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. Author manuscript; available in PMC: 2023 Oct 1.
Published in final edited form as: Curr Opin Chem Biol. 2022 Jun 29;70:102180. doi: 10.1016/j.cbpa.2022.102180

Figure 1.

Figure 1

Schematic representation of bottom-up and top-down strategies. Bottom-up methods include a proteolytic digestion step undertaken on a mixture of proteins of interest, and the resulting mixture of peptides is separated and analyzed by LC-MS/MS in which MS1 and MS/MS spectra are acquired for the eluting peptides, then evaluated using database search methods to identify proteins. Top-down approaches examine intact proteins in which a mixture of proteins is separated and analyzed by LC-MS/MS in which MS1 and MS/MS spectra are acquired for the intact proteins as they elute, thus maintaining the entire context of modifications for each proteoform.