title: Distance measurements on a dual-labeled TOAC AChR M2δ peptide in mechanically aligned DMPC bilayers via dipolar broadening CW-EPR spectroscopy.
abstract: A membrane alignment technique has been used to measure the distance between two TOAC nitroxide spin labels on the membrane-spanning M2δ, peptide of the nicotinic acetylcholine receptor (AChR), via CW-EPR spectroscopy. The TOAC-labeled M2δ peptides were mechanically aligned using DMPC lipids on a planar quartz support, and CW-EPR spectra were recorded at specific orientations. Global analysis in combination with rigorous spectral simulation was used to simultaneously analyze data from two different sample orientations for both single- and double-labeled peptides. We measured an internitroxide distance of 14.6 Å from a   dual TOAC-labeled AChR M2δ peptide at positions 7 and 13 that closely matches with the 14.5 Å distance obtained from a model of the labeled AChR M2δ peptide. In addition, the angles determining the relative orientation of the two nitroxides have been determined, and the results compare favorably with molecular modeling. The global analysis of the data from the aligned samples gives much more precise estimates of the parameters defining the geometry of the two labels than can be obtained from a randomly dispersed sample.
authors.affiliation: Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, United States.
authors.forename: Harishchandra
authors.initials: H
authors.lastname: Ghimire
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Hustedt
authors.forename: Indra D
authors.initials: ID
authors.lastname: Sahu
authors.forename: Johnson J
authors.initials: JJ
authors.lastname: Inbaraj
authors.forename: Robert
authors.initials: R
authors.lastname: McCarrick
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Mayo
authors.forename: Monica R
authors.initials: MR
authors.lastname: Benedikt
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Lee
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Grosser
authors.forename: Gary A
authors.initials: GA
authors.lastname: Lorigan
mesh_terms: D000595:Amino Acid Sequence; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers / Q000737:chemistry*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D011978:Receptors, Nicotinic / Q000737:chemistry*
chemical_list: D003497:Cyclic N-Oxides; D008051:Lipid Bilayers; D010455:Peptides; D011978:Receptors, Nicotinic; D004134:Dimyristoylphosphatidylcholine; C037109:2,2,6,6-tetramethylpiperidine-N-oxide-4-amino-4-carboxylic acid