Zero-field splittings in metHb and metMb with aquo and fluoro ligands: a FD-FT THz-EPR study

Abstract

Disclaimer: The publisher's version overrides in case of any discrepancy.Combined X-band and Frequency-Domain Fourier-Transform THz-EPR (FD-FT THz-EPR) has been employed to determine heme Fe(III) S = 5/2 zero field splitting (ZFS) parameters of frozen solution metHb and metMb, both with fluoro and aquo ligands. Frequency domain EPR measurements have been carried out by an improved synchrotron based FD-FT THz-EPR spectrometer. ZFS has been determined by the field dependence of spin transitions within the mS=±1/2 manifold, for all four protein systems, and by zero field spin transitions between mS = ±1/2 and mS = ±3/2 levels, for metHb and metMb flouro-states. FD-FT THz-EPR data were simulated with a novel numerical routine based on Easyspin, which allows now for direct comparison of EPR spectra in field and frequency domain.We found purely axial zero field splittings of: D = 5.0(1) cm -1 (flouro-metMb), D = 9.2(4) cm -1 (aquo-metMb), D = 5.1(1) cm -1 (flouro-metHB) and D = 10.4(2) cm -1 (aquo-metHb).

Analysis of Magnetic Anisotropy and the Role of Magnetic Dilution in Triggering Single‐Molecule Magnet (SMM) Behavior in a Family of CoIIYIII Dinuclear Complexes with Easy‐Plane Anisotropy

“…Te mperature dependence of the in-phase (top) and out-of-phase components (bottom) of the ac susceptibility at different frequencies for 3' (Co/Zn = 1:10) measured under a1000 Oe applied dc field. Elemental analysis calcd (%) for C 25 Arrheniusplot (top inset).…”

“…Frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) spectra were measured at the FD-FT THz-EPR experiment at BESSY II, which is described in detail elsewhere. [24,25] An Hg-arc lamp was used as the source of broadband unpolarized radiation. Samples were prepared as pressed pellets containing am ixture of the compound under study and PE powder and mounted in the superconducting magnet.…”

“…[24,25] An Hg-arc lamp was used as the source of broadband unpolarized radiation. [24,25] An Hg-arc lamp was used as the source of broadband unpolarized radiation.…”

“…After 24-48 h, well-formed prismatic pink crystals of compound 1 were obtained. Elemental analysis calcd (%) for C 25…”

EPR on Biomolecules

“…This is possible with a distance matrix geometry approach 72 or with multilateration approaches 69,73 that are similar to the one used in the global positioning system. 68 Driven by technological [86][87][88][89][90] and biochemical advances, EPR spectroscopy continues to extend to new systems, such as metal centers previously considered as EPR-silent 20 or biomolecules inside cells. Structural transitions can be modeled by relying on the structure of the initial state, a limited number of constraints for the final state, and an anisotropic elastic network model.…”