1. Protein Modelling Group MTA-ELTE, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518, Budapest 112, Hungary, Department of Medical Chemistry, University of Szeged, Dóm tér 8, Szeged, H-6720, Hungary, Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518, Budapest 112, Hungary, and Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518, Budapest 112, Hungary