The reactions of GK-101 (N-chloroglycine) with collagen and hydroxyproline, were studied with regard to caries removal. After reaction with N-chloroglycine, collagen was analyzed for bound available chlorine by iodiometric titration, and hydroxyproline conversion to pyrrole-2-carboxylic acid was measured by they production of a red chromogen after PAB treatment. The results indicated that collagen was chlorinated by N-chloroglycine and hydroxyproline was converted to pyrrole-2-carboxylic acid after N-chloroglycine reaction. These findings tend to indicate two possible pathways of N-chloroglycine protein interaction.