatial presentation of SH3 domains, rather than affinity, governs the recruitment of downstream interaction partners.     

PAC对谷子花后土壤氮素供应和叶片抗氧化特性的影响

全基施肥方式会造成作物全生育期内营养供应失衡, 导致生育后期缺氮早衰。为探究聚天门冬氨酸和壳聚糖复配剂(PAC)保障谷子(Setaria italica)花后氮素供应和调控叶片抗氧化特性的机制, 建立全基施肥背景下东北春谷防衰增产的生产技术, 于2020-2021年在中国农业科学院作物科学研究所公主岭试验站开展大田试验, 以谷子品种张杂谷13号和华优谷9号为材料, 设置常规氮素(CN)和PAC配合氮素(PN) 6个氮素水平(0、75、112.5、150、225和337.5 kg·hm^-2)播种前进行全基施肥处理。结果表明, 与常规氮肥处理相比, 相同施氮量下, PAC处理后, 两品种谷子花期和灌浆中期0-20 cm和20-40 cm土层土壤硝态氮和铵态氮含量升高, 花后叶面积显著增大, 叶面积降幅减小; 花后0-40天旗叶超氧化物歧化酶、过氧化物酶及过氧化氢酶活性升高, 丙二醛含量降低。因此, PAC有效保障了谷子生育中、后期土壤氮素的供应, 提高了叶片抗氧化能力, 延缓了叶片衰老进程, 进而提高产量。2020年和2021年Z13的增产幅度分别为11.24%-21.55%和8.65%- 14.22%, H9的增产幅度分别为5.53%-15.75%和10.43%-16.17%。上述调控效应在低氮和中氮水平(75、112.5和150 kg·hm^-2)下更为显著。综上, PAC配合氮肥全基施可作为一项防衰增产的栽培技术应用于我国东北春谷区。     

森林公园在我国自然保护区系统中的地位

本文针对我国森林公园建设发展迅速的现状,阐述了“森林公园”的自然保护性质和作用,提出“国家自然保护区系统”的概念,将森林公园与自然保护区、风景名胜区三个体系同视为“国家自然保护区系统”中的三个组成部分,并阐述了这三个体系各自的特点、地位及其相互关系。同时,还提出进一步加强森林公园管理的建议。     

云南石林碳酸盐岩表面气生蓝藻(蓝细菌)研究

云南石林的黑石头及其颜色会随着天气的变化而变化的自然景观,是由于其碳酸盐岩表面长满黑色气生蓝藻（蓝细菌）之故。经鉴定,气生蓝藻共４目,１１科,３１届,１８８种。种类十分丰富。其优势种主要为寄生微囊藻、红色星球藻、伯氏伪枝藻和皮壳伪枝藻等;寄生微囊藻和红色星球藻呈面状分布,相对均衡,伯氏伪枝藻和皮壳伪枝藻呈点状分布,相对集中。这些气生蓝藻的胶被色泽鲜艳,宽厚而坚硬,是适宜高山岩石表面生活的典型进化特征。在野外肉限观察时,气生蓝藻还表现出不同形态的微群落;发现气生蓝藻能溶解石灰石,形成钻孔,加速岩石的溶蚀与风化。这些现象表明,气生蓝藻与云南石林岩石表面的微形态及整个石林景观的形成都有着十分密切的关系。     

自然保护区生态安全设计的方法研究

由于生态破坏和自然栖息地的丧失,造成野生动植物种群的破碎化．自然保护区已成为孤立的生境岛屿,目前以单个、孤立保护区为主的生物多样性保护模式是远远不够的,应在广泛的时空尺度上保护生态过程和生物多样性各组成成份,建立一个整体的保护网络．根据国内外生物多样性保护的要求和发展趋势,提出了自然保护区生态安全设计的概念,它是综合考虑了生态、社会、经济的一种协调设计战略,首先从区域层次研究保护区网络的优化设计;其次,在网络的每个节点(保护区),研究保护区的面积、形状和内部功能分区;最后,研究网络与节点的连接(廊道)．自然保护区网络设计应维持生态系统的地域完整性和生态过程完整性,采用迭代法、整数规划方法和地理途径方法,为一个或多个保护目标勾画出多种保护规划蓝图。     

Synthesis of Biomimetic Superhydrophobic Surface through Electrochemical Deposition on Porous Alumina

The superhydrophobicity of plant leaves is a benefit of the hierarchical structures of their surfaces. These structures have been imitated in the creation of synthetic surfaces. In this paper, a novel process for fabrication of biomimetic hierarchical structures by electrochemical deposition of a metal on porous alumina is described. An aluminum specimen was anodically oxidized to obtain a porous alumina template, which was used as an electrode to fabricate a surface with micro structures through electrochemical deposition of a metal such as nickel and copper after the enlargement of pores. Astonishingly, a hierarchical structure with nanometer pillars and micrometer clusters was synthesized in the pores of the template. The nanometer pillars were determined by the nanometer pores. The formation of micrometer clusters was related to the thin walls of the pores and the crystallization of the metal on a flat surface. From the as-prepared biomimetic surfaces, lotus-leaf-like superhydrophobic surfaces with nickel and copper deposition were achieved.     

荧光标记噬菌体快速检测K1荚膜大肠杆菌方法的建立及应用

【背景】大肠杆菌(Escherichia coli,E.coli)是引发新生儿脑膜炎和禽类脑膜炎最常见的革兰氏阴性菌,其中含K1荚膜大肠杆菌是重要的病原菌。目前,K1荚膜大肠杆菌的检测方法存在一些弊端。【目的】利用PNJ1809-36噬菌体的宿主特异性建立快速检测K1荚膜大肠杆菌的方法。【方法】用荧光染料SYBR Gold标记PNJ1809-36噬菌体,侵染33株受试菌,在荧光显微镜下观察,测定该方法的特异性;倍比稀释宿主菌DE058,用荧光标记噬菌体侵染,测定该方法的灵敏度;用荧光标记噬菌体检测8份模拟粪样,测定该方法的临床应用效果;测定4℃避光保存4个月的荧光标记噬菌体的效价和检测效果。【结果】33株受试菌中的9株K1荚膜大肠杆菌有8株可见环状荧光,1株未能检出;20株非K1荚膜大肠杆菌以及4株非大肠杆菌属细菌均不能观察到荧光,检测灵敏度达100CFU/mL。8份模拟粪样的检测结果显示,3份含有K1荚膜大肠杆菌的粪样均可见环状荧光,5份不含K1荚膜大肠杆菌的粪样均无荧光。荧光标记噬菌体4℃避光保存4个月后效价无明显下降,检测效果无明显变化,表明该荧光标记噬菌体在4℃避光条件下较稳定。【结论】用荧光标记的PNJ1809-36噬菌体能够在15min内特异、快速、直观地检测K1荚膜大肠杆菌。     

Mechanism of membrane curvature sensing by amphipathic helix containing proteins

There are several examples of membrane-associated protein domains that target curved membranes. This behavior is believed to have functional significance in a number of essential pathways, such as clathrin-mediated endocytosis, which involve dramatic membrane remodeling and require the recruitment of various cofactors at different stages of the process. This work is motivated in part by recent experiments that demonstrated that the amphipathic N-terminal helix of endophilin (H0) targets curved membranes by binding to hydrophobic lipid bilayer packing defects which increase in number with increasing membrane curvature. Here we use state-of-the-art atomistic simulation to explore the packing defect structure of curved membranes, and the effect of this structure on the folding of H0. We find that not only are packing defects increased in number with increasing membrane curvature, but also that their size distribution depends nontrivially on the curvature, falling off exponentially with a decay constant that depends on the curvature, and crucially that even on highly curved membranes defects large enough to accommodate the hydrophobic face of H0 are never observed. We furthermore find that a percolation model for the defects explains the defect size distribution, which implies that larger defects are formed by coalescence of noninteracting smaller defects. We also use the recently developed metadynamics algorithm to study in detail the effect of such defects on H0 folding. It is found that the comparatively larger defects found on a convex membrane promote H0 folding by several kcal/mol, while the smaller defects found on flat and concave membrane surfaces inhibit folding by kinetically trapping the peptide. Together, these observations suggest H0 folding is a cooperative process in which the folding peptide changes the defect structure relative to an unperturbed membrane.