Vishwanath C K, Easwaran K R
Biochemistry. 1982 May 25;21(11):2612-21. doi: 10.1021/bi00540a006.
Complexation of valinomycin (VM) with the divalent cation Ca2+ in a lipophilic solvent, acetonitrile (CH3-CN), has been studied by using circular dichroism and proton and carbon-13 nuclear magnetic resonance (1H NMR and 13C NMR). From analyses of the spectral data, it is concluded that VM forms a 2:1 (peptide-ion-peptide) sandwich complex with Ca2+, at low concentration of VM. At moderate concentrations of the salt, in addition to the sandwich complex, an equimolar (1:1) complex different from those observed for potassium and sodium is also observed. At very large concentrations of the calcium salt, the data suggested a complex with a conformation similar to that of the free VM in polar solvents. Possible conformations for the sandwich and the equimolar VM-calcium complexes are proposed.
利用圆二色光谱以及质子和碳 - 13核磁共振（1H NMR和13C NMR）技术，对缬氨霉素（VM）在亲脂性溶剂乙腈（CH3 - CN）中与二价阳离子Ca2+的络合作用进行了研究。通过对光谱数据的分析得出，在低浓度的VM条件下，VM与Ca2+形成了2:1（肽 - 离子 - 肽）夹心络合物。在中等盐浓度下，除了夹心络合物外，还观察到一种与钾和钠所形成的络合物不同的等摩尔（1:1）络合物。在钙盐浓度非常高时，数据表明形成了一种构象与极性溶剂中游离VM相似的络合物。文中还提出了夹心络合物和等摩尔VM - 钙络合物可能的构象。
