Grishin N V
Department of Pharmacology, University of Texas Southwestern Medical School, Dallas, TX, 75235, USA.
J Mol Evol. 1995 Nov;41(5):675-9. doi: 10.1007/BF00175826.
A general model for estimating the number of amino acid substitutions per site (d) from the fraction of identical residues between two sequences (q) is proposed. The well-known Poisson-correction formula q = e (-d) corresponds to a site-independent and amino-acid-independent substitution rate. Equation q = (1 - e(-2d)/2d, derived for the case of substitution rates that are site-independent, but vary among amino acids, approximates closely the empirical method, suggested by Dayhoff et al. (1978). Equation q = 1/(1 + d) describes the case of substitution rates that are amino acid-independent but vary among sites. Lastly, equation q = [ln(1 + 2d)]/2d accounts for the general case where substitution rates can differ for both amino acids and sites.
提出了一种根据两个序列间相同残基的比例（q）来估计每个位点氨基酸替换数（d）的通用模型。著名的泊松校正公式q = e^(-d)对应于一种与位点和氨基酸均无关的替换率。方程q = (1 - e^(-2d))/2d是针对替换率与位点无关但在氨基酸间有所不同的情况推导得出的，它与Dayhoff等人（1978年）提出的经验方法非常近似。方程q = 1/(1 + d)描述了替换率与氨基酸无关但在位点间有所不同的情况。最后，方程q = [ln(1 + 2d)]/2d适用于替换率在氨基酸和位点上都可能不同的一般情况。
