1. INPAC institute for Nanoscale Physics and Chemistry and Quantum Chemistry Group of K. U. Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium, Laboratory for Medicinal Chemistry, K. U. Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium, and Centre for Bioinformatics, School of Life Sciences, Pondicherry University, Puducherry 605014, India