The scientific core of the biopharmaceutical industry is biol. chem. where, as per the ACS Biol. Chem. Division, researchers are, "using chem. to develop a better understanding of biol. processes and to harness these processes for the common good." For example, the successful practice of medicinal chem. is a multi-faceted exercise in biol. chem., the goal being to design mols. that meet demanding profiles for modulating biol. targets, pathways, cells, tissues and organs of interest while avoiding the modulation of other processes that would lead to undesired pharmacol. and while further understanding and engineering how those mols. will be themselves modulated (dissolved, absorbed, bound, transported, distributed, metabolized, excreted) upon administration to patients. This presentation will focus on case studies from academic and biotechnol. laboratories where synthetic chem. has been developed and applied to understand and improve antibiotic function and another where in vivo selection for mol. function provided interesting insights into the plasticity of enzymic catalysis.