Surface properties of β-amyloid peptide mixed with lipids

BENJAMÍN CARUSO; ERNESTO E AMBROGGIO; NATALIA WILKE; GERARDO D FIDELIO

Santiago del Estero

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Biofisica 2015; 2015

Sociedad Argentina de Biofísica

In studies of the mechanism of action, a widespread approach is to analyse the effect of peptides on the integrity or, more in general, the mechanical properties of membranes. Proteins and lipids exhibit different rheological properties, with the former exhibiting high shear viscosity and/or elasticity (). We have found that the amyloidogenic peptide Aβ1-40 (40 aa) exhibit high  (>20 mN/m) in Langmuir monolayers. Comparatively, the 26 aa Melittin (Mel) did not exhibit shear [1]. On the other hand, while both peptides form homogeneous monolayers, their mixtures with lipids appear heterogeneous, with peptide enriched domains (Mel) and fibrillar structures (Aβ1-40). This led us to evaluate if the rheology of mixtures is governed by the continuous phase. Using macro-rheological determinations, no shear was observed even in mixtures containing high contents of Aβ1-40. The variation of compressibility of monolayers was used to identify phase transitions upon compression (Comp) / expansion (Exp) cycles. Mixtures containing Aβ1-40 exhibit phase diagrams which differ between Comp and Exp. This hysteresis can be related to the hysteresis observed in the pure Aβ1-40 monolayer, whose wComp was 2-fold wExp. Furthermore, this hysteresis wasn´t reproducible in a second Comp/Exp cycle suggesting the establishment of irreversible interactions. Contrary to Mel and other peptides that exhibit a ?lipid-like? behavior, Aβ1-40 compression isotherms present a T dependence that suggests a non zero entropy of compression. Our results are discussed in terms of the interactions that can be established between peptides at molecular at which they are faced to in natural membranes.