CRYSTAL STRUCTURE DETERMINATION OF MUNG BEAN TRYPSIN INHIBITOR Lys FRAGMENT-BOVINE TRYPSIN COMPLEX——MOLECULAR REPLACEMENT,ELECTRON DENSITY MAP AT 3.0 ■ RESOLUTION

The orientation and position of the trypsin molecule in the complex crystal cell mung bean trypsin inhibitor Lys fragment (MBILF)-bovine trypsin (BTRY) have been successfully determined by molecular replacement method with the model of the refined bovine trypsin molecule.Starting from the BTRY coordinates which were oriented and located in the correct azimuth and position in the complex cell according to the result from rotation function and translation function, sim-weighted Fourier map with coefficients 2|F_o|-|F_c| at 3.0 resolution was calculated.Besides the electron density which is obviously attributed to itself, in the vicinity of the active site of BTRY the dense contour levels corresponding to the MBILF and its boundary could be clearly seen in this map. The size of MBILF was approximately estimated at 15×15×25.     

THE CRYSTAL STRUCTURE OF A NOVEL INCLUSION COMPOUND——TETRAKIS

The title compound crystallizes in the space group C_5~4 with unit cell constants a=17.900 (5)A, b=18.466 (7)A, c=15.483 (4)A, β=92.78 (2)°and contains four formulaunits of MoFeS_(10)Cl_4N_4C_(34)H_(54). Intensities of 3499 independent reflections are collected withdiffractometer using MoKa radiation. The y coordinates of the Mo atoms are derived fromthe Patterson function. The parameters of the other atoms are found from successive Fourierand difference syntheses. The block-diagonal least-squares refinement for all atoms gives a final discrepancy factorR = 0.054. The result of structure analysis shows that this inclusion compound consists of threekinds of structural units and the oppositely charged complex ions [Mo(S_2CN(Et)_2)_4]~ and[FeCl_4]~- form a very interesting ionic host framework with infinite tunnels extending alongC direction and containing guest disulfide molecules PhCH_2SSCH_2Ph.     

7种浙江新记录植物

报道了发现于浙江的7种新记录植物,分别是厚叶铁线莲(Clematis crassifolia)、尾叶紫薇(Lagerstroemia caudata)、轮叶赤楠(Syzygium buxifoliumvar. verticillatum)、毛枝蛇葡萄(Ampelopsis rubifolia)、绒果梭罗(Reevesia tomentosa)、广西地海椒(Physaliastrum chamaesarachoides)和卡开芦(Phragmites karka).     

对《六年制重点中学数学教学大纲(草案)》(征求意见稿)的几点看法

《五年制中学数学教学大纲》和课本,自1978年秋试行以来,至今已有四年。它在十年浩劫后结束中学数学教学的无政府状态和实用主义方面,起到了应有的历史作用。但通过最近几年来的实践,也发现有不少问题,因此修改原大纲使之符合当前我国教学实际已是人心所向,势在必行。读了贵刊发表的《全日制六年制重点中学数学教学大纲(草案)》(征求意见稿)(以下简称“意见稿”)和张孝达同志关于(意见稿)的“几点说明”(以下简称“说明”),感到高兴。     

高维模型选择方法综述

模型选择是统计学的热点研究问题。近年来随着数据维数越来越高,传统模型选择方法的应用受到了很多制约。本文着重介绍高维模型选择的新方法,并讨论实现模型选择过程的一个重要环节,即调整参数的选取。最后文章总结归纳了未来可能的研究方向。     

含芳基噻唑糖基胍的NMR研究

通过对4种含芳基噻唑半乳吡喃糖基胍的¹H NMR谱的分析, 确证其糖苷键为β-构型, 对其一般特征进行了对比和讨论,并用¹H-¹H COSY, gHMQC, gHMBC, NOESY等2D NMR技术对它们的¹H和¹³C NMR谱峰进行了全归属.     

鹤草酚的晶体结构和分子结构

鹤草酚晶体属三斜晶系,空间群为PI,晶胞参数为a=9.901(3),b=11.195(4),c=11.752(4)Å,α=80.74(3),α=75.66(3),γ=76.46(3)°,晶胞内分子数Z=2.用SyntexP3/R3型四圆衍射仪收集到2891个独立衍射强度.以直接法SHELXTL解出晶体结构.结构参数的修正采用了块对角矩阵最小二乘法,最后得偏离因子R=5.7%.晶胞中含有d-,l-两种对映体分子,它们彼此以I连系组成外消旋体.每分子中的两个六环分别同相邻的氧共面,其双面角为14.2°.两个六环通过碳(sp³)桥相连,并由于形成分子内氢键O-H…O(分别为2.705Å和2.745Å)而限制了自由转动.