四环戊二烯基二苯氧基--μ-氧合二锆晶体和分子结构

四环戊二烯基二苯氧基-μ-氧合二锆([(η~5-C_5H_5)_2Zr(OC_6H_5)]_2O)晶体空间群为C2/C,晶胞参数为:a=26.103,b=8.790,c=16.097A,β=126.410°,Z=4。初结构经最小二乘修正后R因子降至0.049。结果分析给出了两个环戊二烯基平面的夹角为52.1°,锆—氧—锆桥键(Zr—O—Zr)夹角为163.7°。配合已测定分子结构的同类化合物的对应结构参数,讨论了在该类化合物中配位体对分子构型的影响及Zr—O—Zr桥键的特征。     

REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——HYDROGEN BONDS AND BOUND WATER

The hydrogen bonds in insulin fall into three cases: the helical hydrogen bonds in α- or 3_(10)helices, the non-helical one formed by polar groups of insulin itself, and the hydrogen bondsformed between insulin and water. By using the information obtained, the results of a seriesof biochemical investigations on insulin analogs related to B-chain C-terminal peptide can beinterpreted and it can also be inferred that the complex behaviours of the aggregation ofinsulin may play a protective role for the unique conformation of the molecule. Water structure also appears in the refined model. About one third of the water in anasymmetric unit is hydrogen-bonded to insulin molecules or each other, which are referred toas bound water. The polar and charged groups of insulin all show the tendencies to bind towater molecules as many as possible, which is a significant factor for the stabilization of theunique conformation of the molecule. The binding way of water molecules to insulin mole-cules is also analysed.     

REFINED CRYSTAL STRUCTURE OF INSULIN AT 1.8A RESOLUTION——CRYST

The structure of insulin has been refined by difference Fourier method at 1.8A resolu-tion. A set of computer programs calculating the mF_o-nF_c Fourier synthesis and the cor-rections of parameters automatically has been set up. With the programs to refine theinsulin model obtained from MIR map at 1.8A resolution for 11 cycles, the R index(R=∑|KF_o- F_c|/∑KF_o) is reduced to 0.210 from the initial value of 0.388. Duringthe refinement the stereochemistry of the insulin molecules is constantly detected andadjusted to fit the reasonable geometry. The refinement has greatly improved the structuremodel of insulin and provided more detailed structure information. On the basis of this thesystems of hydrogen bond in an insulin dimer are determined and the interaction betweenwater and insulin molecules in the crystal is investigated.     

精化的1.8埃分辨率胰岛素晶体结构——晶体学修正

本文用差值Fourier技术对1.8埃分辨率胰岛素结构进行了晶体学修正。建立了一套带自动增量分析的计算程序,可进行各种(mF_o—mF_c)Fourier综合。利用这套程序修正胰岛素结构11轮,R因子从0.388降到0.210。修正期间不断监测分子的立体化学状况,并根据标准值进行调整。修正结果明显地精化了胰岛素分子的结构。以此为基础,研究分析了胰岛素二聚体的氢键体系,以及晶体中水分子与胰岛素的相互作用。     

精化的1.8埃分辨率胰岛素晶体结构——氢键网络和结合水

本文研究了胰岛素晶体中的氢键网络三种情况:螺旋氢键,分子自身极性基团间形成的非螺旋氢键,以及水分子与胰岛素分子间形成的氢键。它们形成错综复杂的交互作用,对胰岛素的结构和功能具有重要意义。修正后的结构显示了较可靠的水结构信息,表明晶胞中大约三分之一的水呈结合状态,它们与胰岛素分子且彼此以氢键结合。胰岛素分子各氨基酸残基的极性和荷电基团表现出最大限度结合氢键倾向,是稳定三维结构的重要因素。