The renaissance in the use of peptides and proteins as therapeutic agents has led to significant demand for new technologies to rapidly and efficiently access these biomolecules, especially those bearing tailor-made modifications to maximize specificity and activity, or to probe biological function (e.g. through incorporation of post-translational modifications, nucleic acids, fluorophores and/or imaging reagents).1,2 My lab has recently developed a number of synthetic, semi-synthetic and biosynthetic technologies that enable the generation of peptides and proteins bearing homogeneous post-translational modifications at pre-determined sites.3-8 This talk will highlight these methods and their utility for the generation of clinically approved peptide therapeutics6 and proteins bearing site-specific and homogeneous post-translational modifications7-10 through peptide ligation6-8 or by late-stage modification chemistry via photocatalysis or electrochemistry.9,10 the talk will conclude with our efforts to develop novel display technologies with genetic reprogramming for the rapid discovery of high affinity modified macrocyclic peptide ligands to therapeutic targets.11,12