Flamig D P, Parkhurst L J
Proc Natl Acad Sci U S A. 1977 Sep;74(9):3814-6. doi: 10.1073/pnas.74.9.3814.
The first-order dissociation of tetrameric HbCO to the dimer has been studied overthe pH range 10.30-11.57 in a light-scattering stopped-flow apparatus using argon-ion laser excitation. The first-order dissociation rate constant varies from 0.25 sec-1 to 24.0 sec-1over this pH interval. A semilogarithmic plot of k versus pH has a slope of 2.56 at pH 11.07, the midpoint. The pH dependence of the dissociation of the tetramer is consistent with progressive titration of alpha1-alpha2 and beta1-beta2 salt bridges. At pH 10.66, the dissociation rates of HbO2, HbCO, methemoglobin, and HbCN vary less than 20% from their mean value. A study of the dissociation kinetics as a function of protein concentration allows one to obtain both association and dissociation rate constants, and hence equilibrium constants, for the tetramer in equilibrium dimer reaction. In this manner, equilibrium constants were obtained on protein solutions with less than 15 sec of exposure to dissociating conditions.
在10.30 - 11.57的pH范围内，使用氩离子激光激发，在光散射停流装置中研究了四聚体HbCO向二聚体的一级解离。在此pH区间内，一级解离速率常数从0.25秒⁻¹变化到24.0秒⁻¹。在pH 11.07（中点）时，k对pH的半对数图斜率为2.56。四聚体解离的pH依赖性与α1-α2和β1-β2盐桥的逐步滴定一致。在pH 10.66时，HbO₂、HbCO、高铁血红蛋白和HbCN的解离速率与其平均值的差异小于20%。对解离动力学作为蛋白质浓度函数的研究，使得人们能够获得四聚体与二聚体平衡反应中的缔合和解离速率常数，从而得到平衡常数。通过这种方式，在蛋白质溶液暴露于解离条件不到15秒的情况下获得了平衡常数。
