1. Dipartimento di Scienze Chimiche, Università di Cagliari, Via Ospedale 72, 09124 Cagliari, Italy, Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden, Institute of Biochemistry, Mokslininku 12, 2600 Vilnius, Lithuania, and Camurus AB, Ideon Research Park, S-223 70 Lund, Sweden