Bioconjugation reagents most often are used with pure biomolecules to form multi-component conjugates for a designated purpose; however, they can also be used with complex biological samples to capture interacting molecules in living systems. In particular, molecules that are undergoing some type of biospecific affinity interaction within cells can be linked together and “frozen” in the act of binding to each other with the use of certain bifunctional or trifunctional crosslinking agents. The rapid reaction kinetics of certain crosslinking agents with the functional groups present on proteins and other molecules can be used to capture even low affinity or transient interactions for subsequent study. Other methods of studying protein interactions, such as the use of affinity