title: Spin-diffusion couples proton relaxation rates for proteins in exchange with a membrane interface.
abstract: Changes in nuclear spin-lattice relaxation rates that are induced by a freely diffusing paramagnetic relaxation agent are examined for a protein in solution and compared to the case where the protein binds to a membrane. In the solution case, the intramolecular cross-relaxation rates are modest and large differences are observed in the oxygen induced protein-proton relaxation rates. In the case where a dynamic equilibrium between solution and membrane-bound environments is established, the intramolecular (1)H cross-relaxation rates for the protein protons increase dramatically because of the slow reorientational motion in the membrane-bound environment. As a consequence, all protein protons relax with nearly the same spin-lattice relaxation rate constants when bound to the membrane, and site specific relaxation effects of the diffusing paramagnet are suppressed. Slowly reorienting sites or rotationally immobilized sites sampled by observable molecules in vivo will demonstrate similar relaxation leveling effects.
authors: Department of Chemistry and Biophysics Program, The University of Virginia at Charlottesville, Charlottesville, VA 22904-4319, USA.
authors: Anshu
authors: A
authors: Bhowmik
authors: Jeffrey F
authors: JF
authors: Ellena
authors: Robert G
authors: RG
authors: Bryant
authors: David S
authors: DS
authors: Cafiso
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004058:Diffusion; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008051:Lipid Bilayers / Q000737:chemistry*; D008567:Membranes, Artificial; D008956:Models, Chemical; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D013113:Spin Labels
chemical_list: D008051:Lipid Bilayers; D008567:Membranes, Artificial; D011506:Proteins; D011522:Protons; D013113:Spin Labels