EFFECT OF AQUEOUS SUBPHASE EXCHANGE ON THE MONOLAYER CHARACTERISTICS OF VALINOMYCIN

A special construction was built for the measurement of monolayer char acteristics of surface-active substances during aqueous subphase excha nge. These measurements are important for the determination of the spe cificity and reversibility of the interactions between amphiphiles and various compounds dissolved in the aqueous subphase. No changes in th e surface pressure-molecular area isotherms were observed during dilut ion of the salt subphase underneath monolayers of fatty alcohols, such as octadecanol (i.e. no interaction). Small reversible changes found under the same conditions for monolayers of various fatty acids (for e xample docosanoic acid) are considered to be non-specific interactions . Two additional pronounced states (II and III) of valinomycin monolay ers were observed in the presence of K+, compared with Na+ that correl ates with the strong complexation between valinomycin and these cation s in bulk (specific interaction). These changes in the monolayers of v alinomycin and fatty acids are completely reversible, in contrast with the irreversible changes for catalase monolayers during aqueous subph ase exchange.