MOLECULAR CONNECTIVITY MODEL FOR DETERMINATION OF PHYSICOCHEMICAL PROPERTIES OF ALPHA-AMINO-ACIDS

A molecular connectivity model for the calculation of some physicochem ical properties of a-amino acids such as molecular weights, molecular volumes, isoelectric points, relaxation times, crystal densities, solu bilities, specific rotations, and atom charges is presented. The given model, based on a set of six molecular connectivity indexes, MCI = {D , D(V), 0X, 0X(V), 1X, 1X(V)} gives a good description of all these ph ysicochemical properties, except atom charges. While calculation of is oelectric points and of solubilities requires a connectivity model cen tered on the connectivity indexes of the functional fragments of the a -amino acids, other properties, with the exception of the atomic charg es, are centered on the molecular connectivity indexes of the whole am ino acid. A subset composed of three indexes from this set gives also a rather good description of these properties. The molecular connectiv ity model of the atom charges shows a simple linear correlation betwee n atomic, delta(V) (and delta for sp3 carbons) index and atom charges, broadening thus the meaning of delta and valence delta numbers used t o describe the given set of physicochemical properties in alpha-amino acids.