Calculating partition coefficients of peptides by the addition method

A new addition method is described in this study for calculating the partit ion coefficients of peptides. LogP and logD values of peptides are calculat ed by summing the contributions of the component amino acids. The final mod els are derived from a multivariate linear regression analysis of 219 pepti des with known experimental data. The standard errors in a leave-one-out cr oss-validation are 0.23 and 0.24 log units for the logP and logD values, re spectively. The predictive ability of the model is tested by an extra set o f ten peptides, and the self-consistency of the model is further demonstrat ed by a new validation procedure called the evolution test. The parameters obtained in regression could be used as hydrophobicity scales for amino aci ds. The application of such hydrophobicity scales has also been discussed.