Refractive index and thickness determination in Langmuir monolayers of myelin lipids

PUSTERLA JULIO MARTÍN; GASPERINI-MALFATTI, ANTONIO; PUENTES-MARTINEZ XIMENA; CAVALCANTI, LEIDE PASOS; RAFAEL GUSTAVO OLIVEIRA

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017

0005-2736

angmuir monolayers at the air/water interface are widely used as biomembrane models and for amphiphilic molecules studies in general. Under controlled intermolecular organization (lateral molecular area), surface pressure, surface potential, reflectivity (R) and other magnitudes can be precisely determined on these planar monomolecular films. However, some physical parameters such as the refractive index of the monolayer (n) still remain elusive. The refractive index is very relevant because (in combination with R) it allows for the determination of the thickness of the film. The uncertainties of n determine important errors that propagate non-linearly into the calculation of monolayers thickness. Here we present an analytical method for the determination of n in monolayers based on refractive index matching. By using a Brewster angle microscopy (BAM) setup and monolayers spread over subphases with variable refractive index (n2), a minimum in R is search as a function of n2. In these