一种蛋白质等电点的简便计算方法

A Simple Method of Calculating Protein's PI Value

从多元酸分步电离的角度提出了计算蛋白质等电点的简便公式:pH=(pKm+pKm+1+lgs1-lgs2)/2,其中m为蛋白质可结合质子基团数,s1=1+2[KHm-]1+3K[m-H1]K2m-2+…,s2=1+2[KHm]+2+3K[m+2H]K2m+3+….选取任意pH值作为试探初始值,以后下一次试探值为上一次试探值与公式计算值的均值,当试探值与计算值相等时的pH值即为pI值,一般仅需试探几次即可得到满意结果.文章还讨论了忽略浓度较小蛋白质离子的方法.

A simple method for calculating the protein＇s PI value was presented mathematically in this paper at the viewpoint of step - dissociation of polybasic acid：pH=（pKm＋pKm＋1＋lgs1-lgs2）/2where mis number of proton - binding residues,s1=1＋2[H]/km-1＋3[H]^2/Km-1Km-2＋…,s2=1＋2 km＋2/[H]＋3 Km＋2Km＋3/[H]^2＋….A simple test procedure was used to solve the equation, that is, a random pH value is chosen first as the initial of test pH, then the new test pH is the average of the previous test pH and the output pH of the equation in the calculation. When the test pH is equal to the output pH, that is the pI value. The method of ignoring low concentration protein ions was also provided.