TY - JOUR
T1 - Bullet points to evaluate the performance of the middle-down proteomics workflow for histone modification analysis
AU - Coradin, Mariel
AU - Mendoza, Mariel R.
AU - Sidoli, Simone
AU - Alpert, Andrew J.
AU - Lu, Congcong
AU - Garcia, Benjamin A.
N1 - Publisher Copyright:
© 2020
PY - 2020/12/1
Y1 - 2020/12/1
N2 - Middle-down proteomics has emerged as the method of choice to study combinatorial histone post translational modifications (PTMs). In the common bottom-up workflow, histones are digested into relatively short peptides (4–20 aa), separated using reversed-phase chromatography and analyzed using typical proteomics methods in mass spectrometry. In middle-down, histones are cleaved into longer polypeptides (50–60 aa) mostly corresponding to their N-terminal tails, resolved using weak cation exchange-hydrophilic interaction liquid chromatography (WCX-HILIC) and analyzed with less conventional mass spectrometry, i.e. using Electron Transfer Dissociation (ETD) for analyte fragmentation. Middle-down is not nearly as utilized as bottom-up for PTM analysis, partially due to its limited reproducibility and robustness. This has also limited the establishment of rigorous benchmarks to discriminate good vs poor quality experiments. Here, we describe critical aspects of the middle-down workflow to assist the user in evaluating the presence of biased and misleading results. Specifically, we tested the use of porous graphitic carbon (PGC) during the desalting step, demonstrating that desalting using only C18 material leads to sample loss. We also tested different salts in the WCX-HILIC buffers for their effect on retention, selectivity, and reproducibility of analysis of variants of histone tail fragments, in particular replacing ammonium ion with ethylenediammonium ion in buffer A. These substitutions had marked effects on selectivity and retention. Our results provide a streamlined way to evaluate middle-down performance to identify and quantify combinatorial histone PTMs.
AB - Middle-down proteomics has emerged as the method of choice to study combinatorial histone post translational modifications (PTMs). In the common bottom-up workflow, histones are digested into relatively short peptides (4–20 aa), separated using reversed-phase chromatography and analyzed using typical proteomics methods in mass spectrometry. In middle-down, histones are cleaved into longer polypeptides (50–60 aa) mostly corresponding to their N-terminal tails, resolved using weak cation exchange-hydrophilic interaction liquid chromatography (WCX-HILIC) and analyzed with less conventional mass spectrometry, i.e. using Electron Transfer Dissociation (ETD) for analyte fragmentation. Middle-down is not nearly as utilized as bottom-up for PTM analysis, partially due to its limited reproducibility and robustness. This has also limited the establishment of rigorous benchmarks to discriminate good vs poor quality experiments. Here, we describe critical aspects of the middle-down workflow to assist the user in evaluating the presence of biased and misleading results. Specifically, we tested the use of porous graphitic carbon (PGC) during the desalting step, demonstrating that desalting using only C18 material leads to sample loss. We also tested different salts in the WCX-HILIC buffers for their effect on retention, selectivity, and reproducibility of analysis of variants of histone tail fragments, in particular replacing ammonium ion with ethylenediammonium ion in buffer A. These substitutions had marked effects on selectivity and retention. Our results provide a streamlined way to evaluate middle-down performance to identify and quantify combinatorial histone PTMs.
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U2 - 10.1016/j.ymeth.2020.01.013
DO - 10.1016/j.ymeth.2020.01.013
M3 - Article
C2 - 32070774
AN - SCOPUS:85080050585
SN - 1046-2023
VL - 184
SP - 86
EP - 92
JO - Methods
JF - Methods
ER -