Melittin-solid phospholipid mixed films trigger amyloid-like nano-fibril arrangements at air water-interface

ALAIN BOLAÑO *; CARUSO, BENJAMÍN *; STEFFEN B PETERSEN; PABLO RODRIGUEZ; GERARDO D FIDELIO

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2022 vol. 1864 p. 184048 - 184059

0005-2736

We used the Langmuir monolayers technique to study the surface properties of melittintoxin mixed with either liquid-condensed DSPC or liquid-expanded POPCphospholipids. Pure melittin peptide forms stable insoluble monolayers at the air-waterinterface without interacting with Thioflavin T (Th-T), a sensitive probe to detect proteinamyloid formation. When melittin peptide is mixed with DSPC lipid at 50 % of peptidearea proportion at the surface, we observed the formation of fibril-like structuresdetected by Brewster angle microscopy (BAM), but they were not observable withPOPC. The nano-structures in the melittin-DSPC mixtures became Th-T positivelabeling when the arrangement was observed with fluorescence microscopy. In thiscondition, Th-T undergoes an unexpected shift in the typical emission wavelength ofthis amyloid marker when a 2D fluorescence analysis is conducted.Even when reflectivity analysis of BAM imaging evidenced that these structures wouldcorrespond to the DSPC lipid component of the mixture, the interpretation of ATR-FTIRand Th-T data suggested that both components were involved in a new lipid-peptiderearrangement. These nano-fibril arrangements were also evidenced by scanningelectron and atomic force microscopy when the films were transferred to a micasupport. The fibril formation was not detected when melittin was mixed with the liquidexpandedPOPC lipid. We postulated that DSPC lipids can dynamically trigger theprocess of amyloid-like nano-arrangement formation at the interface. This process isfavored by the relative peptide content, the quality of the interfacial environment, andthe physical state of the lipid at the surface.