ENDOR studies of flavins and flavoproteins

Kurreck, H.; Bretz, Norbert; Helle, N.; Henzel, N.; Weilbacher, E.

doi:10.1039/f19888403293

Cited by 18 publications

(17 citation statements)

References 3 publications

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“…The hfc of this methyl group reacts sensitively to changes in the electron spin density on the outer xylene ring and to micropolarity changes of the protein surroundings [33]. Moreover, as has been shown in a number of experimental [18, 19] and theoretical [38] studies on flavin radicals, the H(8 α ) hfcs of anion radicals, are in general, significantly larger when compared with those in neutral radicals. This is because deprotonation of N(5) results in a significant redistribution of the unpaired electron spin density from the pyrazine and pyrimidine rings of the isoalloxazine moiety towards the less polar xylene ring.…”

Section: Discussionmentioning

confidence: 99%

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The Electronic State of Flavoproteins: Investigations with Proton Electron–Nuclear Double Resonance

et al. 2009

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Electron–nuclear double resonance (ENDOR) spectroscopy provides useful information on hyperfine interactions between nuclear magnetic moments and the magnetic moment of an unpaired electron spin. Because the hyperfine coupling constant reacts quite sensitively to polarity changes in the direct vicinity of the nucleus under consideration, ENDOR spectroscopy can be favorably used for the detection of subtle protein–cofactor interactions. A number of pulsed ENDOR studies on flavoproteins have been published during the past few years; most of them were designed to characterize the flavin cofactor by means of its protonation state, or to detect individual protein–cofactor interactions. The aim of this study is to compare the pulsed ENDOR spectra from different flavoproteins in terms of variations of characteristic proton hyperfine values. The general concept is to observe limits of possible influences on the cofactor's electronic state by surrounding amino acids. Furthermore, we compare ENDOR data obtained from in vivo experiments with in vitro data to emphasize the potential of the method for gaining molecular information in complex media.

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Section: Discussionmentioning

confidence: 99%

“…Here, we restrict ourselves on ENDOR data from chemically unmodified flavins as only very few data from chemically modified flavins is available up to now (see, e.g., Refs. [17–19]).…”

Section: Introductionmentioning

confidence: 99%

The Electronic State of Flavoproteins: Investigations with Proton Electron–Nuclear Double Resonance

et al. 2009

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“…Guided by DFT calculations, the three principal components of the 2 H(6) hf tensor including their signs and the strength of the nqc (see also below) could be assigned with high accuracy, as the spectral overlap with resonances from other deuterons is negligible in the [6,8α- 2 H 4 ]LOV* sample. Previous hyperfine studies dealt with the couplings of H(6); X-band proton Davies-ENDOR experiments were used in most of them (see, e.g., refs , , , and − ). Typically, only one component of the H(6) hf tensor was reported and attributed to the A iso value.…”

Section: Discussionmentioning

confidence: 99%

Coupled Methyl Group Rotation in FMN Radicals Revealed by Selective Deuterium Labeling

et al. 2020

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“…17 O ENDOR has been recorded in beef heart aconetase [76] and in horseradish peroxidase [77]. 33 S ENDOR has been recorded for MoFe protein [69] and 19 F ENDOR has been detected for flavin radicals [80] in flavins [81] and flavo-proteins [81] in different protonation sites. The [4Fe-4S] cluster was studied using 17 O ENDOR in beef heart aconetase.…”

Section: Free Radicals In Biological Systemsmentioning

confidence: 99%

“…In horseradish peroxidase, the O atom comes from the oxidant, the Fe portion of the system is an oxy-ferryl (Fe IV = O) moiety. The influence of different substituents on the spin distribution within the isocelloxazine ring was deduced [81]. 95,97 Mo ENDOR was recorded for MoFe proteins [72], and 95 Mo protein [79], where 95 Mo hyperfine and quadrupole coupling constants indicated that a single Mo atom was integrated into the MoFe spin system.…”

Section: Free Radicals In Biological Systemsmentioning

confidence: 99%

Endor Spectroscopy

Kispert

Piekara-Sady

Handbook of Applied Solid State Spectroscopy

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To understand what electron nuclear double resonance (ENDOR) transitions are, let us consider the energy levels of a system containing one unpaired electron (S = ½) and one nuclear spin (I = ½), as in a hydrogen atom. Since the electron spin and nuclear spin can each be oriented with or against the external magnetic field, there are four possible energy levels as shown in Figure 4.1. The two electron spin eigenfunctions are denoted by e and e , whereas the two nuclear spin wavefunctions are denoted n and n . In the presence of a large external applied field, the selection rule in electron paramagnetic resonance (EPR) is that the electron flips (changes directions) but the nuclear spin does not flip in an EPR transition. Thus, in Figure 4.1, an EPR transition will occur between energy levels 1 and 4 and a second EPR transitions will occur between energy levels 2 and 3. The intensity of the transition between energy levels 1 and 4 will depend on the population differences of these two energy levels. If one then applies a nuclear frequency to the system, which corresponds to either the energy difference between levels 4 and 3 or the difference between lines 2 and 1, one will induce nuclear spin flip that will change the populations in energy levels 4 and 1, respectively. This changes the intensity of the observed EPR signal. This change in intensity is referred to as the ENDOR response. Figure 4.1 Energy diagram for S = 1/2 and I = 1/2.

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ENDOR studies of flavins and flavoproteins

Cited by 18 publications

References 3 publications

The Electronic State of Flavoproteins: Investigations with Proton Electron–Nuclear Double Resonance

The Electronic State of Flavoproteins: Investigations with Proton Electron–Nuclear Double Resonance

Coupled Methyl Group Rotation in FMN Radicals Revealed by Selective Deuterium Labeling

Endor Spectroscopy

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