In the broadest sense, we would like to determine the fundamental principles from which proteins derive their function. This requires both a precise knowledge of polypeptide fold and the atomic arrangements of amino acid side chains and knowledge of the functional components of the protein and their interaction with relevant other molecules. We have initiated an investigation of monoclonal antibodies (Mab) that neutralize rhinoviruses and Mengo viruses. It has been possible to grow large and highly diffracting crystals of one antigen binding fraction (Fab) whose binding site on human rhinovirus 14 (HRV14) has been carefully mapped. It has also been possible to grow crystals of the Fab and corresponding HRV14 peptide. Suitable docking experiments may then suggest the conformational changes produced by Mab binding to cause neutralization. Studies on phosphoglucomutase (PGM) and lactate dehydrogenase (LDH) are to continue. With the availability of refined structures, we plan to study enzyme-substrate complexes for PGM and the thermophile B. stearothermophilus LDH.