Identifying Citrullinated Peptides in Complex Mixtures: Comparison of label-free and chemical modification methods

摘要

Peptide citrullination results in predictable accurate mass changes and increased hydrophobicity that can be used to target modified peptides in a complex mixture by using a label-free approach. Low abundance citrulline-containing peptides from bovine serum albumin (BSA) were identified after spiking in an E. coli digest at citrullination levels < 2.5% abundance of unmodified BSA peptides. Citrulline specific enrichment may be needed at lower relative abundances or in sample-limited cases. Improvements in peptide identification probability were observed for similar samples that were treated with a citrulline-specific reagent (4-hydroxy-phenylglyoxal, HPG). However, not all citrullinated peptides were identified with HPG modification.