Esr900 helium flow cryostat

UV-visible absorption spectra were recorded with an Uvikon XL spectrophotometer (BioTek Instruments). ⁵⁷Fe-Mössbauer spectra on purified proteins were recorded using 400 μl cuvettes containing 0.38–1.1 mM protein. Spectra were recorded on a spectrometer operating in constant acceleration mode using an Oxford cryostat that allowed temperatures from 1.5 to 300 K and a ⁵⁷Co source in rhodium. Isomer shifts are reported relative to metallic iron at room temperature. EPR spectra of purified proteins (250–500 μM) were obtained after reduction for 10 min with 1 mM dithionite prepared in buffer F (0.1M Tris-HCl pH 8) or for 40 min with 50 mM DTT prepared in buffer F. Spectra were recorded on a Bruker EMX (9.5 GHz) or ER200D EPR spectrometers equipped with an ESR 900 helium flow cryostat (Oxford Instruments). Double integrals of the EPR signals and spin concentration were obtained through the Win-EPR software using the spectrum of a 200 μM Cu(EDTA) standard recorded under non-saturating conditions.

X-band EPR spectra were obtained on a Bruker EMX spectrometer equipped with an ER 4116 DM Dual Mode resonator operated in perpendicular mode at 10 K using an Oxford Instruments ESR900 helium flow cryostat. Bruker Win-EPR software (ver. 3.0) was used for data acquisition. Spectra were simulated using the EasySpin (Stoll and Schweiger, 2006 (link)) simulation toolbox (release 5.2.28) with Matlab 2020b.