Protein identification by 3D OrbiSIMS to facilitate in situ imaging and depth profiling.

Kotowska, Anna M; Trindade, Gustavo F; Mendes, Paula M; Williams, Philip M; Aylott, Jonathan W; Shard, Alexander G; Alexander, Morgan R; Scurr, David J · Nat Commun · 2020

basic_science · Level V

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Abstract

Label-free protein characterization at surfaces is commonly achieved using digestion and/or matrix application prior to mass spectrometry. We report the assignment of undigested proteins at surfaces in situ using secondary ion mass spectrometry (SIMS). Ballistic fragmentation of proteins induced by a gas cluster ion beam (GCIB) leads to peptide cleavage producing fragments for subsequent Orbitrap<sup>TM</sup> analysis. In this work we annotate 16 example proteins (up to 272 kDa) by de novo peptide sequencing and illustrate the advantages of this approach by characterizing a protein monolayer biochip and the depth distribution of proteins in human skin.

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