Figure 4: Cross-linking reagents commonly used in PPI studies. Cross-linker selection: depending on the analytical task at hand, a cross-linker is chosen based on its length and physico-chemical properties (left panel). A variety of cross-linking reagents are commercially available (middle panel). Custom-synthesized crosslinkers include MS-labile groups, affinity handles, and conjugation-chemistry handles for facilitating detection and purification are shown in the right panels.