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Updated: Aug 11, 2026

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
Automatic fitting to 'powder' EPR spectra of coupled paramagnetic species employing Feynman's theorem
Anders Lund1, Håkan Gustafsson, Jean Maruani
1Chemical Physics Laboratory, IFM, Linköping University, S-581 83 Linköping, Sweden. ald@ifm.liu.se
Abstract:
A previous automatic fitting procedure of EPR spectra has been extended with the purpose to characterise coupled paramagnetic complexes in powders and frozen solutions. The theoretical EPR spectra were obtained by matrix diagonalization of a general spin Hamiltonian. A least-squares fitting procedure using analytical derivatives of the calculated spectrum with respect to the spectroscopic, fine structure, nuclear quadrupole, electron-electron, and hyperfine coupling tensors was used to refine those parameters. The powder spectra of matrix isolated *CF3 and RCF2CF2* radicals, previously measured at low temperature, were reanalysed with this method. A theoretically modeled complex consisting of a Cu2+ ion, featuring an axially symmetric g-tensor and 63Cu hyperfine structure anisotropy, and a free radical located at different orientations, with respect to the symmetry axis of the Cu2+ ion, was examined in order to investigate the possibility to recover the magnetic parameters of the separate units and the magnetic couplings between them.
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