L-Homopropargylglycine (HPG) is an amino acid analog of methionine that contains a very small modification, specifically an alkyne moiety that can be fed to cultured cells and incorporated into proteins during active protein synthesis. Detection utilizes the chemoselective ligation or “click ” reaction between an azide and an alkyne or cyclooctyne. The alkyne-modified protein is detected with either fluorescent azide or biotin azide. Detection sensitivity with these reagents in 1-D gels and Western blots is in the low femtomole range and compatible with downstream LC-MS⁄MS and MALDI MS analysis.
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