Schroeder E, Wollmer A, Kubicki J, Ohlenbusch H D
Biochemistry. 1976 Dec 28;15(26):5693-7. doi: 10.1021/bi00671a002.
The effect of proton concentration upon the subunit dissociation of horse methemoglobin has been investigated at two ionic strengths by light scattering photometry at 700 nm. Differential refractometry revealed a slight but systematic decrease of the specific refractive index increment with decreasing protein concentration for solutions in dialytic equilibrium with the solvent. In the pH range 4.8-7.2 the dissociation can be described by a simple equilibrium between tetramers and dimers. The dissociation constant Kd of the met derivative is found to be very similar to those of the O2- and CO-ligated states. From the slope of a plot of log Kd vs. pH, the number of protons bound is n = 1.3 +/- 0.1 resulting from an increase in the pK values of two groups upon dissociation. These two groups must be identical because the dissociation is symmetrical.
通过700nm的光散射光度法，在两种离子强度下研究了质子浓度对马高铁血红蛋白亚基解离的影响。示差折射法显示，对于与溶剂处于透析平衡的溶液，随着蛋白质浓度的降低，比折射增量略有但有系统地下降。在pH值4.8 - 7.2范围内，解离可以用四聚体和二聚体之间的简单平衡来描述。发现高铁衍生物的解离常数Kd与O2和CO结合态的解离常数非常相似。从log Kd对pH的图的斜率来看，结合的质子数为n = 1.3±0.1，这是由于解离时两组的pK值增加所致。这两组一定是相同的，因为解离是对称的。
