Post-translational modifications (PTMs) are ubiquitous chemical alterations that are made to proteins after ribosomal synthesis. The vast number of potential PTMs that can be installed on a specific protein leads to an explosion of structural diversity, with each isoform possessing potential variation in structure and function. This has led to significant interest in proteins bearing PTMs for use as pharmaceuticals. Unfortunately, the non-templated nature of the PTM process in vivo leads to heterogeneous mixtures of isoforms that hinders the ability to study the role of a single modification in a meaningful way. We have developed a number of technologies for the efficient chemical assembly of peptides and proteins bearing homogeneous PTM patterns for the in depth interrogation of biological activity. Highlights of our recent work will be discussed in this talk, including the application of these technologies in the synthesis of several homogeneously modified bioactive proteins.