A histochemical study of the apparent deamination of proteins by sodium hypochlorite

The possible chemical mechanisms by which neutral solutions of sodium hypochlorite containing a high concentration of sodium chloride abolish the acidophilia of proteins in sections of fixed tissue are reviewed. The most probable one is the chlorination of the protein terminal amino groups, followed by the breakdown of the N-chloramine so formed into alpha-ketocarboxylic acid, nitrile or aldehyde groups. Hypochlorite solutions certainly do not deaminate tissue sections as was previously thought. Experimental evidence for the formation of relatively stable N-chloramine groups in situ and their limited conversion to aldehydes is reported. For example, the acidophilia of hypochlorite-treated sections was found to be restored after flooding them with hydriodic acid followed by the extraction of the liberated iodine with an alcohol. The significance of these experimental findings is discussed.