REVIEW Exploring the Mechnisms of Molecular Recognition by Flavins by Ram Singh* a ), Geetanjali b ), and Cherukuri Raghavendra Babu a ) a ) Centre for Environmental Management of Degraded Ecosystems, School of Environmental Studies, University of Delhi, Delhi-110 007, India (e-mail: singh_dr_ram@yahoo.com) b ) Department of Chemistry, University of Delhi, Delhi-110 007, India The design and development of chemical models for enzymes depends on the fundamental principles observed in biological systems. Molecular recognition of flavins by various receptors has attracted attention due to their applications as chemical models for flavoenzymes. The area of molecular recognition is being investigated through research at the interface of chemistry and biology. In this review, the literature has been surveyed to provide comprehensive coverage of the synthetic methodology of different flavins and receptors and their molecular-recognition studies. Various applications of flavin ±receptor complexes have also been highlighted. Contents 1. Introduction 2. Synthesis of Flavins 3. Synthesis of Receptors 4. Molecular Recognition of Flavins by Receptors 5. Methods of Characterization for Molecular Recognition between Flavin and Receptor 6. Applications of Flavin ± Receptor Complex 7. Summary and Future Prospects 1. Introduction Molecular recognition between molecules is one of the most fundamental processes, in biology and chemistry. It may be said that, without molecular recognition, there would be no life on this world. All important biochemical processes, such as enzyme action, molecular transport, genetic information, processing, and protein assembly involve molecular recognition as an essential action. The essential point of molecular recognition is the complementarity between the receptor and substrate, which Fischer first described as a lock and key over 100 years ago [1], the lock being the molecular receptor and the key being the substrate. The recognition process is largely driven by non-covalent interactions, such as H- bonding, p-stacking, electrostatic interactions, Van der Waals forces, conformational energy, etc. , and these forces work together in concert [2 ± 14]. Molecular recognition involves selective binding of a substrate by a molecular receptor and is involved basically in two separate processes: interactions of one molecule with another and the CHEMISTRY & BIODIVERSITY ± Vol. 2 (2005) 429  2005 Verlag Helvetica Chimica Acta AG, Zürich