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:
GARAY, A. SERGIO; HERRERA, FERNANDO E.; PRUVOST, PAULA; BARCAROLO, DAIANA; RODRIGUES, DANIEL E.
Lugar:
Santiago del Estero
Reunión:
Congreso; Reunión Anual SAB 2015, Sociedad Argentina de Biofísica; 2015
Institución organizadora:
Sociedad Argentina de Biofísica
Resumen:
p { margin-bottom: 2.12mm; }The nondenaturingzwiterionic detergent CHAPS(3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate) isfrequently used to extract intrinsic proteins from mammalian cellswith mild perturbations of their native activity. EPR spectroscopyhad been used to characterize their micelles spin-labeled by n-SASL.We present in this work a study of the structure and dynamics ofCHAPS micelles labeled with n-SASL using Molecular Dynamicssimulations. The rotational dynamics of the doxyl moiety of then-SASL molecule determines the EPR spectra, therefore it is relevantto investigate how it is affected by the motion of the micelle as awhole and the degrees of freedom of the labeled molecule.We performedseveral MD simulations of micelles of 14 CHAPS with one of the n-SASLspin labels (n=5,12,16) solvated in water. The simulations have beenstarted from a solution of CHAPS molecules and the n-SASL distributeduniformly in the system. Long simulations (>400ns) have been runfor each n to allow for the formation of the micelles and theequilibration of their components. The arrival to the equilibriumhave been followed by calculating the temporal evolution of thegyration radii tensor, and the radial distributions of the CO2, n-Cand C18 groups of the n-SASL referred to the center of mass of themicelle in consecutive time intervals. The rotationaldynamics of the micelle as a whole can be characterized as a normaldiffusive regime whose correlation time are in the interval 1.4ns(n=5) to 7.3ns (n=16) and correlate well with their gyration radii.The rotational dynamics of the doxyl ring follow instead asub-diffusive regime with a power similar for all n, but withdifferent time scales 1.0ns (n=5), 1.2ns (n=12) and 0.2 (n=16). Thedifferences in these values can be explained by the interactions ofthe moieties of the n-SASL with the CHAPS molecules and the solvent.We explore the relevance of the specie of the spin label molecule indetermining the shape of the micelle.