# Pulsed Q-band Electron Paramagnetic Resonance Spectrometer for Structural Biology Applications

> **NIH NIH S10** · NORTHWESTERN UNIVERSITY · 2024 · $1,899,161

## Abstract

PROJECT SUMMARY/ABSTRACT
The instrument to be acquired is a state-of-the-art Pulsed Q-band Electron Paramagnetic Resonance (EPR)
spectrometer and will be a multi-user shared instrument at the Integrated Molecular Structure Education and
Research Center (IMSERC) user facility, accessible to all Northwestern University (NU) users and users of the
greater Chicago area. The objective is to support the major user needs, from structural biology of folded proteins,
intrinsically disordered proteins, to biomolecular assemblies developed as novel therapeutic agents. The
spectrometer configuration is optimized for distance measurements between spin labels, transition metal centers
and nuclear spins, and their combinations in both the strong and weak coupling limit and between species with
differences in EPR frequency exceeding the resonator bandwidth. These objectives will be achieved with a pulsed
Q-band EPR spectrometer equipped with arbitrary waveform generation (AWG), a high-power (300 Watt)
microwave amplifier, a QT-II resonator that can be strongly overcoupled for pulsed dipolar EPR spectroscopy
(PDS), a Electron Nuclear Double Resonance (ENDOR) resonator and a cryogen-free cryostat that accommodates
both resonators to operate at 5-300 K, on demand. The Q-band frequency, the bandwidth and B1 conversion
efficiency of the resonators combined with the high-power microwave and AWG is an ideal hardware
configuration for Double Electron Electron Resonance (DEER). It is additionally suitable for experiments relying
on single frequency broad-band excitation, such as Relaxation Induced Dipolar Modulation Experiment (RIDME)
that is suitable for distance measurements between a spin label and a fast-relaxing transition metal. This will be
the first shared pulsed Q-band system established in a user facility at NU. The expert labs of Wasielewski and
Hoffman have specialized EPR setups configured for quantum information science and metallobiology but are
not equipped with a pulsed Q-band systems that offer high microwave power and continuous cryogen-free
operation, all of which are key to user operation. The Han lab is equipped with a similar instrument, without
ENDOR, but the usage of this lab’s Q-band instrument reaches 100% AUT by the Han lab users alone. When
combined with the total user need for pulsed Q-band EPR proposed for the requested instrument, AUT easily
reaches 200%. Automated sharing of the Han lab resource will keep both instruments fully occupied. This is
reflective of one major limitation of DEER today: long experimental times of 12 to 24 hours for one single
experiment is routine, while the total major user needs readily exceeds 7 to 14 experiments per week. The Han
lab is collaborating with experts to develop and test innovative methods aimed at shortening the experimental
time by implementing non-uniform sampling, by signal averaging with pre-processed single scan data and by
applying a total analysis of signal and background in one through wav...

## Key facts

- **NIH application ID:** 10869435
- **Project number:** 1S10OD036453-01
- **Recipient organization:** NORTHWESTERN UNIVERSITY
- **Principal Investigator:** Songi Han
- **Activity code:** S10 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $1,899,161
- **Award type:** 1
- **Project period:** 2024-09-01 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10869435

## Citation

> US National Institutes of Health, RePORTER application 10869435, Pulsed Q-band Electron Paramagnetic Resonance Spectrometer for Structural Biology Applications (1S10OD036453-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10869435. Licensed CC0.

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