Issue 20, 2022

Milliwatt three- and four-pulse double electron electron resonance for protein structure determination

Abstract

Electron paramagnetic resonance (EPR) experiments for protein structure determination using double electron–electron resonance (DEER) spectroscopy rely on high-power microwave amplifiers (>300 W) to create the short pulse lengths needed to excite a sizable portion of the spectrum. The recently introduced self-resonant microhelix combines a high B1 conversion efficiency with an intrinsically large bandwidth (low Q-value) and a high absolute sensitivity. We report dead times in 3-pulse DEER experiments as low as 14 ± 2 ns achieved using less than 1 W of power at X-band (nominally 9.5 GHz) for experiments on a molecular ruler and a T4 lysozyme sample for concentrations down to 100 μM. These low-power experiments were performed using an active volume 120 times smaller than that of a standard pulse EPR resonator, while only a 11-fold decrease in the signal-to-noise ratio was observed. Small build sizes, as realized with the microhelix, give access to volume-limited samples, while shorter dead times allow the investigation of fast relaxing spin species. With the significantly reduced dead times, the 3-pulse DEER experiment can be revisited. Here, we show experimentally that 3-pulse DEER offers superior sensitivity over 4-pulse DEER. We assert that the microhelix paves the road for low-cost benchtop X-band pulse EPR spectrometers by eliminating the need for high-power amplifiers, accelerating the adoption of pulse EPR to a broader community.

Graphical abstract: Milliwatt three- and four-pulse double electron electron resonance for protein structure determination

Supplementary files

Article information

Article type
Paper
Submitted
21 Dec 2021
Accepted
09 May 2022
First published
09 May 2022
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2022,24, 12528-12540

Milliwatt three- and four-pulse double electron electron resonance for protein structure determination

M. Teucher, J. W. Sidabras and A. Schnegg, Phys. Chem. Chem. Phys., 2022, 24, 12528 DOI: 10.1039/D1CP05508A

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