title: Molecular Rationale for Improved Dynamic Nuclear Polarization of Biomembranes.
abstract: Dynamic nuclear polarization (DNP) enhanced solid-state NMR can provide orders of magnitude in signal enhancement. One of the most important aspects of obtaining efficient DNP enhancements is the optimization of the paramagnetic polarization agents used. To date, the most utilized polarization agents are nitroxide biradicals. However, the efficiency of these polarization agents is diminished when used with samples other than small molecule model compounds. We recently demonstrated the effectiveness of nitroxide labeled lipids as polarization agents for lipids and a membrane embedded peptide. Here, we systematically characterize, via electron paramagnetic (EPR), the dynamics of and the dipolar couplings between nitroxide labeled lipids under conditions relevant to DNP applications. Complemented by DNP enhanced solid-state NMR measurements at 600 MHz/395 GHz, a molecular rationale for the efficiency of nitroxide labeled lipids as DNP polarization agents is developed. Specifically, optimal DNP enhancements are obtained when the nitroxide moiety is attached to the lipid choline headgroup and local nitroxide concentrations yield an average e(-)-e(-) dipolar coupling of 47 MHz. On the basis of these measurements, we propose a framework for development of DNP polarization agents optimal for membrane protein structure determination.
authors.affiliation: Department of Chemistry, University of Florida , 214 Leigh Hall, P.O. Box 117200, Gainesville, Florida 32611, United States.|National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States.
authors.forename: Adam N
authors.initials: AN
authors.lastname: Smith
authors.affiliation: Department of Chemistry, University of Florida , 214 Leigh Hall, P.O. Box 117200, Gainesville, Florida 32611, United States.
authors.forename: Umar T
authors.initials: UT
authors.lastname: Twahir
authors.affiliation: National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States.
authors.forename: Thierry
authors.initials: T
authors.lastname: Dubroca
authors.affiliation: Department of Chemistry, University of Florida , 214 Leigh Hall, P.O. Box 117200, Gainesville, Florida 32611, United States.
authors.forename: Gail E
authors.initials: GE
authors.lastname: Fanucci
authors.affiliation: National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States.|Department of Biochemistry & Molecular Biology, University of Florida , P.O. Box 100245, Gainesville, Florida 32610, United States.
authors.forename: Joanna R
authors.initials: JR
authors.lastname: Long
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism*; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D015394:Molecular Structure; D009589:Nitrogen Oxides; D019906:Nuclear Magnetic Resonance, Biomolecular; D013113:Spin Labels
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D009589:Nitrogen Oxides; D013113:Spin Labels; C039900:nitroxyl