Top-Down Protein Sequencing by Mass Spectrometry, Quo Vadis?

Ira Krull, Analytical Chemistry, Ira Krull Associates, North Easton, MA, USA

The use of MS to characterize peptides and proteins has become the most useful, practical and applied analytical method today, though MS can be used in numerous formats. The use of wet chemistry methods has almost disappeared. This talk will deal mainly with top-down sequencing in MS (TDS), though there are several other MS approaches for already-purified proteins, such as bottom-up, middle-out, middle-down or variations thereof. So long as each, individual protein goes into the instrument, in theory, it should today be possible to perform, 100% TDS on almost any-sized molecule. Though there are many research groups around the world, as well as perhaps all MS instrument vendors, attempting to demonstrate 100% coverage for all proteins, not all efforts today meet with success. And, often the larger the protein, in terms of MW, the less likely that protein will undergo 100% sequencing, under any MS conditions. Though some in academia appear able to 100% sequence any protein of any size, and though their publications appear to support that claim, other interested parties do not appear able to replicate such work? How can MS be applied, by anyone similarly trained, to provide 100% sequence coverage of any MW protein and its variants?