“…Purified avidin was also examined by incubation of avidin and [14C]biotin assay mixtures at 80 °C for 30 min. Under these conditions, free and bound biotin equilibrates, and all binding sites would become labeled (White & Hughes, 1981). When biotin was tested over a range of avidin concentrations, no dilution of the radioactive label was observed in these experiments, indicating that the avidin chromatographic heterogeneity was not due to differences in endogenous biotin content.…”