In the Raj Lab, we design novel chemical probes and sensors to illuminate the undruggable proteome, selectively detect posttranslational modifications (PTMs), and monitor biological metabolites. Our research program enables the discovery of protein biomarkers, development of affordable diagnostic tools for early cancer detection, and identification of endogenous protein partners to facilitate biotherapeutic synthesis. In this presentation, I will highlight our efforts toward single-molecule identification of proteins and PTMs in cells and organisms to advance understanding of biological processes, disease mechanisms, and biomarker discovery. We have developed multiple bioconjugation strategies for the selective labelling of lysine, methionine, asparagine, mono-methyl lysine, di-methyl lysine, and monomethyl-histidine PTMs, addressing critical gaps in existing technologies for protein and PTM sequencing at single-molecule and single-cell resolution.1-4 Importantly, we demonstrate the utility of these chemical approaches in identifying methyl lysine and methyl histidine PTMs at the single-molecule level using fluorosequencing technology, underscoring the potential of our methods to transform proteomic analysis with high sensitivity and accuracy.