Description H-L-Photo-Methionine HCl is a diazirine-containingmethionine amino acid and multifunctional photo-crosslinker. Its incorporation into peptides or small-molecule probes and tools allows for photoaffinity labeling of cellular targets and protein-protein interactions upon UV light (~360 nm) irradiation to form a covalent bond. This and othermultifunctional probe building blockswill continue to accelerate drug discovery research for probing cellular mechanisms, target ID/validation, and understanding traditionally undruggable targets. An Fmoc-protected version is also available as907367.