The lens is composed of highly stable and long-lived proteins, the crystallins which are divided into alpha-, beta-. and gamma-crystalline. Human gamma-crystalline belong to the betagamma superfamily. A large number of gamma-crystalline have been sequenced and have been found to share remarkable sequence homology with each other. Some of the gamma-crystalline from various sources have also been elucidated structurally by X-ray crystallographic or NMR spectroscopic experiments. Their three-dimensional structures are also similar having consisted of two domains each possessing two Greek key motifs. In this study we have constructed the comparative or homology models of the four major human gamma-crystalline, gammaA-, gammaB-, gammaC-, and gammaD-crystalline and studied the charge network in these crystallins. Despite an overall structural similarity between these crystallins, differences in the ion pair formation do exist which is partly due to the differences in their primary sequence and partly due to the structural orientation of the neighboring amino acids. In this study. we present an elaborate analysis of these charged interactions and their formation or loss with respect to the structural changes. (C) 2002 Elsevier Science (USA). All rights reserved.