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化学学报
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化学学报 ›› 1992, Vol. 50 ›› Issue (11): 1129-1133. 上一篇    下一篇

研究论文

咪唑键合细胞色素C的核磁共振共振研究

邵伟平;魏金华;唐雯霞   

  1. 南京大学配位化学研究所
  • 发布日期:1992-11-15

^1HNMR double resonance study of imidazole binding to cytochrome c

SHAO WEIPING;WEI JINHUA;TANG WENXIA   

  • Published:1992-11-15

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我们用^1HNMR双共振技术测定了在pH=7.04,温度303-319K范围内咪唑键合氧化型细胞色素C的平衡常数,从Van'tHoff和Arrhenius方程得到键合的热力学常数△H=48.5kj·mol^-1,△S°=184J·mol^-1·K^-1和活化能E~a=159kj·mol^-1,并与其它血红素蛋白和模型化合物的热力学常数作了比较和讨论.用饱和转移法归属了cytc·Im的血红素环上甲基峰,首次用NMR方法确证咪唑在与氧化型cytc反应中取代了轴向Met80,形成新的Fe-N键.

关键词: 反应机理, 咪唑, 质子磁共振谱法, 细胞色素, 热力学函数, 反应热力学

Kinetic and equilibrium data for the binding of imidazole to horse heart ferricytochrome c at temperature range of 303-319 K were determine at pH = 7.04 by using 1H NMR double resonance method. From van't Hoff and Arrhenius equations, the observed thermodn. parameters for imidazole binding are DH = 48.5 kJ/mol, DS = 184 J/mol/K, Ea = 159 kJ/mol and were compared with those of other ferric hemoproteins and a model complex. The reason of lower affinity of cytochrome c for imidazole was discussed. Saturation transfer experiments were used to assign the resolved hyperfine-shifted resonances of ferricytochrome c imidazole ring methyls. That the imidazole binds to iron by displacing the axial coordinated Met 80 was confirmed by NMR.

Key words: REACTION MECHANISM, IMIDAZOLE, PROTON MAGNETIC RESONANCE SPECTROMETRY, CYTOCHROME, THERMODYNAMIC FUNCTION

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