INTERACTION OF PHENYLALANINE WITH LIPID MEMBRANES: MORE THAN A HYDROPHOBIC INTERACTION.

ROSA, A.S ; CUTRO, A.C.; DISALVO, E.A.; FRÍAS, M.A.

Santiago del Estero

Congreso; XLIV Reunión Anual SAB 2015; 2015

Sociedad Argentina de Biofísica

Phenylalanine (Phe) plays an important role in different physiological processes such as antimicrobial activity of certain peptides as clavanin, where its presence provides the peptide sufficient hydrophobicity, affinity and conformational flexibility, necessary for its action.1 In aqueous solution, Phe has a very high hidrophobicity that could influence the hydrogen bond network and its environment.2The negative free energy previously reported 3 is explained by the stabilization of a PC-Phe complex in the presence of water shown by the decrease in the PO frequency in the presence of water. An entropic contribution due to the disruption of the water network around the phenyl and in the membrane defect may be invoked. The insertion would promote spacing of the PO groups that are facing to water in the surface as shown by the frequency decrease. The dipole potential decrease is explained by the orientation of the carboxylate opposing to the CO of the lipids with oxygen moiety towards the low hydrated hydrocarbon core. The symmetric bending frequency of NH3+ group of Phe, decreases in 5.2 cm-1 in relation to water congruent with zeta potential shift to positive values. The Phe to DPPC dissociation constant is Kd = 2.22 ± 0.08 mM, from which the free energy change is about -4.54 kcal/mol at 25oC. The difference with the previously calculated value3 may be ascribed to hydrophobic contributions and two hydrogen bonds.