Role of hydration and confined water in the adsorption of amino acids to lipid surfaces

E. A DISALVO; H ALMALECK; A.M. BOUCHET; R DIAZ; MA FRIAS; A HOLLMANN; F. LAIRION; F. MARTINI

Rusia

Congreso; Conferencia.XIV International Conference on Surface Forces. 2010; 2010

The kinetic results of the interaction of water soluble proteins or isolated aminoacids, followed by the variation of the surface pressure in time after injection in the subphase, can be described in a sequence of stages in which the structural relaxation coupled to the diffusion is evidenced by the departure from the linearity predicted from a fickean process. The relaxation of the lipid matrix is interpreted in terms of the disturbance caused in the bilayer structure by the location of the aminoacids at different regions of the bilayer. In consonance with the zeta and dipolar potential measurements, FTIR spectra obtained in PCs´ bilayers show that aminoacids such as Arg and its derivatives are inserted in the lipid environment forming strong well oriented H-bonds with the phosphate groups [1]. The interpretation of the curves allow us to conclude that the interphase region behaves as a bidimensional solution in which solute adsorption/partition causes an osmotic stress in relation to the reorganization of hydration water around the polar heads and the water confined between the chains [2]. In addition, the osmotic stress imposed by the solute partition induces changes in the molecular conformation of the lipid components in relation to its exposure to the aqueous phase as monitored by infrared spectroscopy [3]. The variation of interfacial hydration -as arise from changing the lipid head group structure from the progressive methylation of the ethanolamine from PE to PC’s dramatically alter the surface polarity and functional properties of lipid bilayer membranes in relation to aminoacid partition. [1] A. Bouchet, F. Lairion, E. A Disalvo, Biochim. Biophys. Acta, (2009) doi:10.1016/j.bbamem. 2009. 10.019. [2] E. A. Disalvo, F. Lairion, F. Martini, E. Tymczyszyn, M. A. Frías, H. Almaleck, Gordillo, G., Biochim. Biophys. Acta. 1778 (12) (2008): 2655. [3] M. A. Frías, E. A. Disalvo, Langmuir (2009) 25 (14) 8187. Acknowledgements: The authors are grateful to Dra. Monica Pickholz for critical reading and discussion.