Patent ID: 7794963

Claim:
A process for in vivo labeling and detecting a polypeptide or protein in a prokaryotic cell comprising: a) providing an unpermeabilized prokaryotic host cell comprising a chimeric genetic construct encoding a polypeptide or protein comprising at least one tetracysteine tag; b) growing the unpermeabilized prokaryotic host cell of (a) under suitable conditions to express the chimeric genetic construct and to produce the polypeptide or protein comprising said at least one tetracysteine tag; c) contacting in vivo the prokaryotic host cell of (b) with an effective amount of at least one biarsenical labeling reagent that binds to the at least one tetracysteine tag forming at least one fluorescent complex, wherein said contacting is performed in the absence of a reducing agent; and d) detecting the prokaryotic cell comprising the at least one fluorescent complex by utilizing a fluorescence activated cell sorter (FACS) to select a subpopulation of cells which display the highest fluorescence.