Surface properties of new virginiamycin M1 derivatives

Three kinds of derivatives of the M1 factor of virginiamycin have been synthesised: esters with long chain fatty acids, oximes with modified polar amino acids and bis-derivatives with both the ester and oxime function. The study of the surface tension time dependence of M1 and its derivatives has shown that it is necessary to enhance simultaneously the hydrophobicity and the hydrophilicity of M1 to render M1 surface-active. A structure/function relationship study of the surface-active bis-derivatives has shown that enhancing the hydrophobicity of the molecule led to slower adsorption kinetics, higher stability of the monolayers formed and a better capacity to penetrate a membrane model. The repulsive electrostatic forces due to the presence of charges on the amino acids linked to M1 lead to higher surface tensions, a greater molecular area at the interface and lower penetration into a membrane model. tudy has demonstrated that modifying systematically the hydrophobicity and hydrophilicity of a non surface-active molecule allows the production of surface-active derivatives.