Fibril like structures induced in lipid/β-amyloid peptide Langmuir monolayers can be broken in the presence of gangliosides

PABLO RODRIGUEZ; BENJAMÍN CARUSO; ALAIN BOLAÑO; GERARDO D FIDELIO

San Luis

Congreso; XLVIII Reunion Anual de la Sociedad Argentina de Biofisica; 2019

Sociedad Argentina de Biofísica

Langmuir monolayers at the air-water interface is a proper technique to study theinterfacial properties of film forming peptides mixed with lipids. It allows to manipulatethe lipid/peptide mole ratio, the amount of the Peptide Covered Area (PCA), the physicalstate of the lipid and the degree of lateral compactness in a confined environment,mimicking a biological membrane interface. Using lipid/peptide monolayers we studiedthe surface properties of Aβ(1-40) Amyloid Peptide (AP) mixed with POPC lipid andgangliosides.At low peptide proportion, AP forms fibril-like structure in monolayers when mixed withPOPC phospholipid with reproducible π-Area isotherms. The maximal stability acquiredby the mixed films is within 35-40 mN.m-1 compatible with the equivalent surfacepressure postulated for natural biomembranes.Pure AP forms insoluble monolayers with high lateral stability without forming fibril-likestructures. In a liquid-expanded lipid environment (POPC:AP mixture), we observed thatboth miscibility and stability of the film depend on PCA. In the range of 2.5 % to 10 % ofPCA we observed fibril like structures. These fibril-like structures are clearly observedwith both BAM and AFM techniques. In this experimental condition, we found that GM1and total brain gangliosides break these fibril-like structures indicating a lateral fibrilsegregationimposed by the presence of gangliosides at the mixed interface. This effectis observed at 5-20 mole % of ganglioside with respect to POPC lipid. According to theliterature the effect of gangliosides on AP aggregation is controversial. In ourexperimental condition gangliosides have a disaggregating effect.