title: Pulsed electron-electron double resonance spectroscopy between a high-spin Mn(2+) ion and a nitroxide spin label.
abstract: Pulsed Electron-Electron Double Resonance (PELDOR) has attracted considerable attention for biomolecular applications, as it affords precise measurements of distances between pairs of spin labels in the range of 1.5-8 nm. Usually nitroxide moieties incorporated by site-directed spin labelling with cysteine residues are used as spin probes in protein systems. Recently, naturally occurring cofactors and metal ions have also been explored as paramagnetic spin species for such measurements. In this work we investigate the performance of PELDOR between a nitroxide spin label and a high-spin Mn(2+) ion in a synthetic model compound at Q-band (34 GHz) and G-band (180 GHz). We demonstrate that the distances obtained with high-frequency PELDOR are in good agreement with structural predictions. At Q-band frequencies experiments have been performed by probing either the high-spin Mn(2+) ion or the nitroxide spin label. At G-band frequencies we have been able to detect changes in the dipolar oscillation frequency, depending on the pump-probe positions across the g-tensor resolved nitroxide EPR spectrum. These changes result from the restricted mobility of the nitroxide spin label in the model compound. Our results demonstrate that the high-spin Mn(2+) ion can be used for precise distance measurements and open the doors for many biological applications, as naturally occurring Mg(2+) sites can be readily exchanged for Mn(2+).
authors: Goethe University Frankfurt am Main, Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, Max von Laue Str. 7, 60438 Frankfurt am Main, Germany. prisner@chemie.uni-frankfurt.de.
authors: D
authors: D
authors: Akhmetzyanov
authors: J
authors: J
authors: Plackmeyer
authors: B
authors: B
authors: Endeward
authors: V
authors: V
authors: Denysenkov
authors: T F
authors: TF
authors: Prisner
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D007477:Ions / Q000737:chemistry; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D011789:Quantum Theory; D013113:Spin Labels
chemical_list: D056831:Coordination Complexes; D007477:Ions; D008024:Ligands; D013113:Spin Labels; D008345:Manganese