INVESTIGADORES
OLIVEIRA Rafael Gustavo
congresos y reuniones científicas
Título:
A new method for the accurate determination of refractive index on Langmuir Monolayers by Reflectometry
Autor/es:
PUSTERLA JULIO MARTÍN; RAFAEL GUSTAVO OLIVEIRA
Reunión:
Congreso; XLII Reunión Anual SAB; 2013
Resumen:
Monolayers at
the air/water interface have been widely used as biomembrane models 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 (nm) still remain elusive. This
is important because its precise quantification allows for the determination of
the thickness of the film by R, for instance on a Brewster Angle Microscope
(BAM)1. The uncertainties of nm determine important errors
in the calculation of monolayers thickness that propagates non-linearly.
Here we present an analytical method for the
experimental determination of nm in monolayers based on the
principle of refractive index matching as used in bulk suspensions of liposomes2.
By using a BAM setup and monolayers spread over subphases with different and
known refractive index (ns), a minimum in R is search as a function
of ns. In these conditions, the nm is equal to the known ns.
The results shown correspond to monolayers of isolated bovine myelin and two
lipids with nm previously reported, DMPC and cerebrosides. The nm
values remain approximately constant, slightly increasing in a range of 0.005
to 0.01 upon compression. The obtained values allows for determination of
thickness.