Affinity labeling of anti-lactose antibodies with bromoacetylaminolac dye in dark

Affinity labeling of rabbit IgG anti-lactose antibodies of restricted heterogeneity by bromacetylaminolac dye was carried out in dark and the label on the isolated chains determined by SDS gel electrophoresis. The pattern of labeling was compared with that obtained when the reaction was carried out in light using the same reagent. Differences were observed in the mode of labeling of chains. Possible use of mapping the active site of the antibody by the same labeling reagent which can exist in two geometrical forms under dark and light conditions is discussed.