Crosslinking reagents and methods for using the same for analysis of protein-protein interactions, are provided. The crosslinking reagents include a trifunctional scaffold that links two protein linking groups to each other and branches to link an affinity tag, where the protein linking groups can be fragmented from the scaffold. The distance between the two protein linking groups can be selected to crosslink two proteins of a protein complex via accessible amino acid residues. Also provided are crosslinked polypeptide compounds and kits that include crosslinking reagents. These reagents and methods find use in a variety of applications in which crosslinking of proteins in desired.