1. Department of Chemistry, Centre of Advanced Study Guru Nanak Dev University Amritsar 143 005 India
2. PG Department of Chemistry Khalsa College Amritsar 143 005 India
3. KU Leuven Department of Microbiology Immunology and Transplantation Laboratory of Virology and Chemotherapy Rega Institute Rega, Herestraat 49, box 1030 3000 Leuven Belgium