title: Internal Dynamics of the 3-Pyrroline-N-Oxide Ring in Spin-Labeled Proteins.
abstract: Site-directed spin labeling is a versatile tool to study structure as well as dynamics of proteins using EPR spectroscopy. Methanethiosulfonate (MTS) spin labels tethered through a disulfide linkage to an engineered cysteine residue were used in a large number of studies to extract structural as well as dynamic information on the protein from the rotational dynamics of the nitroxide moiety. The ring itself was always considered to be a rigid body. In this contribution, we present a combination of high-resolution X-ray crystallography and EPR spectroscopy of spin-labeled protein single crystals demonstrating that the nitroxide ring inverts fast at ambient temperature while exhibiting nonplanar conformations at low temperature. We have used quantum chemical calculations to explore the potential energy that determines the ring dynamics as well as the impact of the geometry on the magnetic parameters probed by EPR spectroscopy.
authors.affiliation: Institute of Chemistry and Biochemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Consentius
authors.affiliation: Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany.
authors.forename: Bernhard
authors.identifier: http://orcid.org/0000-0001-7928-4488
authors.initials: B
authors.lastname: Loll
authors.affiliation: Max Delbrück Center for Molecular Medicine in the Helmholtz Association , Robert-Rössle-Straße 10, 13125 Berlin, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gohlke
authors.affiliation: Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Alings
authors.affiliation: Institute of Chemistry and Biochemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Müller
authors.affiliation: Institute of Chemistry, Technische Universität Berlin , Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Müller
authors.affiliation: Department of Physics, Freie Universität Berlin , Arnimallee 14, D-14195 Berlin, Germany.|Berlin Joint EPR Laboratory, Freie Universität Berlin , 14195 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Teutloff
authors.affiliation: Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany.|Max Delbrück Center for Molecular Medicine in the Helmholtz Association , Robert-Rössle-Straße 10, 13125 Berlin, Germany.
authors.forename: Udo
authors.initials: U
authors.lastname: Heinemann
authors.affiliation: Institute of Chemistry, Technische Universität Berlin , Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kaupp
authors.affiliation: Institute of Chemistry and Biochemistry, Laboratory of Structural Biochemistry, Freie Universität Berlin , Takustraße 6, 14195 Berlin, Germany.|Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography , Albert-Einstein-Straße 15, D-12489 Berlin, Germany.
authors.forename: Markus C
authors.initials: MC
authors.lastname: Wahl
authors.affiliation: Institute of Chemistry and Biochemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany.|Berlin Joint EPR Laboratory, Freie Universität Berlin , 14195 Berlin, Germany.
authors.forename: Thomas
authors.identifier: http://orcid.org/0000-0003-0228-9189
authors.initials: T
authors.lastname: Risse
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008698:Mesylates; D008958:Models, Molecular; D010087:Oxides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry
chemical_list: D008698:Mesylates; D010087:Oxides; D011506:Proteins; D011758:Pyrroles; C013231:pyrroline; C074502:methanethiosulfonate