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前阶段(1973—1976),我校蔡启瑞教授以固氮酶的十来种底物作为化学探针,并根据络合催化原理,直接推断N≡N,n—R—C≡N,n—R—N≡C,n—R—C≡CH等固氮酶的底物分子是按μ_3(η~2)方式配位络合在三核活性中心上的(但从当时已知的科学实验,尚未能确断活性中心究竟含一个或两个钼),并进一步推断两个这样的三核活性中心通过共用钼而骈联在一起,成为骈联双座的结构,从而提出了第一个立方烷原子簇结构的固氮酶活性中心模型。1977—1978年,又进行了两次演进,于1978年7月首先提出钼上不含有机硫配位体的骈联双座双立方烷的固氮酶活性中心模型,即“厦门模—Ⅲ型”[S Fe_3S_2(L)]Mo[(L′)S_2Fe_3S]。其中L和L′代表两个活动的配位体。这模型能较好地说明许多实验事实,并为合成铁钼辅基模拟体指出了方向(上述这一模型和“厦门模型—Ⅱ”、“福州模型—Ⅱ”的关系,详见文献[2]b和[3])。
In the former stage (1973-1976), Professor Cai Qirui from our university used ten kinds of nitrogenase as substrates and directly deduced N≡N, n-R-C≡N and n-R according to the principle of complexation catalysis N≡C, n-R-C≡CH and other nitrogenase substrate molecules according to μ_3 (η ~ 2) mode complexation in the trinuclear active center (but from the known scientific experiments, yet Failed to determine whether the active center contains one or two molybdenum) and further infer that two such trinuclear active centers are linked together by sharing molybdenum to become a double-stranded structure, thereby proposing the first cube Alkane cluster structure of nitrogenase activity center model. From 1977 to 1978, two further evolutions were made. In July 1978, a nitrogenase-active central model of chiral tandem bis-alkane with molybdenum without organic sulfur ligand was first proposed, namely “Xiamen model-Ⅲ ”[S Fe_3S_2 (L)] Mo [(L ’) S_2Fe_3S]. Where L and L ’represent two active ligands. This model can give a good explanation of many experimental facts and point out the direction for synthesizing iron-molybdenum-based mimetics (the relation between this model and “Xiamen Model-Ⅱ” and “Fuzhou Model-Ⅱ” ] b and [3]).