TY - JOUR
T1 - Robustness and sensitivity of Gd(III)-Gd(III) double electron electron resonance (DEER) measurements
T2 - comparative study of high-frequency EPR spectrometer designs and spin label variants
AU - Mocanu, Elena Mihaela
AU - Ben-Ishay, Yasmin
AU - Topping, Lydia
AU - Fisher, Stuart Ronan
AU - Hunter, Robert Iain
AU - Su, Xun-Cheng
AU - Butler, Stephen
AU - Smith, Graham Murray
AU - Goldfarb, Daniella
AU - Lovett, Janet Eleanor
N1 - Funding: This work was supported financially by the Bluston Making Connections (UK-WIS) scheme, The Royal Society (International Exchanges) and the Carnegie Trust. The Q-band spectrometer high power Q-band with cryogen-free upgrade was provided by the Wellcome Trust (099149/Z/12/Z) and the BBSRC (BB/T017740/1) respectively. The authors thank EPSRC (EP/N509759/1) and the School of Physics and Astronomy, St Andrews for studentships for SRF and EMM respectively.
PY - 2025/1/3
Y1 - 2025/1/3
N2 - In this paper we explore the robustness and sensitivity of Gd(III)-Gd(III) double electron-electron resonance (DEER) distance measurements in proteins for different spectrometer designs and a three spin labels. To do this a protein was labelled at the same two positions with Gd(III) spin labels and measurements were performed on two home-built high-frequency (W-band, ~95 GHz) EPR spectrometers with different design approaches, and a commercial Q-band spectrometer. The first W-band measurement approach uses a conventional, narrow band single mode cavity, while the second approach uses a broad band non-resonant induction mode sample holder. Both systems incorporate advanced arbitrary waveform generators (AWGs) that give flexibility over excitation bandwidth. We use three DOTA-like Gd(III) spin labels, Gd.C12, Gd.DO3A and the new Gd.L1, conjugated to the model protein calmodulin. We compare measurements taken by including or excluding the excitation of the Gd(III) central transition. The advantages and disadvantages of the EPR spectrometers for the measurement of Gd(III)-Gd(III) DEER are discussed in terms of the robustness of the resulting distance distribution width, absolute and concentration sensitivity, sample handling, ease of use, and flexibility of measurement.
AB - In this paper we explore the robustness and sensitivity of Gd(III)-Gd(III) double electron-electron resonance (DEER) distance measurements in proteins for different spectrometer designs and a three spin labels. To do this a protein was labelled at the same two positions with Gd(III) spin labels and measurements were performed on two home-built high-frequency (W-band, ~95 GHz) EPR spectrometers with different design approaches, and a commercial Q-band spectrometer. The first W-band measurement approach uses a conventional, narrow band single mode cavity, while the second approach uses a broad band non-resonant induction mode sample holder. Both systems incorporate advanced arbitrary waveform generators (AWGs) that give flexibility over excitation bandwidth. We use three DOTA-like Gd(III) spin labels, Gd.C12, Gd.DO3A and the new Gd.L1, conjugated to the model protein calmodulin. We compare measurements taken by including or excluding the excitation of the Gd(III) central transition. The advantages and disadvantages of the EPR spectrometers for the measurement of Gd(III)-Gd(III) DEER are discussed in terms of the robustness of the resulting distance distribution width, absolute and concentration sensitivity, sample handling, ease of use, and flexibility of measurement.
U2 - 10.1007/s00723-024-01741-0
DO - 10.1007/s00723-024-01741-0
M3 - Article
SN - 0937-9347
VL - Early View
JO - Applied Magnetic Resonance
JF - Applied Magnetic Resonance
ER -