Phenyalanine lipid membrane interaction assessed by surface pressure studies

MATURANA, P.; CEJAS, J.; FRIAS, MARÍA DE LOS ANGELES; CUTRO, A.C.; HOLLMANN, A.; ANIBAL EDGARDO DISALVO

Buenos Aires- Bahia Blanca

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

Small amphyphilic molecules may partition in lipid membranes, among them, aromatic amino acids such as Tyr, Trp and Phe have an amphiphilic character due to the hydrophobicity of the indol and phenyl rings . In particular, Phe has been shown to damage thylakoid membranes at very low concentrations during freezing. Also, in liposomes, it also induces leakage and membrane fusion. Apparently, at relatively low concentrations the damage is produced on membranes under stress conditions, i.e. partial dehydration. Many amphiphilic compounds may protect membranes from oxidative stress under conditions of low water availability. Therefore, the influence of aminoacids such as Phe on the stability of membranes can be regulated by the water stress. It is well known that water/lipid ratio can be modified in lipid monolayers by changing the surface pressure. Thus, in order to evaluate the effects of Phe on the water-lipid interphase, the changes in the surface pressure of DPPC monolayers at different initial surface pressure (14mN/m; 26 mN/m and 40 mN/m). was evaluated in a Langmuir balance. The results suggest that in condensed membranes (40 mN/m), i.e. with less hydration, Phe are able to induce a decrease of the initial surface pressure, which is a consequence of the increase in surface tension congruent with an increase in water areas. It is interpreted that positioning of Phe in the lipid-water interface may produce a local condensation of lipids by interactions between head group and H bonding residues of the aminoacid. Further experiments to confirm this hypothesis were carried out at different Phe alanine concentrations and pHs.