1. Department of Physics, UNESP/IBILCE, S. J. do Rio Preto-SP, CEP 15054−000, CP 136, Brazil, Department of Biochemistry, USP/FMRP, Avenida Bandeirantes 3900, BR-14049900 Ribeirao Preto, SP, Brazil, Laboratory of Molecular Biology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, 3714E16, 37 Convent Drive, MSC 4255, Bethesda, Maryland 20892, and Department of Chemistry, Kent State University, Kent, Ohio 44242