1. Department of Theoretical Chemistry, Chemical Centre, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden
2. Department of Biochemistry and Molecular Biology, Shantou University Medical College, Shantou 514041, Guangdong, PR China
3. Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium