Spin-labeled stearic acid behavior and perturbations on the structure of a gel-phase-lipid bilayer in water: 5-, 12- and 16-SASL.

We have studied the effect of the insertion of spin-labeled molecules n-doxyl-stearic acid (n-SASL, n = 5, 12, 16) on the structure and dynamics of a model lipid bilayer in gel-like phases using molecular dynamics simulations. We have studied the atomic density depth profiles and configurations of the labeled molecules in a host hydrated stearic acid bilayer system. We have found that the 5-SASL label positions its paramagnetic group at the water-lipid interface, and its polar head builds H bonds to neighboring lipids and to the solvent.