Interaction of synthetic peptide corresponding to signal sequence of glucitol permease of Escherichia Coli and its analogue with liposomes

The N-terminal signal sequence of glucitol pcrmease of Escherichia Coli (Gut22) and its analogue (Gut22Ana) were synthesized. The analogue had a Pro residue substituting for the His at the 7th position of Gut22 and a Val residue substituting for the Glu at the 10th position. The intrinsic fluorescence emission spectra indicated that the binding of Gut22 with lipid bilayer was much stronger than that of Gut22Ana. The leakage experiments with calcein-loaded liposomes showed that Gut22 strongly perturbed lipid bilayers while Gut22Ana did not. The apparent partition constant of Gut22 for partitioning into phosphatidylserine/phosphatidylcholine bilayers was measured; the effect of membrane potential on the interaction of Gut22 with lipid bilayers was studied and the conformation changes of Gut22 and Gut22Ana upon interacting with liposomes were studied by the method of circular dichroism analysis.     

人Ⅳ型胶原的提纯及其抗血清制备

采用胃蛋白酶限制性消化,NaCl分级盐析,还原和烷基化反应,纤维素离子交换层析从人胎盘组织分离纯化Ⅳ型胶原.经SDS-PAGE电泳鉴定符合Ⅳ型胶原α肽链电泳带.用纯化的Ⅳ型胶原免疫兔制备出高效价的特异抗血清.     

Non-crystallographic symmetry of crystal of neutral phospholipase A2 from Agkistrodon halys Pallas

Agkistrodotoxin, a neutral phospholipase A₂ with high presynaptic neurotoxicity from the venom of Agkistrodon halys Pallas, has been crystallized by hanging drop vapor diffusion method. The crystal belongs to P2₁ space group with the cell dimensions a = 10.836 nm, b=8.486nm, c = 7.082nm, β=109.87$ showing C2 pseu-do-symmetry. Diffraction data to 0. 26 nm resolution have been collected on a Siemens X-200B area detector. C2 pseu-do-symmetry suggests that there exists a non-crystallographic two-fold axis parallel to crystallographic b axis. Self-rotation function calculation with different integrated radius and resolution ranges using the program POLARRFN yields four stable high peaks corresponding to three more non-crystallographic two-fold axis and one special non-crystal-lographic symmetry. The molecules in the asymmetric unit are suggested to be arranged in a manner of "dimer of dimers" by inference.     

瘤瘿螨属四新种一新亚种记述(蜱螨亚纲:瘿螨科)

本文记述的四个新种是木樨瘤瘿螨Aceria osmanthis Kuang,燕麦瘤瘿螨Aceria avenae Kuang et Zhang,江苏瘤瘿螨Aceria jiangsunensis Kuang和昆明瘤瘿螨Aceria kunmiaensis Kuang et Hong,新亚种是中华柑桔瘤瘤螨Aceria sheldoni chinensis Kuang et Hong。     

海鲍分离微生物Acinetobacter sp.酯酶基因的表达和酶学性质

【目的】克隆源于海鲍内脏中一株不动杆菌Acinetobacter sp.的酯酶基因estA,并对其进行重组表达和性质研究。【方法】利用分子生物学技术克隆出酯酶基因estA并构建pPICZα-C-estA重组表达载体,并通过电转化方法将重组质粒转入毕赤酵母X33中;通过甲醇诱导培养重组菌获得重组酯酶,并对重组酯酶进行生化表征。【结果】克隆得到的estA基因序列全长912 bp,编码304个氨基酸;重组X33发酵上清液中酯酶酶活力达到1 200 U/L,重组酯酶的分子量约为33.7 kD;酶学性质研究表明重组酯酶催化底物对硝基苯乙酸乙酯水解反应的最适pH和温度为8.0和40?C,在pH 8.0-10.0温度及小于60?C时具有较好的稳定性。【结论】成功克隆了海洋来源的不动杆菌酯酶基因并在Pichia pastoris中实现了高效表达。