1.9分辨率三方四锌牛胰岛素晶体结构测定

牛胰岛素三方四锌晶体属三方晶系,空间群为R3,晶胞参数:a=b=80.8c=37.4,α=β=90°,γ=120°,用同晶差值法在1.9分辨率测定了它的晶体结构,并用立体化学参数制约的倒易空间最小二乘法进行了精化,最后的R因子为0.19,与标准键长的平均偏差为0.052,在此模型基础上对四锌胰岛索长效性的可能结构机理进行了讨论。     

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。     

去B链羧端七肽胰岛素晶体结构的测定

去B链羧端七肽胰岛素(DHPI)晶体中不对称单位合二个分子,空间群P2_12_12_1。运用Patterson搜索技术确定了二个分子在晶胞中的取向,联合运用平移函数和R因子搜索测定了两个分子各自在晶胞中的位置。运用生物大分子刚体最小二乘修正技术和能量极小化最小二乘制约修正精化分子的取向和位置后,在6分辨率晶体学R因子下降到0.384。初始Fourier图显示,与天然胰岛素分子相较,DHPI分子的B链N端(B1—B8)和C端(B20—B23)肽段的构象有剧列变化,但A,B链的三段螺旋及其相对配置大体保持。     

细胞色素b三相还原过程中的中间氧化反应

本文证明琥珀酸细胞色素c还原酶中细胞色素b的还原,无论用琥珀酸还是用四甲基氢醌作底物,在pH6.0—9.0范围内均呈现出三相过程。从pH6.0到pH8.0,细胞色素b的初相还原速度都快于细胞色素c_1的还原速度。b的各相速度和c_1的还原速度都随着pH增加而增加。从细胞色素b的三相变化过程和加入外源细胞色素c后的多相氧化还原过程的低温差光谱反复扫描实验中,可清楚地看到b在562nm吸收峰的出现及消失,表明了b的还原或氧化。这些结果与单波长562nm监测的结果是一致的。     

CRYSTAL STRUCTURE DETERMINATION OF DESHEPTAPEPTIDE (B24—B30)-INSULIN

Desheptapeptide (B24—B30)-insulin (DHPI), an essentially inactive insulin analog, is crystallized in space group P2_12_12_1 with two molecules in an asymmetric unit. The orientations of the molecules in the crystal cell have been determined by using Patterson search method at 6 resolution and the positions of the molecules are deduced from translation function calculation and R search at 3. resolution. After using the rigid body refinement (CORELS) further to refine the orientational and positional parameters as well as the initial energy restrained refinement (EREF) for the model, the crystallographic R valueis reduced to 0.384 at 3 resolution. The initial Fourier map shows that the B-chain N-terminal (B1—B8) and C-terminal (B20—B22)segments, compared with the native 2 zinc insulin, exhibit drastic conformational changes, but the three helices of B- and A-chains and their relative arrangement are essentially kept in DHPI.     

Studies on Long-acting Insulin:Crystal Structure of Arg-B31 Human Insulin at 2.0 Resolution

The crystal structure of Arg-B31 human insulin(ABHI), a long-acting insulin derivative, has been determined at 2.0 resolution by using X-ray diffraction analysis. The final crystallographic R factor of the structure model after the refinement is 0.189 with the bond length r. m. s deviation of 0.018 . The refined structure of ABHI showed that the conformation of B-chain C-terminal residues was more stable than that in the native molecule. A striking structural feature of ABHI was an additional ion pair formed between ArgB31 of molecule Ⅰ and Glu-B21 of molecule Ⅱ in a dimer, and three ionic bonds between the neighbouring molecules thereby appeared on the surface of ABHI hexamer.These secondary bonds generated by the insertion of the residue Arg-B31 should make the rate of dissociation of ABHI hexamer slow down when it was injected into the body and the property of protraction should be produced by a 'depot effect'. This ought to be the main structure basis of the prolonged action of ABHI. The results o     

西藏胡黄连化学成分的分离和鉴定

从西藏胡黄连中分离和鉴定了4个化合物,其中化合物1是新化合物,命名为西藏胡黄连酚苷E(Scrophenoside E),结构为(2-甲氧基-4-乙酰基)苯酚-3-β-D-吡喃葡萄糖基-6-O-(4-β-D-吡喃葡萄糖基)香草酰基-β-D-吡喃葡萄糖苷.     

THE CHARACTERISTICS AND MOTION MODEL OF INSULIN MONOMER

The extensive conformational comparisons among the determined structures of the differeat species and crystal forms of insulin and the varied insulin derivatives were performed by using the least-squares superimposition technique and the graphics technique. The results of the investigation showed that the structure of molecule I in 2Zn insulin was closer to that of the natural monomer; the conformational difference between two molecules of a dimer came out during dimerization and it was further improved and stabilized during the hexamerization and packing of hexamers in crystal; through the hinge peptides, such as A10, B4, B8, B24, B20 and B23, there was a flexible relative motion among the structural segments in the insulin molecule, and the residues at the B-chain C-terminal might have a shift of more than 10; the mobility for each residue side-chain was very different due to the different surroundings.     

2D NMR对苦味西葫芦果实中的一个三萜皂苷进行结构解析

通过核磁共振谱并结合文献对一个三萜皂苷葫芦素E 2-O-β-D-葡萄糖苷进行结构解析. 通过2D NMR(¹H-¹H COSY、HMQC和HMBC)进行了NMR全归属.