With alternative splicing, post-translational modifications, translation  errors, and SNP’s all contributing to the complexity of protein structures, it is becoming clearer that detailed knowledge of these proteoforms is needed to unravel the functional systems at work.  This recent paper expands on this theme and presents a clear case for proteoforms as the most meaningful representation of  proteins.

Proteoforms as the next proteomics currency, Lloyd M. Smith and Neil L. Kelleher, Science 359 (6380), 1106-1107.