1. Dipartimento di Scienze Biologiche e Ambientali, Facoltà di Scienze, Università del Sannio, Via Port'Arsa, 11-82100 Benevento, Italy, and Molecular Modeling and Bioinformatics Section, Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 37, Room 5120, 37 Convent Drive MSC 4264, Bethesda, Maryland 20892-4264