On characterization of physical properties of amino acids

For correlating selected properties of amino acids we use the variable connectivity index ¹χ^f which is obtained by generalizing the connectivity index ¹χ by introducing variable weights. The generalized connectivity index assigns to each atom a parameter yet to be determined during the regression analysis so that the standard error of estimation becomes as small as possible. Using the weights -0.65, 5.25, 0.20, and 0.50 for carbon, oxygen, nitrogen, and sulfur, respectively, we obtained a multivariate regression with the regression coefficient 0.9865, standard error of 4.73, and Fisher ratio F = 506 for partial molar volumes of amino acids.