Ionic environment, thickness and line tension as determinants of phase separation in whole Purified Myelin Membranes monolayers

PUSTERLA, JULIO; HERNÁNDEZ, JUAN MARTÍN; WILKE, NATALIA; SCHNECK, EMANUEL; OLIVEIRA, RAFAEL G.

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Año: 2021 vol. 207

0927-7765

urified myelin membranes (PMM) were spread as monomolecular films at the air/aqueous solution interface, and visualized by Brewster Angle Microscopy (BAM) at different lateral pressures (π) on three specific aqueous solutions: absence of salts, physiological conditions and presence of calcium. Coexistence of Liquid-Expanded (LE) and Liquid Ordered (LO) phases persisted up to collapse in the presence of salts, whereas monolayers became homogeneous at π ≥ 35-40 mN/m when salts are absent. This PMM phase-mixing behavior in monolayers is similar to the previously reported behavior of PMM multilamellar vesicles. Reflectivities (Rp) of p-polarized light from both phases were assessed throughout the whole π -range, and film thicknesses (t) were calculated from the Rp values and measured film refractive indices (n). The LO phase was found to be more reflective and thicker than the LE phase at π ≤ 15 mN/m, but less reflective and thinner at higher π. We als