title: ESR spectral analysis of the molecular motion of spin labels in lipid bilayers and membranes based on a model in terms of two angular motional parameters and rotational correlation times.
abstract: Electron spin resonance (ESR) spectral line shapes are calculated for a nitroxide spin-labeled molecule undergoing rapid restricted rotations (twisting) about its long molecular axis while simultaneously tumbling within a cone. Explicit expressions are derived for the hyperfine splittings and g-values, as well as for the secular contributions to the motionally modulated linewidths. The present model is useful for analyzing the restricted twisting and tumbling motions, and rotational correlation times, of spin-labeled molecules in bilayers. Simulated spectra compare well with experimental spectra of lecithin bilayers marked with cholestane spin label, over a wide temperature range.
mesh_terms: D002776:Cholestanes; D004578:Electron Spin Resonance Spectroscopy; D008567:Membranes, Artificial; D008956:Models, Chemical; D010080:Oxazoles; D010713:Phosphatidylcholines; D013113:Spin Labels; D013696:Temperature
chemical_list: D002776:Cholestanes; D008567:Membranes, Artificial; D010080:Oxazoles; D010713:Phosphatidylcholines; D013113:Spin Labels