花鳗鲡病原菌弗氏柠檬酸杆菌的鉴定

首次报道了从养殖花鳗鲡(Anguilla marmorata)肝脏中分离得到优势菌株AMRB6,经人工腹腔注射感染健康花鳗鲡试验,结果证实该菌有致病作用,其半数致死量LD50为3.2×107CFU/mL.结合菌体形态特征、常规生理生化鉴定和Biolog自动微生物鉴定系统鉴定,以及16S rRNA序列扩增结果,表明该菌为弗氏柠檬酸杆菌(Citrobacter freundii).30种药物药敏试验结果表明,该菌株对左氧氟沙星、诺氟沙星、庆大霉素、卡那霉素等14种药物高度敏感.     

锦鲤弗氏柠檬酸杆菌的鉴定

对从病死锦鲤（cyprinuscarpioL．）肝组织中分离的2株菌（编号：HC050630B-1,HC050630B-2）进行了形态特征、主要理化特性、对健康鲤鱼的致病作用、药物敏感性等方面的检验;同时测定了HCOS0630B-1株菌的16SrRNA基因序列,构建了系统发育树。结果表明,2株被检菌为弗氏柠檬酸杆菌（C...     

Bone recognition mechanism of porcine osteocalcin from crystal structure

Osteocalcin is the most abundant noncollagenous protein in bone, and its concentration in serum is closely linked to bone metabolism and serves as a biological marker for the clinical assessment of bone disease. Although its precise mechanism of action is unclear, osteocalcin influences bone mineralization, in part through its ability to bind with high affinity to the mineral component of bone, hydroxyapatite. In addition to binding to hydroxyapatite, osteocalcin functions in cell signalling and the recruitment of osteoclasts and osteoblasts, which have active roles in bone resorption and deposition, respectively. Here we present the X-ray crystal structure of porcine osteocalcin at 2.0 A resolution, which reveals a negatively charged protein surface that coordinates five calcium ions in a spatial orientation that is complementary to calcium ions in a hydroxyapatite crystal lattice. On the basis of our findings, we propose a model of osteocalcin binding to hydroxyapatite and draw parallels with other proteins that engage crystal lattices.     

Molecular structure of the acyl-enzyme intermediate in beta-lactam hydrolysis at 1.7 A resolution.

The X-ray crystal structure of the molecular complex of penicillin G with a deacylation-defective mutant of the RTEM-1 beta-lactamase from Escherichia coli shows how these antibiotics are recognized and destroyed. Penicillin G is covalently bound to Ser 70 0 gamma as an acyl-enzyme intermediate. The deduced catalytic mechanism uses Ser 70 0 gamma as the attacking nucleophile during acylation. Lys 73 N zeta acts as a general base in abstracting a proton from Ser 70 and transferring it to the thiazolidine ring nitrogen atom via Ser 130 0 gamma. Deacylation is accomplished by nucleophilic attack on the penicilloyl carbonyl carbon by a water molecule assisted by the general base, Glu 166.     

纳米TiO_2晶型转化机制探讨

根据统计物理学方法推导出锐钛矿型TiO_2向金红石型TiO_2转化率关系式为InX_A=-v_0texp(-2U_x/kT),其中X_A为TiO_2中锐钛矿型的含量,v_0和U_x分别锐钛矿型TiO_2原子的振动频率和势函数,t、k和T分别为煅烧时间、玻兹曼常数和煅烧温度.TiO_2为三原子分子,理论上v_0和U_x计算十分复杂,本文通过在不同温度及时间下煅烧氨水水解TiOSO_4产物的方式制备了锐钛矿型、混晶型及金红石型纳米TiO_2粉末,将XRD分析所测数据及相应温度、时间条件代入转化率关系式,拟合求得:v_0=5.3×10~(10)/s,U_x=2.71×10~(-12)J.实验所测_A-t及X_A-T曲线与计算拟合曲线吻合较好,说明用氨水水解TiOSO_4产物的方式制备的锐钛矿型纳米TiO_2向金红石型纳米TiO_2的转化为扩散型转变.     

Crystal structure of enolase indicates that enolase and pyruvate kinase evolved from a common ancestor

Enolase or 2-phospho-D-glycerate hydrolase catalyses the dehydration of 2-phosphoglycerate to phosphoenolpyruvate, which in turn is converted by pyruvate kinase to pyruvate. We describe here the crystallographic determination of the structure of yeast enolase at high resolution (2.25 A) and an analysis of the structural homology between enolase, pyruvate kinase and triose phosphate isomerase. Each of the two subunits of enolase forms two distinctive domains. The larger domain (residues 143-420) is a regular 8-fold beta/alpha-barrel, as first found in triose phosphate isomerase, and later in pyruvate kinase and 11 other functionally different enzymes. An analysis of the molecular geometries of enolase and pyruvate kinase based on the roughly 8-fold symmetry of the barrel showed a structural homology better than expected for proteins related by convergent evolution. We argue that enolase and pyruvate kinase have evolved from a common ancestral multifunctional enzyme which could process phosphoenolpyruvate in both directions along the glycolytic pathway. There is structural and sequence evidence that muconate lactonizing enzyme later evolved from enolase.     

TBC-domain GAPs for Rab GTPases accelerate GTP hydrolysis by a dual-finger mechanism

Rab GTPases regulate membrane trafficking by cycling between inactive (GDP-bound) and active (GTP-bound) conformations. The duration of the active state is limited by GTPase-activating proteins (GAPs), which accelerate the slow intrinsic rate of GTP hydrolysis. Proteins containing TBC (Tre-2, Bub2 and Cdc16) domains are broadly conserved in eukaryotic organisms and function as GAPs for Rab GTPases as well as GTPases that control cytokinesis. An exposed arginine residue is a critical determinant of GAP activity in vitro and in vivo. It has been expected that the catalytic mechanism of TBC domains would parallel that of Ras and Rho family GAPs. Here we report crystallographic, mutational and functional analyses of complexes between Rab GTPases and the TBC domain of Gyp1p. In the crystal structure of a TBC-domain-Rab-GTPase-aluminium fluoride complex, which approximates the transition-state intermediate for GTP hydrolysis, the TBC domain supplies two catalytic residues in trans, an arginine finger analogous to Ras/Rho family GAPs and a glutamine finger that substitutes for the glutamine in the DxxGQ motif of the GTPase. The glutamine from the Rab GTPase does not stabilize the transition state as expected but instead interacts with the TBC domain. Strong conservation of both catalytic fingers indicates that most TBC-domain GAPs may accelerate GTP hydrolysis by a similar dual-finger mechanism.     

结构加成水解法合成二聚环戊二烯改性不饱和聚酯

制备了相关模型化合物 ,应用化学分析、NMR分析方法进行鉴定 ,提出结构加成水解法合成二聚环戊二烯改性不饱和聚酯的反应机理 .合成反应过程中 ,二聚环戊二烯降冰片环上的9、10双键与顺丁烯二酸的羧基在H+存在下发生加成反应 ,生成顺丁烯二酸—DCPD酯 .在合成反应过程中二聚环戊二烯是端基封闭剂 ,无Diels -Alder加成反应发生     

一个层状铅膦酸盐化合物的合成及晶体结构研究

通过水热法合成了一个新化合物,Pb3(HL)2.2H2O1,(H4L=C6H11N(CH2PO3H2)2)。通过X射线单晶衍射仪测定其晶体结构。并对其进行了元素分析,红外光谱以及热重等性质测定。晶体结构研究结果表明,这个化合物属单斜晶系,空间群为C2/c,a=38.4018(8),b=7.4197(3),c=10.1180(4),β=100.610(2)°,Z=4,V=2833.63(17)3,最终偏差因子R1=0.0779,wR2=0.1452(对I>2(σI)的衍射点)和R1=0.1308,wR2=0.1752(对所有衍射点)。化合物中,铅通过桥连二膦酸配体形成一个<200>有机无机杂化层,层与层之间通过范德华力相连形成超分子结构。     

一个层状铅膦酸盐化合物的合成及晶体结构研究

通过水热法合成了一个新化合物,Pb3(HL)2·2H2O1,(H4L=C6H11N(CH2PO3H2)2).通过x射线单晶衍射仪测定其晶体结构.并对其进行了元素分析,红外光谱以及热重等性质测定.晶体结构研究结果表明,这个化合物属单斜晶系,空间群为C2/c,a=38.4018(8),b=7.4197(3),c=10.1180(4)(A),β=100.610(2)°,Z=4,V=2833.63(17)(A)3,最终偏差因子R1=0.0779,wR2=0.1452(对I＞2σ(I)的衍射点)和R1=0.1308,wR2=0.1752(对所有衍射点).化合物中,铅通过桥连二膦酸配体形成一个《200》有机无机杂化层,层与层之间通过范德华力相连形成超分子结构.     

The crystal structure of a voltage-gated sodium channel

Voltage-gated sodium (Na(V)) channels initiate electrical signalling in excitable cells and are the molecular targets for drugs and disease mutations, but the structural basis for their voltage-dependent activation, ion selectivity and drug block is unknown. Here we report the crystal structure of a voltage-gated Na(+) channel from Arcobacter butzleri (NavAb) captured in a closed-pore conformation with four activated voltage sensors at 2.7?? resolution. The arginine gating charges make multiple hydrophilic interactions within the voltage sensor, including unanticipated hydrogen bonds to the protein backbone. Comparisons to previous open-pore potassium channel structures indicate that the voltage-sensor domains and the S4-S5 linkers dilate the central pore by pivoting together around a hinge at the base of the pore module. The NavAb selectivity filter is short, ～4.6?? wide, and water filled, with four acidic side chains surrounding the narrowest part of the ion conduction pathway. This unique structure presents a high-field-strength anionic coordination site, which confers Na(+) selectivity through partial dehydration via direct interaction with glutamate side chains. Fenestrations in the sides of the pore module are unexpectedly penetrated by fatty acyl chains that extend into the central cavity, and these portals are large enough for the entry of small, hydrophobic pore-blocking drugs. This structure provides the template for understanding electrical signalling in excitable cells and the actions of drugs used for pain, epilepsy and cardiac arrhythmia at the atomic level.     

呋喃甲醛缩4-氨基安替比林Schiff碱的合成及晶体结构研究

目的 合成一种新的安替比林Schiff碱.方法 以呋喃甲醛和4-氨基安替比林为原料,通过缩合反应合成一种新的Schiff碱(C16H15N3O2,Mr = 281.31),并采用元素分析,X-射线单晶衍射法对其结构进行表征.结果 与结论该化合物属于单斜晶系P21/c点群,晶胞参数为a = 0.111 50(3)nm,b = 0.099 06(3)nm,c = 0.136 24(4)nm,β = 106.360(4)°,V = 1.443 9(7)nm3,Z = 4,Dc = 1.294 g/cm3,F(000) = 592,μ = 0.088 mm-1,R = 0.057 7以及wR = 0.121 4.标题化合物以C6=N3为中心呈E构型,C=N双键使得整个结构趋于共面,呋喃环和吡唑环所形成的二面角的平面角为6.3°.     

一个混合硫酸盐-亚硒酸盐化合物的合成和晶体结构研究

通过水热法合成了一个具有三维无机框架结构的新颖的化合物Cd4(SeO3)2(SO4)2(1).该化合物是首个第二副族的混合硫酸盐-亚硒酸盐化合物.通过X射线单晶衍射仪测定其晶体结构.晶体结构研究结果表明,这个化合物中的镉原子具有独特的三种配位模式,即,六、七和八配位构型.     

一种salen镍配合物的合成与晶体结构

合成和表征了一种新的salen镍配合物,并报道了其单晶衍射数据.化合物4:[NiC28H20Cl2N2O2]·CH2Cl2,M=631.00,单斜,P21/c,a=1.1086(2)nm,b=1.7521(4)nm,c=1.4819(3)nm,β=105.06(3)°,Z=4,V=2.779 5(10)nm3,Dc=1.508 g/cm3,R1=0.0531,R2=0.1136.     

一个混合硫酸盐-亚硒酸盐化合物的合成和晶体结构研究

通过水热法合成了一个具有三维无机框架结构的新颖的化合物Cd4(SeO3)2(SO4)2(1)。该化合物是首个第二副族的混合硫酸盐-亚硒酸盐化合物。通过X射线单晶衍射仪测定其晶体结构。晶体结构研究结果表明,这个化合物中的镉原子具有独特的三种配位模式,即,六、七和八配位构型。     

Fixation for the helical structure of a glassy cholesteric liquid crystal reflective film

The planar texture of glassy cholesteric siloxane cyclic side-chain liquid crystals was fixed by quenching initially. Then the polymer network formed by the optically active polymerizable monomers imposed additional constraints on the motion of chain seg-ments of the glassy liquid crystal and then further stabilized the molecule arrangement. A cholesteric liquid crystal film with stable optical properties was developed by this method.     

Analysis of cDNA for human erythrocyte ankyrin indicates a repeated structure with homology to tissue-differentiation and cell-cycle control proteins

Analysis of complementary DNA for human erythroid ankyrin indicates that the mature protein contains 1,880 amino acids comprising an N-terminal domain binding integral membrane proteins and tubulin, a central domain binding spectrin and vimentin, and an acidic C-terminal 'regulatory' domain containing an alternatively spliced sequence missing from ankyrin variant 2.2. The N-terminal domain is almost entirely composed of 22 tandem 33-amino-acid repeats. Similar repeats are found in yeast and invertebrate proteins involved in cell-cycle control and tissue differentiation.     

Insights into microtubule nucleation from the crystal structure of human gamma-tubulin

Microtubules are hollow polymers of alphabeta-tubulin that show GTP-dependent assembly dynamics and comprise a critical part of the eukaryotic cytoskeleton. Initiation of new microtubules in vivo requires gamma-tubulin, organized as an oligomer within the 2.2-MDa gamma-tubulin ring complex (gamma-TuRC) of higher eukaryotes. Structural insight is lacking regarding gamma-tubulin, its oligomerization and how it promotes microtubule assembly. Here we report the 2.7-A crystal structure of human gamma-tubulin bound to GTP-gammaS (a non-hydrolysable GTP analogue). We observe a 'curved' conformation for gamma-tubulin-GTPgammaS, similar to that seen for GDP-bound, unpolymerized alphabeta-tubulin. Tubulins are thought to represent a distinct class of GTP-binding proteins, and conformational switching in gamma-tubulin might differ from the nucleotide-dependent switching of signalling GTPases. A crystal packing interaction replicates the lateral contacts between alpha- and beta-tubulins in the microtubule, and this association probably forms the basis for gamma-tubulin oligomerization within the gamma-TuRC. Laterally associated gamma-tubulins in the gamma-TuRC might promote microtubule nucleation by providing a template that enhances the intrinsically weak lateral interaction between alphabeta-tubulin heterodimers. Because they are dimeric, alphabeta-tubulins cannot form microtubule-like lateral associations in the curved conformation. The lateral array of gamma-tubulins we observe in the crystal reveals a unique functional property of a monomeric tubulin.     

一种α,β不饱和羧酸亚胺酯的合成、表征与晶体结构

报道了一种烯酮亚胺反应活性中间体的重排产物——α,β不饱和羧酸亚胺酯化合物的合成,并通过核磁共振氢谱和X射线单晶衍射对其结构进行了表征.单晶X-衍射分析表明:该化合物三斜晶系,P-1空间群,晶胞参数a=7.9832(2)?,b=8.3409(2)?,c=14.5288(4)?,α=81.1650(10)°,β=74.4740(10)°,γ=63.9960(10)°,V=837.03(4)?~3.实验结果为烯酮亚胺的重排反应这一化学理论提供了有力的证据.