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Fig. 3 | Epigenetics & Chromatin

Fig. 3

From: Systematic quantitative analysis of H2A and H2B variants by targeted proteomics

Fig. 3

Signature peptides used to quantify H2A and H2B variants by targeted proteomics. a Strategy used to select the signature peptides and validate their compatibility with targeted proteomic analysis. The sequences of 22 H2A and 3 H2B variants were obtained from our recently published list of mouse histone variants (MS_histone_DB, [8]). In silico digestion of these sequences produced a theoretical list of peptides, which were ranked according to their computed ESPP score, predictive of their compatibility with MS analysis [41]. Fifty-five peptides were selected and further analyzed to monitor the potential presence of post-translational modifications, which could interfere with their analysis by targeted proteomics. This analysis excluded seven of them (see Table 1). Then, heavy standard peptides, 13C,15N-labeled, were synthesized and analyzed on different MS instruments (LTQ-Orbitrap Velos, QTRAP 5500) to acquire full MS/MS spectra and create spectral libraries. They were used to select up to five more intense SRM transitions for each peptide. b Selected signature peptides presented on their corresponding histone variants. They are presented as black bars and numbered according to Table 1. Histone fold domains, also called globular domains, are presented as a rectangle for each histone, surrounded by N- and C-terminal tails. H2A (orange), H2B (red), H4 (green)

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