Determination of the 14N quadrupole coupling constant of nitroxide spin probes by W-band ELDOR-detected NMR

Study of electron spectral diffusion process under DNP conditions by ELDOR spectroscopy focusing on the <sup>14</sup>N Solid Effect

“…S1 in ESI). The g-values obtained differ from those reported by Florent et al (Florent et al, 2011) ( 3)At the start of all our simulations, the Hamiltonian for each set of ( , )  angles is represented in matrix form, in the twelve product states of the basis sets in the laboratory…”

“…To analyze these ELDOR spectra we established a theoretical framework that accounts for all 14 N-SE and 1 H-SE depletions observed in these spectra. For this low concentration, the ELDOR spectrum is identical to the ELDOR detected NMR (EDNMR) spectrum of nitroxide, which has already been studied and simulated in the past (Cox et al, 2017;Florent et al, 2011;Kaminker et al, 2014;Nalepa et al, 2014Nalepa et al, , 2018). Yet, there is one major difference: Under EDNMR conditions, where resolution is of prime interest, the MW irradiation period is short, in the microsecond range, and therefore relaxation processes play a limited role during that irradiation.…”

ELDOR-detected NMR beyond hyperfine couplings: a case study with Cu(ii)-porphyrin dimers

“…50 The approach used here to determine the quadrupole coupling is analogous to that employed for nitroxides at W-band, where the coupling can be determined by analyzing a series of spectra at the high-field edge of the EPR spectrum. 37 An energy level diagram for our particular situation is shown in the ESI † (see Section S.7.1). Note that the spectra are asymmetric with respect to zero offset because the detection is selective with respect to the copper hyperfine components.…”

“…Additionally, we determine the copper quadrupole coupling in a similar way as previously shown for nitroxides. 37 A recently proposed fast simulation algorithm 4 quantitatively reproduces the experiment in spectral regions where only copper signals contribute to the spectrum. In the case of a relatively strong exchange coupling in f-CuP2…”

Direct Spectroscopic Detection of ATP Turnover Reveals Mechanistic Divergence of ABC Exporters

“…Toward this end, we substituted the EPR-silent essential metal co-factor Mg 2+ , which is coordinated to nucleotides at the NBSs, with the paramagnetic Mn 2+ ion ( S = 5/2) and followed the coupling to the 31 P nuclei ( I = 1/2) of the coordinated nucleotide phosphate and the 14 N nuclei contributed by the bound nucleotide and by transporters’ residues, through a series of freeze-quench experiments. While ENDOR is a well-established technique and is particularly useful for characterizing the coordination sphere of Mn 2+ , EDNMR has been gaining attention only during the last decade as a result of the increase use of high field EPR spectrometers (Banerjee et al, 2011; Bruch et al, 2015; Cox et al, 2013; Cox et al, 2015; Fittipaldi et al, 2008; Florent et al, 2011; Kaminker et al, 2010; Kaminker et al, 2014; Klein et al, 2012; Kulik et al, 2005; Mino and Ono, 2003; Nalepa et al, 2014; Potapov et al, 2012; Rapatskiy et al, 2012; Un, 2013). Here we show that the intensity of the EDNMR signal can be utilized to follow the evolution of the ATP turnover reaction.…”