We established a methodology for initiating cross-linking of antibodies selectively on the cell surface through intermolecular copper-free click reactions facilitated by increased effective concentrations of antibodies binding to target antigens. Upon cross-linking of tetrazine-and bicyclononyne-modified trastuzumab on the surface of HER2-overexpressing cells, increased antibody uptake and activation of intracellular signaling were observed. Our findings demonstrate that the cross-linking reaction can significantly alter the biophysical properties of proteins, activating their unique functionalities on targeted cells to realize an increased cargo delivery and synthetic manipulation of cellular signaling.

We have developed a novel method to globally monitor the enzymatic activities of biological samples based on performing the global activity analysis on a proteome separated by native electrophoresis. The study of the alteration in peptide-metabolizing enzymatic activity in colorectal tumor specimens led us to the discovery of elevated thimet oligopeptidase activity, which contributed to the faster consumption of immune-stimulating peptide neurotensin.