Gaggelli E, Maccotta A, Valensin G
Department of Chemistry, University of Siena, Italy.
J Inorg Biochem. 1992 Nov 15;48(3):173-82. doi: 10.1016/0162-0134(92)84028-l.
Structural and kinetic features of the Mn(II)-Leu-enkephalin binding equilibria were delineated by measuring 13C and 1H NMR spin-lattice relaxation rates. The temperature dependence of such rates showed that some carbons were experiencing slow exchange regimes such that kinetic parameters at room temperature could be calculated (k(off) = 1400 sec-1, delta H* = 12.0 kcal/mol, delta S* = -9.9 e.u.). The paramagnetic rates of fast exchanging carbons were interpreted by the Solomon-Bloembergen-Morgan theory to provide structural parameters. The terminal carboxyl and amino groups were shown to be the binding sites. The motional correlation time (tau c = 0.6 nsec at 298 K) was calculated by measuring selective and double-selective 1H spin-lattice relaxation rates for the free peptide. The number of coordinated ligands was evaluated by considering the distance of the Leu CO in the complex at 2.54 A, as shown by molecular models. Finally, carbon-Mn(II) distances were calculated and the molecular model of the 1:1 complex was built.
通过测量碳-13和氢-1的核磁共振自旋晶格弛豫速率，描绘了锰（II）-亮氨酸脑啡肽结合平衡的结构和动力学特征。这些速率的温度依赖性表明，一些碳原子处于缓慢交换状态，因此可以计算室温下的动力学参数（解离常数k(off)=1400秒-1，活化焓ΔH* = 12.0千卡/摩尔，活化熵ΔS* = -9.9熵单位）。快速交换碳原子的顺磁速率由所罗门-布洛姆伯格-摩根理论解释，以提供结构参数。结果表明，末端羧基和氨基是结合位点。通过测量游离肽的选择性和双选择性氢-1自旋晶格弛豫速率，计算了运动相关时间（298K时τc = 0.6纳秒）。如分子模型所示，通过考虑复合物中亮氨酸羰基的距离为2.54埃，评估了配位配体的数量。最后，计算了碳-锰（II）的距离，并构建了1:1复合物的分子模型。
