Structural evidence for common ancestry of the nuclear pore complex and vesicle coats

Nuclear pore complexes (NPCs) facilitate nucleocytoplasmic transport. These massive assemblies comprise an eightfold symmetric scaffold of architectural proteins and central-channel phenylalanine-glycine-repeat proteins forming the transport barrier. We determined the nucleoporin 85 (Nup85)*Seh1 structure, a module in the heptameric Nup84 complex, at 3.5 angstroms resolution. Structural, biochemical, and genetic analyses position the Nup84 complex in two peripheral NPC rings. We establish a conserved tripartite element, the ancestral coatomer element ACE1, that reoccurs in several nucleoporins and vesicle coat proteins, providing structural evidence of coevolution from a common ancestor. We identified interactions that define the organization of the Nup84 complex on the basis of comparison with vesicle coats and confirmed the sites by mutagenesis. We propose that the NPC scaffold, like vesicle coats, is composed of polygons with vertices and edges forming a membrane-proximal lattice that provides docking sites for additional nucleoporins.     

Three-dimensional structure at 0.86 A of the uncomplexed form of the transmembrane ion channel peptide gramicidin A

The crystal structure of the uncomplexed orthorhombic form of gramicidin A has been determined at 120 K and at 0.86 angstrom resolution. The pentadecapeptide crystallizes as a left-handed antiparallel double-stranded helical dimer with 5.6 amino acid residues per turn. The helix has an overall length of 31 angstroms and an average inner channel diameter of 4.80 angstroms. The channel of this crystalline form is void of ions or solvent molecules. The channel diameter varies from a minimum of 3.85 angstroms to a maximum of 5.47 angstroms and contains three pockets where the cross-channel contacts are 5.25 angstroms or greater. The range of variation seen for the phi and psi torsion angles of the backbone of the helix suggests that these potential ion binding sites can be induced to travel the length of the channel in a peristaltic manner by cooperatively varying these angles. The indole rings of the eight tryptophan residues of the dimer are overlapped in three separate regions on the outer surface of the helix when viewed down the barrel of the channel. This arrangement would permit long-chained lipid molecules to nest parallel to the outer channel surface between these protruding tryptophan regions and act like molecular splines to constrain helical twist deformations of the channel.     

Nanomechanical basis of selective gating by the nuclear pore complex

The nuclear pore complex regulates cargo transport between the cytoplasm and the nucleus. We set out to correlate the governing biochemical interactions to the nanoscopic responses of the phenylalanineglycine (FG)-rich nucleoporin domains, which are involved in attenuating or promoting cargo translocation. We found that binding interactions with the transport receptor karyopherin-beta1 caused the FG domains of the human nucleoporin Nup153 to collapse into compact molecular conformations. This effect was reversed by the action of Ran guanosine triphosphate, which returned the FG domains into a polymer brush-like, entropic barrier conformation. Similar effects were observed in Xenopus oocyte nuclei in situ. Thus, the reversible collapse of the FG domains may play an important role in regulating nucleocytoplasmic transport.     

RanGTPase激活蛋白RanGAP1的研究现状

RanGTPase的活性蛋白RanGAP1位于细胞质中,是RanGTP/GDP循环的一个关键调节器,对细胞的核质运输和有丝分裂都有重要作用。RanGAP1是第一个为人们所证实的可被SUMO-1的蛋白质,SUMO化的RanGAP1位于核孔,与核孔蛋白RanBP2/Nup358及其相关因子相结合,对细胞周期起到调控作用。     

低压湿式储气罐柔索导向系统的初步研究

介绍了一种新的湿式储气罐柔索导向系统，该系统主要由按一定方式布置的滑轮组组成布，分析了这种导向系统的主要特点，它能有效地防止钟罩倾覆，与外导架直升式导向系统等相比，可在不降低抗倾覆性能的情况下显著降低导向系统的成本，探讨了该系统在工程应用中的一些问题，重点讨论了滑轮组的两种布置方案，并以１０００ｍ＾３容积储气罐为例，分析钢绳的拉力和所需的直径。指出了该导向系统在建造成本方面的优越性。     

Midbody targeting of the ESCRT machinery by a noncanonical coiled coil in CEP55

The ESCRT (endosomal sorting complex required for transport) machinery is required for the scission of membrane necks in processes including the budding of HIV-1 and cytokinesis. An essential step in cytokinesis is recruitment of the ESCRT-I complex and the ESCRT-associated protein ALIX to the midbody (the structure that tethers two daughter cells) by the protein CEP55. Biochemical experiments show that peptides from ALIX and the ESCRT-I subunit TSG101 compete for binding to the ESCRT and ALIX-binding region (EABR) of CEP55. We solved the crystal structure of EABR bound to an ALIX peptide at a resolution of 2.0 angstroms. The structure shows that EABR forms an aberrant dimeric parallel coiled coil. Bulky and charged residues at the interface of the two central heptad repeats create asymmetry and a single binding site for an ALIX or TSG101 peptide. Both ALIX and ESCRT-I are required for cytokinesis, which suggests that multiple CEP55 dimers are required for function.     

渔用麻醉剂在鱼类麻醉保活运输中应用的研究进展

为了满足广大消费者可以品尝到各地鲜活鱼类的需求,鱼的保活运输显得尤为重要,为了降低运输损伤、提高运输存活率,麻醉保活运输起到了重要作用。文章综述了4种常见渔用麻醉剂在鱼类麻醉保活运输中的应用,讨论影响麻醉保活运输存活率效果的主要因素、麻醉剂对鱼体生理生化的影响以及麻醉剂残留的检测技术,并概括了现阶段麻醉保活运输中存在的主要问题和发展前景。目前,针对渔用麻醉剂的研究主要集中在对不同水产品的麻醉效果以及对鱼体生理生化的影响,针对鱼肉风味影响方面的研究少。新型渔用麻醉剂和针对麻醉残留的快速检测技术将会是未来研究的重点。     

Functional targeting of DNA damage to a nuclear pore-associated SUMO-dependent ubiquitin ligase

Recent findings suggest important roles for nuclear organization in gene expression. In contrast, little is known about how nuclear organization contributes to genome stability. Epistasis analysis (E-MAP) using DNA repair factors in yeast indicated a functional relationship between a nuclear pore subcomplex and Slx5/Slx8, a small ubiquitin-like modifier (SUMO)-dependent ubiquitin ligase, which we show physically interact. Real-time imaging and chromatin immunoprecipitation confirmed stable recruitment of damaged DNA to nuclear pores. Relocation required the Nup84 complex and Mec1/Tel1 kinases. Spontaneous gene conversion can be enhanced in a Slx8- and Nup84-dependent manner by tethering donor sites at the nuclear periphery. This suggests that strand breaks are shunted to nuclear pores for a repair pathway controlled by a conserved SUMO-dependent E3 ligase.     

1961—2018年左权县日照时数变化特征分析

利用1961—2018年左权县逐月日照时数资料,运用线性趋势分析、相关系数分析、5年滑动平均、Mann-Kendall非参数检验和滑动t检验等方法,分析了近58年来左权县日照时数年、季节及月变化特征。结果表明,左权县年日照时数呈显著下降趋势,气候倾向率为-30.78 h/10 a;四季日照时数变化中,春季呈上升趋势,夏、秋、冬季呈下降趋势,其中夏、冬两季对年日照时数减少的贡献最大;除3月、4月外,其余各月日照时数均呈下降趋势,尤以1月、6月、12月下降趋势最为显著;年日照时数在1992年发生了减少突变。     

Residue-specific vibrational echoes yield 3D structures of a transmembrane helix dimer

Two-dimensional (2D) vibrational echo spectroscopy has previously been applied to structural determination of small peptides. Here we extend the technique to a more complex, biologically important system: the homodimeric transmembrane dimer from the α chain of the integrin α(IIb)β(3). We prepared micelle suspensions of the pair of 30-residue chains that span the membrane in the native structure, with varying levels of heavy ((13)C=(18)O) isotopes substituted in the backbone of the central 10th through 20th positions. The constraints derived from vibrational coupling of the precisely spaced heavy residues led to determination of an optimized structure from a range of model candidates: Glycine residues at the 12th, 15th, and 16th positions form a tertiary contact in parallel right-handed helix dimers with crossing angles of -58° ± 9° and interhelical distances of 7.7 ± 0.5 angstroms. The frequency correlation established the dynamical model used in the analysis, and it indicated the absence of mobile water associated with labeled residues. Delocalization of vibrational excitations between the helices was also quantitatively established.     

Voltage sensor of Kv1.2: structural basis of electromechanical coupling

Voltage-dependent ion channels contain voltage sensors that allow them to switch between nonconductive and conductive states over the narrow range of a few hundredths of a volt. We investigated the mechanism by which these channels sense cell membrane voltage by determining the x-ray crystal structure of a mammalian Shaker family potassium ion (K+) channel. The voltage-dependent K+ channel Kv1.2 grew three-dimensional crystals, with an internal arrangement that left the voltage sensors in an apparently native conformation, allowing us to reach three important conclusions. First, the voltage sensors are essentially independent domains inside the membrane. Second, they perform mechanical work on the pore through the S4-S5 linker helices, which are positioned to constrict or dilate the S6 inner helices of the pore. Third, in the open conformation, two of the four conserved Arg residues on S4 are on a lipid-facing surface and two are buried in the voltage sensor. The structure offers a simple picture of how membrane voltage influences the open probability of the channel.     

食用菌菌渣对黄褐土团聚体组成的影响

为探明不同碳氮比的食用菌菌渣对黄褐土团聚体组成和性状的影响,采用室内恒温培养试验分析了添加灰树花菌渣和双孢菇菌渣前后黄褐土水稳性团聚体的组成变化及性状指标之间的相关性。结果表明：添加菌渣主要增加了1～5 mm的水稳性团聚体百分含量,培养后1～5 mm团聚体百分含量在≥0.25 mm团聚体百分含量中占比增加了35.74%～52.88%;两种菌渣均能显著增大土壤团聚体的平均重量直径和几何均重直径,培养期内,灰树花菌渣15%和30%添加量处理的团聚体平均重量直径和几何均重直径始终显著大于1%和5%的处理,双孢菇菌渣培养30 d和60 d的处理中,团聚体性状指标随添加量变化规律不明显,培养90 d后,添加15%和30%的处理团聚体平均重量直径和几何均重直径显著高于低添加量处理;灰树花菌渣处理的团聚体性状各项指标与3～5 mm的大团聚体含量显著相关,双孢菇菌渣处理的团聚体性状指标与2～3、3～5 mm的较大团聚体和0.25～0.5、0.5～1 mm的较小团聚体含量都显著相关。研究表明,食用菌菌渣培育黄褐土能够改善土壤团聚体状态,菌渣的碳氮比是影响改善效果的重要因素,过高的碳氮比仅对大团聚体的形成...     

阿城地区大豆田除草剂残留空间分布研究

采用超高效液相色谱串联质谱法测定黑龙江省阿城地区典型耕地的大豆田中0~45 cm 不同土层豆乙合剂（乙草胺、氯嘧磺隆）中两种除草剂的残留量,研究其空间分布特征。样品经 乙腈提取,QUECHERS 法净化,测得三种除草剂的空间残留量,结果表明:（1）在各采集点土壤 中两种除草剂都有残留,乙草胺残留范围为9.16 ~ 96.26 ng/mL;氯嘧磺隆为2021.67 ~ 465287 ng/mL。并且,氯嘧磺隆的残留量明显大于乙草胺的残留量。（2）从检出的两种除草剂残留量的 垂直空间分布可知,乙草胺和氯嘧磺隆在土层中残留量的空间分布总体均呈先上升后下降的趋 势。     

三七种子的物理机械特性试验

测定了不同含水率的三七种子的三轴尺寸、密度、内摩擦角、休止角以及与不同材料间的静、动滑动摩擦角和漂浮速度。结果表明:三七种子长、宽、高范围分别为5.2~7.2 mm、4.8~6.8 mm和4.0~6.0 mm;平均直径为5.62 mm,球度为90.86%,近似球体;三七种子的密度随含水率的下降逐渐减小,且与含水率呈线性相关;种子内摩擦角、休止角、滑动摩擦角皆随含水率下降呈先减小,再增大,后减小的趋势;种子平均漂浮速度为5.77~8.96m/s,平均漂浮速度与种子含水率呈正相关。     

崇明瀛东村中心河污染特征

采用常规测试方法对村镇级河道——崇明瀛东村中心河的污染现状、影响因子进行了研究,并对其限制营养元素进行了分析。结果表明,瀛东村中心河水体处于富营养状态,磷为限制性营养元素,受人为干扰强烈,居民区和汇水区营养元素含量偏高;水体环境较适于藻类生长,具有藻类暴发的潜在威胁。     

Quisqualate activates a rapidly inactivating high conductance ionic channel in hippocampal neurons

Glutamate activates a number of different receptor-channel complexes, each of which may contribute to generation of excitatory postsynaptic potentials in the mammalian central nervous system. The rapid application of the selective glutamate agonist, quisqualate, activates a large rapidly inactivating current (3 to 8 milliseconds), which is mediated by a neuronal ionic channel with high unitary conductance (35 picosiemens). The current through this channel shows pharmacologic characteristics similar to those observed for the fast excitatory postsynaptic current (EPSC); it reverses near 0 millivolts and shows no significant voltage dependence. The amplitude of the current through this channel is many times larger than that through the other non-NMDA (N-methyl-D-aspartate) channels. These results suggest that this high-conductance quisqualate-activated channel may mediate the fast EPSC in the mammalian central nervous system.     

Structure of a site-2 protease family intramembrane metalloprotease

Regulated intramembrane proteolysis by members of the site-2 protease (S2P) family is an important signaling mechanism conserved from bacteria to humans. Here we report the crystal structure of the transmembrane core domain of an S2P metalloprotease from Methanocaldococcus jannaschii. The protease consists of six transmembrane segments, with the catalytic zinc atom coordinated by two histidine residues and one aspartate residue approximately 14 angstroms into the lipid membrane surface. The protease exhibits two distinct conformations in the crystals. In the closed conformation, the active site is surrounded by transmembrane helices and is impermeable to substrate peptide; water molecules gain access to zinc through a polar, central channel that opens to the cytosolic side. In the open conformation, transmembrane helices alpha1 and alpha6 separate from each other by 10 to 12 angstroms, exposing the active site to substrate entry. The structure reveals how zinc embedded in an integral membrane protein can catalyze peptide cleavage.     

拟南芥核膜孔蛋白Nup160基因的突变体表型分析

植物开花受环境条件的影响,其分子调控机制在转录、翻译和表观遗传等层次已有较广泛而深入的研究;核膜孔复合物是真核细胞中细胞质与细胞核之间物质交换的重要通道。筛选到拟南芥核膜孔蛋白Nup（Nucleoporin） 160基因的3个突变体nup160-1/-2/-3,均表现出发育的多种表型,最显著的表型为早花,而且是不依赖于环境条件（光周期和温度）的早花。但是,突变体在长日下的开花时间依然早于短日条件下的开花时间,暗示突变体仍然对光周期有反应。结果表明,在拟南芥中Nup160作为一个植物开花的负调控因子,主要在温敏途径和光周期途径中参与拟南芥开花时间的调节。     

The Tunguska Explosion of 1908: Discovery of Meteoritic Debris near the Explosion Site and at the South Pole

Submillimeter-sized metallic spheres extracted from soil in the Tunguska region of central Siberia contain noble metals in cosmic proportions. The trace element composition and geographical distribution of these spheres suggest that they are from the 30 June 1908 Tunguska explosion and not meteoritic ablation products falling continuously on the earth. Debris from this explosion was also discovered in a South Pole ice core; this discovery indicates that the Tunguska object exploded in the atmosphere with subsequent stratospheric injection and transport of the debris. The celestial body that exploded over Tunguska weighed more than 7 million tons, was more than 0.16 kilometer in diameter, and may well have been a stony meteorite. This discovery offers a new precision time marker in polar ice strata for the year 1909. The steady-state influx of cosmic matter at the South Pole is estimated to be 1.8 x 10(-8) grams per square centimeter per year, which corresponds to a global influx of 4 x l0(5) tons per year.     

诸暨市古树资源调查研究

经全面调查,确定浙江省诸暨市有古树45 109株,隶属38科65属90种.其中树龄最大的为1 350 a,胸径最大2.95 m.提出了古树保护管理的6条建议.参3