An interaction is detected between two proteins using chemically reactive or photo-activatable cross-linking reagents that covalently link amino acids in close proximity, followed by mass spectrometry analysis to identify the linked peptides (reviewed in PMID 37406423, 37104977). Experiments may be carried with live cells or cell lysates in which all proteins are expressed at endogenous levels (e.g. PMID 34349018, 35235311) or with recombinant proteins (e.g., PMID 28537071).

An interaction is inferred when a bait-enzyme fusion protein selectively modifies a vicinal protein with a diffusible reactive product, followed by affinity capture of the modified protein and identification by mass spectrometric methods.