IFIS - LITORAL   24734
INSTITUTO DE FISICA DEL LITORAL
Unidad Ejecutora - UE
artículos
Título:
Insights About CHAPS Aggregation Obtained by Spin Label EPR Spectroscopy
Autor/es:
A.M. GENNARO; P. M. RODI; M.D. BOCCO GIANELLO
Revista:
APPLIED MAGNETIC RESONANCE
Editorial:
SPRINGER WIEN
Referencias:
Lugar: Viena; Año: 2014 vol. 45 p. 1319 - 1332
ISSN:
0937-9347
Resumen:
CHAPS is a zwitterionic surfactant derivative of bile salts, widely used in membrane protein isolation. While some studies regarding CHAPS self-aggregation suggest continuous increase in micelle size at increasing CHAPS concentration, other works point to the existence of two definite micelle types. In this work, stearic acid spin labels (5, 12, or 16-SASL) were added to CHAPS solutions to obtain information about the micellar structure using electron paramagnetic resonance spectroscopy. The spectra of 12-SASL were processed using Principal Factor Analysis, and at all concentrations they could be reproduced as linear combinations of only three fundamental spectra, the first one corresponding to free 12-SASL in aqueous solution. This fact suggests only two hydrophobic environments that host 12-SASL, assigned to primary and secondary CHAPS micelles. The relative populations of the label in each environment were obtained as a function of CHAPS concentration. Our results suggest barrel-shaped primary micelles with a minimum mean radius of 1.46 nm, and a critical micelle concentration cmcI = 4 mM. Secondary micelles are formed by aggregation of primary ones, with cmcII = 10 mM. They have several elongated hydrophobic pockets, with similar dimensions for all aggregate sizes. Our results contribute to the understanding of the mechanism of interaction of chain amphiphiles with CHAPS micelles.