In Situ Detection of Protein Complexes and Modifications by Chemical Ligation Proximity Assay.

Protein function is often regulated by protein-protein interactions and post-translational modifications. Detection of these important biological phenomena in fixed biological samples could serve as an invaluable tool in biomedical research, drug development, as well as clinical cancer diagnostics and prognostics. We report here a novel methodology which utilizes unique antibody bioconjugates capable of forming proximity induced chemical ligation to enable in situ detection of proximal targets in fixed biological samples. Using this new methodology, we demonstrate in situ visualization of various protein heterodimers/complexes and post-translational modifications such as phosphorylation and ubiquitination. This new method offers high specificity, sensitivity, flexibility, and ease of use. In addition, the assay preserves critical contextual and heterogeneity information on biomarkers in clinically relevant samples.