Secondary structure determines the rheological properties of peptide monolayers

CARUSO, B, AMBROGGIO EE, N. WILKE, FIDELIO GD

Sierra de la Ventana

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

Sociedad Argentina de Biofísica

Understanding the rheology of interfaces covered with proteins is of a particular interest for interfacial biophysics. To date, there is no clear data on how secondary structure modulates the rheological properties of protein interfaces. Here, we study the surface rheology of two simple but different peptides: the -helix Melittin (Mel) and the -sheets Beta-amyloids (A1-40 and A1-42) by a) evaluation of their monolayers response to an oscillatory anisotropic compressive work and b) tracking of beads diffusing at the interface (microrheology) which provided higher sensibility for those monolayers presenting low shear response. A1-40/42, exhibit a marked elastic shear modulus whereas Mel monolayers exhibit no shear modulus and their microrheological shear was markedly lower than those for A1-40/42. On the other hand, it has been proposed that Mel may adopt a -sheet structure at pH 11 [1] (verified here by ATR and FT-IR measurements). Interestingly, Mel monolayers over pH 11 exhibit an increase in their microrheological shear. In all cases, the rheology scales for a typical polymer and their analysis suggest that the observed shear response is not due to steric restrictions (as it is proposed for proteins [2]). The data suggest that the interactions responsible for the marked shear of A1-40/2 monolayers are the hydrogen bonds of the -sheet structure that can form an infinite planar network at the interface. Altogether, this study shows a clear-cut difference on the rheological properties of peptide monolayers that adopt a differential secondary structure at the air-water interface