Economidou J, Hughes-Jones N C, Gardner B
Immunology. 1967 Sep;13(3):227-34.
The rate constants for association and dissociation, and the equilibrium constants, were determined for I-labelled anti-A and anti-B of both IgG and IgM molecular types. The following results and conclusions were obtained: 1. The equilibrium constants were within the range 06×10–13.0×10 l/mole, and were of the same order for both IgG and IgM antibodies. 2. The initial rate constants for association were in the range 2.1×10–4.8×10 l/mole/sec, and the energy of activation () 6700–9000 cal/mole. These results indicate that the rate of association is approaching the limit set by the rate of diffusion of the reactants. 3. The initial rate constants for dissociation were 1 × 10–5 × 10/sec and = 20,000–36,000 cal/mole. These latter values suggest that more than one bond must be broken simultaneously during dissociation. 4. Ionic strength and pH changes have only a minor effect on the constants; this indicates absence of ionic groups on A and B antigen sites. 5. The changes in enthalpy were –5400 to –21,800 cal/mole; the reactions are mainly enthalpy driven and this accounts for the fact that anti-A and anti-B agglutination titres increase as the temperature is decresed. 6. There was heterogeneity of the values of the standard change in free energy, enthalpy and entropy within each example of antibody. 7. The approximate concentrations of antibody at the end-points of the agglutination titres were: for IgG antibody, 0.2 μg/ml; for IgM antibody, 0.01 μg/ml.
测定了IgG和IgM分子类型的I标记抗A和抗B的结合速率常数、解离速率常数和平衡常数。得到以下结果和结论：1. 平衡常数在06×10–13.0×10 l/摩尔范围内，IgG和IgM抗体的平衡常数处于同一数量级。2. 结合的初始速率常数在2.1×10–4.8×10 l/摩尔/秒范围内，活化能（）为6700–9000卡/摩尔。这些结果表明结合速率接近反应物扩散速率所设定的极限。3. 解离的初始速率常数为1×10–5×10/秒，活化能为20,000–36,000卡/摩尔。后一组值表明解离过程中必须同时断裂多个键。4. 离子强度和pH变化对这些常数只有轻微影响；这表明A和B抗原位点上不存在离子基团。5. 焓变在–5400至–21,800卡/摩尔之间；反应主要由焓驱动，这就解释了抗A和抗B凝集效价随温度降低而升高的事实。6. 每种抗体实例中自由能、焓和熵的标准变化值存在异质性。7. 凝集效价终点时抗体的近似浓度为：IgG抗体为0.2微克/毫升；IgM抗体为0.01微克/毫升。
