固相萃取/毛细管气相色谱法测定肉桂皮中六六六、滴滴涕农药残留量

研究了肉桂皮中六六六、滴滴涕农药残留量的测定方法。以丙酮-石油醚混合溶剂为提取剂,旋涡振荡提取,采用固相萃取技术对提取液净化,优化洗脱溶剂的比例和用量,用气相色谱/微电子捕获检测器(μECD)测定。在优化条件下,BHC及DDT农药在10~1 000μg/L质量浓度范围内线性关系良好,相关系数为0.995 8~0.998 1。2种农药在肉桂皮中的加标回收率为92.1%~112%,相对标准偏差(RSD)为2.8%~8.1%,方法的检出限(LODs)为5.0×10-3~2.4×10-2mg·kg-1,定量下限(LOQs)为1.3×10-2~6.0×10-2mg·kg-1。方法具有简单、灵敏、选择性高、重现性好等优点。     

井下机车的超声编码报号

本文从井下机车编码报号的实际要求出发，研制了适当的超声换能器、电子线路及单片机处理系统．     

钢窗密封胶粘剂Ⅰ号的研制

以氯丁橡胶为主原料,添加增粘树脂改性,采用沥青和混合溶剂制成钢窗密封胶粘剂Ⅰ号。此胶粘剂与同类型丹麦进口的S—90胶粘剂多数性能相当,有些性能还较优越,完全可以代替进口密封胶的使用。     

A DETERMINATION OF THE THREE-DIMENSIONAL STRUCTURE OF TRICHOSANTHIN AT LOW RESOLUTION

Trichosanthin, extracted from a Chinese herb medicine, is a plant protein having a molec-ular weight of ca. 24,000 and containing 219 amino acid residues. The crystal is mono-clinic, belonging to the space group C2, with the following cell dimensions: a=75.64A, b=75.52A, c=88.85A β= 99.51°. Each asymmetric unit contains two such protein molecules. The UO_2Ac_2 and K_2Pt(NO_2)_4 derivatives of trichosanthin have been prepared by soakingin the respective solutions of high dilution. The joint probability of isomorphous replacementand anomalous scattering has been used to calculate the native phases. In the electron densitymaps, the boundary between the two protein molecules can be recognized, leading to thefollowing approximate molecular dimensions: 45×40×35A~3. Each molecule contains fourrod-shaped segments easily known as α-helices.     

THE COURSE OF THE POLYPEPTIDE CHAIN OF TRICHOSANTHIN MOLECULE

The course of the polypeptide chain of Trichosanthin has been determined from the electron density map at 4 resolution. The structure belongs to α+β type. It contains eight α-helices (39% of total residues) and four β-sheets (32% of total residues) which are made up of thirteen β-strands. The α-helices are relatively in the centre of the molecule and surrounded by β-sheets. This is the characteristic feature of Trichosanthin structure. This kind of structural arrangement has not been reported before. The transformation matrix and translation vector, which superpose two molecules in one asymmetric unit, were obtained. The root mean square error is 1.31 for this superposition.     

天花粉蛋白分子的肽链走向

本文证明从4分辨率的电子密度图上确定了一条合理的肽走向。天花粉蛋白属于α β型结构。整个分子包含八段α-螺旋,约占残基总数37％;13条β链组成4个β折叠层,占残基总数32％。α-螺旋相对地处于分子的中心,而4个β折叠层分布在外围。这是天花粉蛋白结构的显著特点,这种结构排布方式尚未见文献报道。用坐标叠合方法获得了不对称单位内两分子叠合时的旋转矩阵和平移向量,叠合后的均方根误差是1.31。     

The Crystal and Molecular Structure of Trichosanthin at 2.6 Resolution

The crystallographic refinement of trichosanthin has been performed at 2.6 resolution. The crystal and molecular structure of trichosanthin is described in detail in this paper. On summarizing the regularity of the amino acid sequences of eight kinds of ribosome inactivating proteins and combining with the crystal and molecular structure of trichosanthin, fifteen most conservative amino acid residues are analyzed. It is found that four most conservative polar amino acid residues Gln156, Glu160, Arg163 and Glu189 gather on the molecular surface on the boundary of the large and small domains, thus forming the active center of the protein molecule.     

十二硼十二氢镍乙二胺晶体结构的研究

Ni(en)_3B_(12)H_(12)晶体属于三方晶系,空间群为R_3,晶胞参数为:a=b=12.890(2),c=23.955(20),α=B=90°,Υ=120°,Z=6。在室温下用CAD-4衍射仪收集单晶衍射强度数据(MOK_α);重原子法和差Fourier法解出全部非氢原子坐标,用加氢程序定出全部氢原子的坐标。各原子坐标及热振动参数经全矩阵最小二乘方修正,对于985个独立衍射点[I≥3σ(I)]最后偏离因子R=0.069。结构分析表明,该化合物属于离子型,Ni(en)_-~(2+)离子和B_(12)H_(12)~(-2)离子间相互以正三角双锥方式配位。Ni(en)~(2+)离子具有D_3对称性,Ni-N平均键长为2.138,B_(12)H_(120~(-2)离子呈正二十面体构型,B-B平均键长为1.786。     

液-固界面上非镜面反射的波束位移的实验研究

采用Schlieren系统记录了在液 固界面上弱发散的超声波束的非镜面反射声场 ,并测量了界面上反射波束的波束位移 .研究的入射角θ _i扩大到在Rayleigh临界角θ _c 附近± 5°的范围 .实验发现弱发散波束的波束位移Δ是随θ _i的增加而减小的 .理论的计算表明 ,对于弱发散波束和弱会聚波束 ,Δ相对于θ _i 在θ _c 附近分别为递减函数和递增函数 .理论计算的Δ θ _i 曲线和实验点符合 .