Labelling of Antibodies by 5-Dimethylamino-1-Naphthalene Sulfonyl Chloride, Its Effect on Antigen-Antibody Reactions

Abstract

Properties of the fluorescent dye DNS (5-dimethylamino-1-naphthalene sulfonyl chloride) for labeling proteins are described. DNS dissolved in absolute ethanol is added to the protein solution in [image]/15 phosphate buffer pH 7.4. Investigations of conditions of DNS binding to serum proteins reveal ratios of 3-4 [image]_ DNS/[image] gamma-globulin (human) and about 7 [image] DNS/[image] albumin (bovine). Dealing with the use of DNS in immunochemistry, experiments are carried out with the yeast alcohol dehydrogenase-rabbit antiserum system, measuring enzyme inhibition by the homologous antibodies. Labeling of antibodies with DNS does not affect rate of formation of antigen-antibody complex and has no influence on quantity of formed precipitate. The data suggest that DNS can be successfully applied in histochemical studies.