Cross linkers are used for the identification of near-neighbour protein relationships and ligand-receptor interactions. Homobifunctional, amine-reactive NHS esters or imidates, and heterobifunctional, amine-reactive, photoactivatable phenyl azides are the most commonly used crosslinkers for these applications.

Thermo Scientific Pierce SM(PEG)n is a series of amine-to-sulfhydryl crosslinkers that differ in length from 17,6 to 95,2 angstroms as a result of polyethylene glycol spacer arms containing n equals 2 to 24 ethylene glycol units.