Er 4112 hv helium flow cryostat

The CW EPR spectra were measured on an ELEXSYS E540 X-band spectrometer (Bruker-Biospin, Billerica, MA) with an ER 4102 ST resonator using 100 kHz magnetic field modulation. Spectra were measured at 77 K in a liquid-nitrogen quartz insertion dewar and at lower temperatures with a Bruker ER 4112 HV helium flow cryostat. Care was taken to avoid microwave power saturation or modulation broadening in the CW EPR spectra that are reported or analyzed.

CW EPR spectra were measured on a Bruker ELEXYS E540 X-band spectrometer with an ER 4102 ST resonator (Bruker-Biospin, Billerica, MA). CW spectra were measured at a nominal microwave frequency of 9.45 GHz. Spectra were recorded at 77 K using a liquid-nitrogen quartz insertion Dewar or at 15 K using a Bruker ER 4112 HV helium flow cryostat.
HYSCORE measurements were made at 10–15 K with a nominal microwave frequency of 9.76 GHz using an ELEXSYS E680 EPR spectrometer (Bruker-Biospin, Billerica, MA) equipped with a Bruker Flexline ER 4118 CF cryostat and an ER 4118X-MD4 ENDOR resonator. HYSCORE measurements used a four pulse sequence, π/2−τ−π/2−t1−π−t2−π/2−τ−echo repeated at a rate of 2 kHz, where π/2 and π represent pulses 16 and 32 ns long, respectively, and t1, t2, and τ are delays between the pulses. The times t1 and t2 are varied independently to create the two dimensions of the HYSCORE spectrum. The delay time τ was set to 240 ns for all measurements except CYP2C9d with no drug added at 296.5 mT, which had a τ value of 288 ns to give a slightly more intense signal.