INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Structure and dynamics of stearic acid spin label (n-SASL) on CHAPS micelles, studied by molecular dynamics simulations
Autor/es:
A. SERGIO GARAY; FERNANDO E. HERRERA; PAULA PRUVOST; DAIANA BARCAROLO; DANIEL E. RODRIGUES
Lugar:
Sierra de la Ventana, Provincia de Buenos Aires
Reunión:
Congreso; Reunión Anual Sociedad Argentina de Biofísica XLIII; 2014
Institución organizadora:
Sociedad Argentina de Biofísica
Resumen:
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Stearic
acid
spin labels (n-SASL)
with a doxyl group linked at different Cn
acyl positions (n=5,
12, 16) are usually employed to probe the dynamics of micelles by EPR
spectroscopy. The experiments using this technique applied to CHAPS
micelles, a detergent commonly used in membrane biochemistry, show
the peculiar result that the label at position 12 of the acyl chain
has a spectrum characteristic of a slower motion dynamics than those
labeled at sites 5 and 16. This fact contrast with common order
parameter profiles for other micelles or membrane systems. In
a previous work we have studied the build up, structure and dynamics
of micelles of CHAPS by Molecular Dynamic simulations (MD). To
understand the dynamics and location of the n-SASL spin labels in
CHAPS micelles, we performed several MD of the formation of
aggregates of 14 CHAPS with different n-SASL.
Starting from uniformly distributed solution, all simulations end in
the formation of micelles that comprise the n-SASL molecule. We
found that the 12-SASL molecule binds to the micelles through
interactions of its carbonyl oxygens with the polar groups of CHAPS
and also through the hydrophobic stabilization of its acyl tail that
follows the position of the doxyl moiety. In the case of 5-SASL the
carbonyl head are exposed to water and with smaller interactions with
the CHAPS polar groups. The 16-SASL binds its polar head to CHAPS but
the doxyl ring protrudes from the micelle surface. These differences
rationalize differences in the dynamics of the EPR active doxyl ring.