CHAOTROPIC SOLVENTS INCREASE THE CRITICAL MICELLAR CONCENTRATIONS OF DETERGENTS

Monomer detergent concentrations of Triton X-100, Chaps amidopropyl)-d imethylammonio]-1-propanesulfonate), and sodium dodecyl sulfate in gua nidine hydrochloride, formamide, and urea solutions were measured by a n ultrafiltration procedure. This simple and rapid procedure effective ly separated the monomer forms of these detergents from their respecti ve micelle forms. Critical micellar concentrations of these detergents in water measured by this procedure agreed well with previously repor ted values. Both ionic and nonionic chaotropic agents, e.g., guanidine hydrochloride, formamide, and urea, are demonstrated to significantly shift the equilibrium between the monomer and the micellar form of va rious detergents toward the direction of monomer in a concentration-de pendent manner. Thus, monomer/micelle ratio of detergents in solution can be manipulated over a wide range by the concomitant use of chaotro pic solvents. This has direct applications in experiments involving de struction of biomembranes and solubilization of hydrophobic molecules in aqueous solutions. (C) 1995 Academic Press, Inc.