Intensity of Cross-Peaks in Hyscore Spectra of S = 1/2, I = 1/2 Spin Systems

Hydrogen Bonds Involved in Binding the Qi-site Semiquinone in the bc1 Complex, Identified through Deuterium Exchange Using Pulsed EPR

“…͉Tϩ2a͉ Ͼ Ͼ 4 I , whereas the peaks in the (ϩ,ϩ) quadrant appear predominantly for ͉Tϩ2a͉Ͻ Ͻ 4 I (where a is the isotropic hyperfine coupling, T is the perpendicular component of the axial anisotropic hyperfine tensor, and I is the nuclear Zeeman frequency). Peaks may appear in both quadrants simultaneously if the hyperfine and Zeeman couplings are comparable (16). In the present work, the cross-peaks from protons were located in (ϩ,ϩ) quadrant only.…”

“…It has been shown that for strongly non-axial hyperfine tensors, up to three separate ridges (even observed in both quadrants) may appear in the HYSCORE spectrum (16). The regression lines of such ridges must form a triangle, with apices on the ͉ ␣ ϩ ␤ ͉ ϭ 2 I curve; however, the regression lines in Fig.…”

Extreme deuterium enrichment of organic radicals in the Orgueil meteorite: Revisiting the interstellar interpretation?

“…The presence of weak maxima along the ridge, indicates that several types of C-H bonds participate to the hydrogen pattern. In principle such intensity modulation could be due to ''blind spot effect" with a single well-defined H atom (Dikanov et al, 2000). However the fact that these structures are still observed at s = 128 ns (but with a lower intensity of hydrogen ridge) and at s = 200 ns (but with less pronounced maxima) shows that they can be attributed to modulation peaks of different H. Therefore, the molecular localization of deuterium and hydrogen in radicals appears quite different: (1) Hydrogen is distributed among all the possible sites of small polycyclic moieties (p-radicals) (Ikoma et al, 1998;Gerson and Huber, 2003) as shown by the electron-spin density q p 6 0.12 on carbon measured from the maximum hf interaction | H A max | = 12.3 ± 0.2 MHz (see Appendix A for details), while (2) Deuterium is much less distributed, and more localized in a specific C-D bond.…”

Spin distribution of the H-cluster in the Hox–CO state of the [FeFe] hydrogenase from Desulfovibrio desulfuricans: HYSCORE and ENDOR study of 14N and 13C nuclear interactions

“…Unfortunately, a complete analysis is not possible using this method since at the lower magnetic field (around g 1 ) these signals are not observable in the HYSCORE spectra (data not shown here). It is well known that signals from nuclei with hyperfine couplings close to exact cancellation (A & 2m n ) are most prominent in ESEEM spectra, while signals from strongly coupled nuclei vanish with increasing hyperfine coupling constant [61]. Apparently, at this field position the NMR frequencies of the 13 C signals are too large to be detected using this method; therefore, additional Q-band ENDOR measurements were performed to extract all the parameters of this 13 C hyperfine coupling.…”