Facilities

The equipment and resources available at the National Biomedical EPR Center are detailed below.

EPR Spectrometers

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   Bruker ELEXSYS EPR Spectrometer Systems (2)

Special Features

Super X bridge, high dynamic range (90 dB), X-band, 10-inch magnet, Super Hi-Q resonator, ER 4103TM cylindrical resonator, ER 4116DM dual-mode TE102/TE012 resonator ER 4117D-R dielectric resonator, ER 4117D-M dielectric mixing resonator, ER 4119HS-WI high-sensitivity optical resonator, and liquid nitrogen cryostat. One of the ELEXSYS spectrometers is equipped with field frequency lock, helium cryostat, Bruker DICE ENDOR with ENH01252 cavity, A300 RF power amplifier (0.3 to 35 MHz), and 3100L RF power amplifier (250 kHz to 105 MHz). Bruker E-600 series W-band CW-EPR (including W-band cylindrical resonator, W-band bridge, superconducting magnet, room temperature sweep coils, and cryostat).

  Bruker ELEXSYS 580 Pulsed Spectrometer

Special Features

Pulse X-band spectrometer and Q-band with DEER, DQC, and ENDOR capabilities at cryogenic temperatures.

Applications

To measure long-range distances between paramagnetic probes and/or coupled nuclei within biomedically-relevant proteins and peptides.

  Bruker EMX Spectrometer

Special Features

Standard high-quality X-band research instrument.

Applications

Photoexcited paramagnetic states; spin-label studies; spin-label studies of cellular membrane fluidity and oxygen uptake.

  Time-Domain ESR Spectrometer at 9 GHz with 9-inch Magnet

Special Features

Saturation recovery capability to 0.1 microsecond; very high speed data acquisition system.

Applications

Measurement of T1 of spin labels; measurement of transient response of spin systems to various excitations.

  Low-Frequency EPR Spectrometer Station

Special Features

CW and NARS spectroscopy at 0.5 to 1 GHz, 1 to 2 GHz, 2 to 4 GHz, and 4 to 8 GHz at temperatures down to 15 to 20 K.

Applications

Transition metal EPR studies, protein distance measurements.

  Varian E-9 EPR Multifrequency Spectrometer

Special Features

0.5 to 1 GHz bridge; L-band 1-2 GHz bridge; S-band 2-4 GHz bridge; C-band 4-8 GHz bridge; K-band 18 GHz bridge; Q-band 35 GHz bridge; various loop-gap resonators; liquid helium cooling at all of the above frequencies (down to 15-20 K).

Applications

Transition metal EPR; forbidden transitions; in vivo studies on mice; study of very small samples at 35 GHz.

  Varian E-109 Century Series EPR Spectrometers

Special Features

Field-frequency locks; photomodulation from dc to 5 kHz; saturation transfer spectroscopy; excellent sensitivity; loop-gap resonators.

Applications

EPR of free radicals in solution; EPR of metal complexes in frozen solution; photoexcited paramagnetic states; spin-label studies; spin-label studies of cellular membrane fluidity and oxygen uptake.

  Modified Varian E-110 Q-Band (35 GHz) Spectrometer Station

Special Features

High sensitivity, low phase noise Q-band microwave bridge on a varian-based console and magnet system.

  Multiquantum Q-Band Spectrometer with 10-inch Bruker Magnet

Special Features

Multiquantum and saturation recovery spectroscopy at 35 GHz.

Applications

Resolution of multiple spectral components that arise from conformational equilibria.

  W-Band Spectrometer

Special Features

92.5–95.5 GHz CW and saturation recovery spectrometer. Can measure T1s to 200 nS.

Applications

Specialized for use with room-temperature liquid-phase aqueous samples.

Resources

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  Electronic Equipment
  • Agilent E5505A Phase Noise Measurement System
  • Agilent N5242A PNA-X Network Analyzer (Heads to 240 GHz)
  • Agilent E8363C PNA Network Analyzer (50 MHZ to 40 GHz)
  • Agilent N9030A PXA Signal Analyzer (3 Hz to 44 GHz)
  • Agilent Spectrum Analyzers to 100 GHz
  • Agilent Microwave Power Meters to 100 GHz
  • Frequency Counters to 40 GHz
  • Agilent DSO9404 Digitizing Oscilloscope to 40 GSPS
  • Analog Oscilloscopes to 400 MHz
  • Pulse, delay, and signal generators
  Software

Software resources include the following:

  • Agilent Advance Design System (ADS) is a PC-based microwave circuit design, simulation, and layout system
     
  • Ansys High-Frequency Structure Simulator (HFSS) running on a Dell computer with dual 12-core 2.3 GHz Xeon processors with 512 GB of memory and nVidia CUDA enabled graphics processors, permitting objective (rather than intuitive) design of loop-gap resonator coils and cavities, and is useful for modeling RF field distributions
     
  • Ansys Maxwell 3D, a field simulator that uses finite-element analysis to solve electromagnetic problems; it is run on the same computer as Ansoft HFSS
     
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