The overall objective is to understand structure-function relationships of proteins, particularly snake venom toxins, and their mechanism. Snake venoms are rich sources of toxins that interfere with various physiological processes. We are specifically interested in protein families of phospholipase A2 (PLA2) enzymes, serine proteinases, three-finger toxins and helveprins. The functional diversity despite the structural similarity and the presence of functional sites in different segments of the toxins makes our research interesting and challenging. The functional sites are used in designing proteins with novel biological activities and prototypes of therapeutic agents.