Green M K, Kotowycz G
Can J Biochem. 1979 Jul;57(7):995-9. doi: 10.1139/o79-123.
Magnetic resonance techniques have been applied to study the stability of the complexes formed between Mn(II) ions and NADP in aqueous solutions at a pH of 7.5 and 20 degrees C. The electron paramagnetic resonance (epr) data indicate that at low Mn(II) ion concentrations ([Mn(II)] less than 1 mM; [NADP] approximately 5 mM), a 1:1 complex is formed with an apparent stability constant K1 = 370 +/- 50 M-1 at an ionic strength of 0.22 in the presence of 0.20 M Cl-. At high Mn(II) ion concentrations, a Mn(II)2-NADP species, with an apparent stability constant K2 = 54 +/- 17 M-1, is present in significant amounts. When the epr data are corrected for the presence of the MnCl+ ion, the analysis of the new Scatchard plot yields stability constants for the two sites of K1 = 640 +/- 90 M-1 and K2 = 88 +/- 13 M-1, respectively. The presence of two metal ion binding sites on the NADP molecule has not been observed previously, and previous workers have always analyzed their data in terms of the 1:1 Mn(II)-NADP complex. An epr temperature study of K1 yields a value of delta H equal to 1.3 +/- 0.2 kcal/mol (1 cal = 4.187 J).
已应用磁共振技术研究在pH为7.5和20摄氏度的水溶液中，锰离子（Mn(II)）与烟酰胺腺嘌呤二核苷酸磷酸（NADP）形成的配合物的稳定性。电子顺磁共振（epr）数据表明，在低锰离子浓度（[Mn(II)]小于1 mM；[NADP]约为5 mM）时，在0.20 M Cl-存在下，离子强度为0.22时会形成1:1配合物，其表观稳定常数K1 = 370 +/- 50 M-1。在高锰离子浓度下，会大量存在一种表观稳定常数K2 = 54 +/- 17 M-1的Mn(II)2-NADP物种。当对MnCl+离子的存在对epr数据进行校正后，对新的Scatchard图分析得出两个位点的稳定常数分别为K1 = 640 +/- 90 M-1和K2 = 88 +/- 13 M-1。此前尚未观察到NADP分子上存在两个金属离子结合位点，且之前的研究人员一直根据1:1的Mn(II)-NADP配合物来分析他们的数据。对K1进行的epr温度研究得出ΔH值等于1.3 +/- 0.2 kcal/mol（1 cal = 4.187 J）。
