Conformation of Jojoba oil esters at the air-water interface

MARTINI, FLORENCIA; BENJAMÍN CARUSO; MARÍA ANGÉLICA PERILLO; PICKHOLZ, MÓNICA

San Miguel de Tucumán

Congreso; : XLV Reunión Anual de la Sociedad Argentina de Biofísica, III Latin American Federation of Biophysical Societies (LAFeBS) y IX IberoAmerican Congress Of Biophysics.; 2016

Sociedad Argentina de Biofísica. Latinamerican Federation of Biophysical Societies

Waxes are esters (WE) of long-chain fatty acids and long-chain primary alcohols. They are highly abundant in nature (providing energy storage, buoyancy or preventing dessication) and widely used in many technological applications. Studies on their interfacial behavior are scarce and has been focused on WEs with saturated chains (thus in solid state) which do not form stable monolayers. Previously, we evaluated the ability of WE from ?jojoba oil? (JO) to form monomolecular layers and we associated it with the hypothetical configuration acquired by the long alkyl chains at the air-water interface. Thus, we proposed that, in the solid phase, WEs exhibited a linear configuration whereas in the fluid state it adopted a hairpin structure with an amphipathic-driven orientation, being this one the structure organizable like compressible monolayers. Such hypothetic configurations were derived just from molecular area measurements. In the present work we contributed with further experimental evidences by combining Langmuir isotherms, measurements of surface potential, PM-IRRAS analysis of JO and atomic-scale molecular dynamic simulations of an ether representative of WE. The surface potential (SP) of the monolayers during compression exhibited a pattern similar to that of most glycerophospholipids. The maximal SP, derived from a model that considered two populations of oriented water, was very close to the experimental value. The orientation of the ester group that was assumed in that calculation was coherent with the PM-IRRAS behavior of the carbonyl group with the C=O oriented towards the water and the C-O lying along the surface and were in accordance with their orientational angles (45° and 90°, respectively) determined by atomic-scale molecular dynamic simulations. Taken together the present results confirm a hairpin configuration of WE at the air-water interface