title: Stearic acid spin labels in lipid bilayers: insight through atomistic simulations.
abstract: Spin-labeled stearic acid species are commonly used for electron paramagnetic resonance (EPR) studies of cell membranes to investigate phase transitions, fluidity, and other physical properties. In this paper, we use large-scale molecular dynamics simulations to investigate the position and behavior of nitroxide spin labels attached to stearic acid molecules in dipalmitoylphosphatidylcholine (DPPC) bilayers. The results of these studies are potentially very important for the interpretation of EPR spectra, which rely on assumptions about the position of the label in the membrane. Additionally, we investigate the effect of chirality and ionization of the carboxyl group of the label. For a non-ionized species, we observe that spin-label molecules are even able to make flip-flop transitions between the leaflets of the bilayer. Such transitions have been previously observed only in very rare cases in molecular simulations.
authors.affiliation: Laboratory of Physics, Helsinki University of Technology, Finland.
authors.forename: Lorna
authors.initials: L
authors.lastname: Stimson
authors.forename: Lei
authors.initials: L
authors.lastname: Dong
authors.forename: Mikko
authors.initials: M
authors.lastname: Karttunen
authors.forename: Anna
authors.initials: A
authors.lastname: Wisniewska
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Dutka
authors.forename: Tomasz
authors.initials: T
authors.lastname: Róg
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers / Q000032:analysis*; D008958:Models, Molecular; D009589:Nitrogen Oxides / Q000737:chemistry; D013113:Spin Labels; D013229:Stearic Acids / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D009589:Nitrogen Oxides; D013113:Spin Labels; D013229:Stearic Acids; D015060:1,2-Dipalmitoylphosphatidylcholine; C031183:stearic acid; C039900:nitroxyl