title: EPR relaxation-enhancement-based distance measurements on orthogonally spin-labeled T4-lysozyme.
abstract: Lanthanide-induced enhancement of the longitudinal relaxation of nitroxide radicals in combination with orthogonal site-directed spin labeling is presented as a systematic distance measurement method intended for studies of bio-macromolecules and bio-macromolecular complexes. The approach is tested on a water-soluble protein (T4-lysozyme) for two different commercially available lanthanide labels, and complemented by previously reported data on a membrane-inserted polypeptide. Single temperature measurements are shown to be sufficient for reliable distance determination, with an upper measurable distance limit of about 5-6 nm. The extracted averaged distances represent the closest approach in Ln(III) -nitroxide distance distributions. Studies of conformational changes and of bio-macromolecule association-dissociation are proposed as possible application area of the relaxation-enhancement-based distance measurements.
authors.affiliation: Laboratory of Physical Chemistry, ETH Zurich, Wolfgang Pauli Strasse 10, 8093 Zurich (Switzerland).
authors.forename: Sahand
authors.initials: S
authors.lastname: Razzaghi
authors.forename: Evan K
authors.initials: EK
authors.lastname: Brooks
authors.forename: Enrica
authors.initials: E
authors.lastname: Bordignon
authors.forename: Wayne L
authors.initials: WL
authors.lastname: Hubbell
authors.forename: Maxim
authors.initials: M
authors.lastname: Yulikov
authors.forename: Gunnar
authors.initials: G
authors.lastname: Jeschke
mesh_terms: D017122:Bacteriophage T4 / Q000201:enzymology*; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D028581:Lanthanoid Series Elements / Q000737:chemistry; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D009569:Nitric Oxide / Q000737:chemistry; D013113:Spin Labels; D013696:Temperature
chemical_list: D056831:Coordination Complexes; D028581:Lanthanoid Series Elements; D013113:Spin Labels; D009569:Nitric Oxide; D009113:Muramidase
keywords: EPR; lanthanides; nanometer-range distances; nitroxide radicals; proteins