title: Determination of the distance between two spin labels attached to a macromolecule.
abstract: An EPR "spectroscopic ruler" was developed using a series of alpha-helical polypeptides, each modified with two nitroxide spin labels. The EPR line broadening due to electron-electron dipolar interactions in the frozen state was determined using the Fourier deconvolution method. These dipolar spectra were then used to estimate the distances between the two nitroxides separated by 8-25 A. Results agreed well with a simple alpha-helical model. The standard deviation from the model system was 0.9 A in the range of 8-25 A. This technique is applicable to complex systems such as membrane receptors and channels, which are difficult to access with high-resolution NMR or x-ray crystallography, and is expected to be particularly useful for systems for which optical methods are hampered by the presence of light-interfering membranes or chromophores.
authors.affiliation: Department of Chemistry, Lawrence Berkeley Laboratory, University of California, Berkeley 94720, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Rabenstein
authors.forename: Y K
authors.initials: YK
authors.lastname: Shin
mesh_terms: D000595:Amino Acid Sequence; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005583:Fourier Analysis; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009589:Nitrogen Oxides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D013113:Spin Labels
chemical_list: D009589:Nitrogen Oxides; D010455:Peptides; D013113:Spin Labels