Flow injection fluorometry of protein using hypochlorite-thiamine reagent.

This paper describes a flow injection protein assay based on the formation of N-chlorides. Thiamine, which gives fluorescent thiochrome on reaction with N-chlorides, is used as a reagent. The protein sample is first mixed with the carrier solution containing sodium hypochlorite to chlorinate peptide bonds. The fluorescence reagent, containing thiamine and sodium nitrite, is then delivered to the mixture; the sodium nitrite decomposes active chlorine. The assay is sensitive, reproducible, and linear over a range from 20 ng to 2 micrograms of bovine serum albumin. The fluorescence intensity reflects the correct amount of protein because the thiochrome formed is proportional to the number of peptide bonds.