Characterization of peptide-protein relationships in protein ambiguity groups via bipartite graphs (data set D1)

Motivation: In bottom-up mass spectrometry proteins are enzymatically digested before measurement. The relationship between proteins and peptides can be represented by bipartite graphs that can be split into connected components. This representation is useful to aid protein inference and quantification, which is complex due to the occurrence of shared peptides. We conducted a comprehensive analysis of these bipartite graphs using peptides from an in silico digestion of protein databases as well as quantified peptides. Results: The graphs based on quantified peptides are smaller and have less complex structures compared to the database level. However, the proportion of protein nodes without unique peptides and the proportion of graphs that contain these proteins increase. Large differences between the two underlying organisms (mouse and yeast) on database as well as quantitative level could be observed. Insights of this analysis may be useful for the development of protein inference and quantification algorithms. Link to preprint: https://www.biorxiv.org/content/10.1101/2021.07.28.454128v1?ct=