Pulsed-Electron Paramagnetic Resonance Spectrometer

Pulsed-EPR experiments, including electron spin echo-detected EPR (ESE-EPR), electron spin echo envelope modulation (ESEEM), electron spin echo electron-nuclear double resonance (ESE-ENDOR), Fourier-transform EPR (FT-EPR), and inversion and saturation recovery, are performed on a home designed and constructed pulsed-EPR spectrometer. A guiding principle in the design of the spectrometer was flexibility, both in terms of hardware and software. These features allow the immediate implementation of current developments in the rapidly progressing field of pulsed-EPR spectroscopy, and allow us to tailor the experiments as necessary for different biological samples.
The pulsed-EPR spectrometer operates continuously over X-band (8.2-12.4 GHz) and Ku-band (12.4-18.0 GHz) microwave frequencies. Broadband folded half wave resonators and loop gap resonators, and a modified Varian X-band cavity (TE) resonator are used to achieve different microwave frequencies and optimize different experiments. The detection bandwidth is ≤500 MHz and the pulse timing resolution is ≥1.6 ns. Sample temperatures from <2 K to 295 K are maintained by a Janis cryostat. ESE experiments are typically performed at 6 K. All operations are controlled via GPIB/IEEE-488 PC-device interfaces by using Matlab software.

Continuous-Wave Electron Paramagnetic Resonance Spectrometers

A Bruker E500 is used to perform continuous-wave EPR and ENDOR at X-band (~9.4 GHz) and Q-band (~31 GHz). Different cryostats allow EPR and ENDOR experiments to be performed from 4 K to room temperature.

Transient Optical Spectrophotometer

A home designed and constructed transient optical spectrometer is used to perform time-resolved absorbance (300-700 nm) spectroscopy. Light excitation of samples is provided by a pulsed-Nd-YAG laser, and the photo-induced absorbance changes are followed on time-scales of 100 ns to milliseconds by using a continuous-wave measuring beam with photomultiplier tube detection. Signals are digitized with a fast digital sampling oscilloscope. The spectrometer is computer controlled by using software coded in LabVIEW.

Continuous-wave Spectrophotometer

from shimadzu website

A commercial spectophotometer (Shimadzu UV1900i), which is interfaced with a PC, is used for routine spectrophotometry. This spectrophotometer has been outfitted with a home-built sample chamber and cryostat for low-temperature (100-250 K) optical studies of static samples or samples prepared by rapid mixing.