四羧基锰酞菁作为超氧化物歧化酶和过氧化物酶模拟酶的研究

用核黄素 蛋氨酸光照法和黄嘌呤氧化酶 细胞色素C还原法证实,在1.0×10-6～1.0×10-5mol/L范围内四羧基锰酞菁(TcPcMn)表现出良好的清除超氧阴离子自由基(O—·2)的活性;用黄嘌呤氧化酶 NBT还原法测算出的TcPcMn清除O—·2的二级反应速率常数为7.77×105mol-1·L·s-1,表明TcPcMn作为超氧化物歧化酶(SOD)模拟酶能很好的抑制O—·2的还原性.TcPcMn既能催化H2O2与4 氨基安替比林和酚的显色反应,也能催化邻苯二胺的聚合,表明TcPcMn具有过氧化物酶(POD)活性.用邻苯三酚自氧法得出,TcPcMn将O—·2的氧化性转化成了POD和H2O2的氧化性.因此只要牺牲一定的POD底物,TcPcMn就可以清除掉因歧化O—·2而产生的H2O2,继而能避免因发生Fenton反应而产生氧化性高于O—·2的羟自由基,从而彻底消除O—·2的氧化性,与SOD相比,这是TcPcMn的一个优势.     

水溶性席夫碱型锰配合物的合成、表征及其模拟超氧化物歧化酶活性研究

以水杨醛为母体, 与胺类化合物缩合形成席夫碱配体, 用分子自组装法合成了一系列水溶性席夫碱型金属锰单核、双核配合物. 通过元素分析、红外光谱对配合物进行了表征, 采用邻苯三酚自氧化法测定了配合物的超氧化物歧化酶(SOD)活性. 结果表明, 这些水溶性锰配合物具有良好的SOD活性.     

电泳中介微分析法测定超氧化物歧化酶

基于超氧化物歧化酶(SOD)对邻苯三酚自氧化的抑制作用和电泳中介微分析(EMMA)技术建立了一种测定SOD的新方法。采用“三明治”式不同pH缓冲液部分填充法,有利于邻苯三酚的自氧化反应,便于观察SOD的抑制作用,有利于反应产物与反应物的分离。对溶液填充模式、反应条件等实验参数进行了优化。在最优条件下,邻苯三酚自氧化反应的抑制率I与SOD浓度C在1.00×102~6.00×102μg/L范围内呈良好的线性关系,回归方程为:I(%)=0.0895C(μg/L) 17.633(r=0.9973)。     

Quantum chemistry investigation on the active site of Mn-SOD

In this paper, we carried out a theoretical study on the active site structures of the Mn-SOD with ab initio Hartree–Fock SCF method, and analyzed the molecular orbital energies, charges and atomic orbital contribution to the frontier molecular orbital.     

Kinetic and structural characterization of human manganese superoxide dismutase containing 3-fluorotyrosines

Incorporation of 3-fluorotyrosine and site-specific mutagenesis have been used with stopped-flow spectrophotometry and pulse radiolysis to investigate the catalytic properties of human manganese superoxide dismutase (MnSOD). All of the nine tyrosine residues in each of the four subunits of the homotetramer of human MnSOD were replaced with 3-fluorotyrosine. Previous studies showed that the crystal structures of the unfluorinated and fluorinated human MnSOD are nearly superimposable with the root-mean-square deviation for 198 -carbon atoms at 0.3 Å. However, the catalytic activity k_cat/K_m of the fluorinated MnSOD at 30 μM⁻¹ s⁻¹ was less than unfluorinated wild type at 800 μM⁻¹ s⁻¹. Comparison of the values of k_cat/K_m for fluorinated and unfluorinated wild-type andY34F MnSOD showed that this decrease for the fluorinated enzyme was in significant part due to 3-fluorotyrosine residues distant (>7 Å) from the active-site metal, not to 3-fluorotyrosine at position 34 close (5 Å) to the metal. Although many rate constants for the catalysis are decreased by this fluorination, the rate of dissociation of the product-inhibited complex appears unchanged by the presence of fluorinated tyrosines. These results suggest that Tyr34 is not a proton donor in the release of the product-inhibited complex, which involves protonation of a peroxo complex of the metal with release of hydrogen peroxide.     

Biological Activity of Flavonoids Copper Complexes

Three flavonoid copper(II) complexes Cu₂(quercetin)(CH₃COO)₃(CH₃OH) ( 1 ), Cu(anthrarufin)(CH₃COO)·1/2H₂O ( 2 ) and Cu(naringin)(OCH₃)(CH₃OH)₂ ( 3 ) have been synthesized and characterized by elemental analysis, IR, electronic absorption and EPR (X‐band) spectroscopy. The complexes have a strong protective action over the Δsod1 mutant of S. cerevisiae against reactive oxygen radicals generated by an external source of free radicals (H₂O₂ or the superoxide‐generating, menadione). On the other hand, the complexes cleave DNA efficiently even in the absence of reducing agents. The main reactive oxygen species responsible for the DNA strand cleavage have been determined using radical scavengers. A probably mechanism of the DNA damage is proposed.     

铜锌超氧化物歧化酶的金属重组酶的活性部位与组氨酸的相互作用

应用核磁共振和电子自旋共振技术研究了铜锌超氧化物歧化酶（ＣｕＺｎＳＯＤ）的金属重组酶与水溶液中游离组氨酸（Ｈｉｓ）的相互作用。发现在水溶液中ＣｕＺｎＳＯＤ的金属重组酶活性中心的金属可与加入的Ｈｉｓ发生作用而被部分地诱导出来，与Ｈｉｓ形成络合物。     

微透析高效液相色谱法研究金属酶与小分子的相互作用

将微透析（microdialysis)高效液相色谱法（high performance liquid chromatography,HPLC)联用技术应用于定量研究超氧化物歧化酶（superoxide dismutase)与组氨酸和组氨酸－金属离子配合物的相互作用。实验结果表明： Cu2Zn2SOD酶不仅与组氨酸，而且还可以与组氨酸－Co(Ⅱ）和组氨酸－Ni(Ⅱ)相互 作用，Cu2Zn2SOD酶中的部分Cu(Ⅱ)和Zn(Ⅱ)被诱导和置换出来，并相应地影响了 酶的活性；组氨酸－金属离子配合物的作用比组氨酸强，酶活性降低也更明显；酶 中结合的外来金属离子的量比从酶上被诱导和顶替下来的金属离子的量要少，说明 在溶液中有脱辅基酶的存在。     

Dimer asymmetry in superoxide dismutase studied by molecular dynamics simulation

Summary Molecular dynamics (MD) simulations of 100 ps have been carried out to study the active-site behaviour of the Cu,Zn superoxide dismutase dimer (SOD) in water. The active site of each subunit was monitored during the whole simulation by calculating the distances between functional residues and the catalytic copper. The results indicate that charge orientation is maintained at each active site but the solvent accessibility varies. Analysis of the MD simulation, carried out by using the atomic displacement covariance matrix, has shown a different intra-subunit correlation pattern for the two monomers and the presence of inter-subunit correlations. The MD simulation presented here indicates an asymmetry in the two active sites and different dynamic behaviour of the two SOD subunits.     

钴配合物的合成晶体结构及活性研究

The complex [Co₂Cl₂(EGTB)]·(ClO₄)₂·5H₂O was synthesized in methanol-aqueous solution and its crystal structure was determined by X-ray diffraction method. The crystal belongs to monoclinic with space group of P2₁/c. The cell parameters are a=1.42231(2)nm,b=2.53181(3)nm,c=1.43392(2)nm,β=102.0518(5)°, Z=4, F(000)=2360,D_c=1.508g·cm^-3, The final R=0.0788,wR₂=0.232, The catalytic rate constant of the dismutation of superoxide radicals has been obtained by means of photo reduction of nitroblue tetrazolium(NBT),and it is 1.875×10⁶mol^-1·L·s^-1.