Structure of the Tyrosyl Biradical in Mouse R2 Ribonucleotide Reductase from High‐Field PELDOR

Abstract

Paramagnetic centers rigidly embedded in proteins serve as a probe in structural studies of macromolecular complexes. Pulse EPR at high frequencies allows the determination of not only the distance but also the relative orientation of these centers (see tyrosyl radicals; C gray, O red, N blue). The method has considerable potential for studying the assembly of protein complexes.

HYSCORE and DEER with an upgraded 95GHz pulse EPR spectrometer

“…However, in the case of orientation selection and correlated orientations of the two radicals the modulation depth k depends on the orientation selected by the observer and pump pulses and by the relative orientation of the g-tensors [9,10,12]. DEER measurements were carried out with two pulse settings.…”

“…In the last decade numerous applications of high field CW EPR and ENDOR have been reported and the virtues of measurements at a high field have been well demonstrated and established [1][2][3][4][5][6]. Recently, it has also been demonstrated that distance measurements between paramagnetic centers by pulsed DEER techniques can also be performed at high fields [9][10][11][12]. Distance measurements have become very popular in the last few years and are carried out usually at X-band frequencies [7,8].…”

“…Distance measurements have become very popular in the last few years and are carried out usually at X-band frequencies [7,8]. The high field measurements offer additional information such as the relative orientations of the g-tensors of the two coupled paramagnetic centers [10]. Among the above mentioned high resolution EPR techniques, the absence of applications of electron-spin echo modulation (ESEEM) spectroscopy is conspicuous.…”

Geometric model-based fitting algorithm for orientation-selective PELDOR data

“…The second case corresponds to those time traces for which only certain orientations of the spin-spin vector r relative to the external magnetic field B 0 were excited. Examples for such a case are the tyrosine radicals in the ribonucleotide reductase dimer [9,10], the rigid spin label Ç in oligonucleotides [11,12], spin labels restricted in their rotational freedom by the protein environment [13,14] or transition metal * Corresponding author. Email: schiemann@pc.uni-bonn.de ions/clusters [15][16][17][18][19][20][21][22].…”

A dual-mode microwave resonator for double electron–electron spin resonance spectroscopy at W-band microwave frequencies

“…Among the most important is the pulsed electron-electron double resonance technique (PELDOR, also called DEER), which allows measurement of long range distances (2-8 nm) between two paramagnetic species in macromolecules [1][2][3][4][5][6]. At high magnetic fields, PELDOR experiments can also deliver information about the relative orientations of paramagnetic species [7][8][9][10][11][12][13]. This is a valuable information to study conformational changes of macromolecules or assemblies of protein complexes in which paramagnetic centers are rigidly embedded.…”