Chemical Modeling of ATP-driven Electron Transport in Nitrogenase Catalyzed Reactions Ⅰ.The Studies of Complexing [Fe_4S_4(SR)_4]~(2-) Cluster with ATP Using Polarographic and Electronic Absorption Spectroscopic Methods
- 化学化工－已发表论文 
[中文文摘]将ATP加到[Fe_4S_4(SPh)_4]~(2-)的DMF-H_2O溶液中,引起[Fe_4S_4(SPh)_4]~(2-)原子簇的氧化还原电位从-1.00±0.01伏移至-1.49±0.01伏,负移490mV左右;使[Fe_4S_4(SPh)_4]~(2-)原子簇的电子吸收光谱特征吸收强度明显降低;同时加速[Fe_4S_4(SPh)_4]~(2-)与亚甲蓝的氧化还原反应,这种加速效应比ADP明显,而ADP又比AMP明显得多。根据这些实验事实,可以认为ATP能以末端的γ-PO_4基团,或γPO_4和β-PO_4基团与[Fe_4S_4(SPh)_4]~(2-)原子簇络合或螯合,引起后者的配位场增大,提高电子的输出能力。本文还讨论了ATP与[Fe_4S_4SPh)_4]~(2-)原子簇的络合方式,进而探讨了ATP在固氮酶中的结合部位和作用机理。[英文文摘]Addition of MgATP to [Fe4(SPh)4]2- DMF-H2O has been found to shift polarographic half-wave potential of the cluster complex from -1.00±0.01V to -1.49±0.01V; to suppress the electronic absorption spectral peak of at 450nm and, moreover, to speed up redox reaction between [Fe4S4(SPh)4]2 and methylene blue. This speeding-up effect of ATP was more pronounced than that of ADP, which in turn was consider ably more pronounced than that of AMP. Based on these experimental facts, it is inferred that ATP were probably complexed through the binding(or chelation)of their terminal γ PO4(or both γ PO4 and β PO4)group to the cunane cluster,resulting in an increase in ligand field acting on the cluster and thus promoting electron outflow from the cluster to the redox dye(methylene blue).Model of complexing ATP with [Fe4S4(sPb)4]2- cluster is also discussed,and then complexing site and acting mechanism of ATP being in nitrogenase are proved.