Quantitative study of protein association at picomolar concentrations: the lambda phage cl repressor

Abstract

A method has been developed for radiolabeling the lambda cl repressor to a specific activity sufficiently high to permit accurate quantitation of the protein in the picomolar range of concentration. Procedures are described whereby the labeled protein can be used for accurate quantitative study of the energetics of repressor assembly by large zone analytical gel chromatography. This methodology is applicable to other systems in which the stoichiometry and energetics of tightly associating DNA binding proteins are currently difficult to measure.