An Implicit TRIPLE Effect in Mims Pulsed ENDOR:  A Sensitive New Technique for Determining Signs of Hyperfine Couplings

Doan, Peter E.; Nelson, Mark J.; Hu, Jin; Hoffman, Brian M.

doi:10.1021/ja960611k

Cited by 59 publications

(68 citation statements)

References 10 publications

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“…In addition, when going to higher excitation frequencies strong-level mixing is usually reduced, consequently, the ENDOR effect is enhanced and the ESEEM effect is reduced, i.e. the impacts of cross-suppression and implicit triple [10,11] are decreased. Compared to ENDOR at even higher frequencies, Q-band pulse ENDOR has substantially better concentration sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications

Tschaggelar

Kasumaj

Santangelo

et al. 2009

Journal of Magnetic Resonance

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Section: Introductionmentioning

confidence: 99%

Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications

Tschaggelar

Kasumaj

Santangelo

et al. 2009

Journal of Magnetic Resonance

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“…The structure of the iron center in the active form has been studied by various spectroscopies including ESR (3), resonance Raman (13), extended x-ray absorption fine structure (13) and electron nuclear double resonance (14), and the ligand-donor set of N 3 OS 2 has been proposed (14), which is supported by model complexes of the iron center (15)(16)(17). Recently, the metal site structure has been studied in detail by means of electron nuclear double resonance (18), resonance Raman (19), and x-ray absorption (20) spectroscopies. It was demonstrated that the coordination sphere of the metal site consisted of two cis-coordinated sulfhydryl ligands, three His imidazole ligands, and an exchangeable solvent ligand, probably an hydroxo group.…”

mentioning

confidence: 99%

Structure of the Photoreactive Iron Center of the Nitrile Hydratase from Rhodococcus sp. N-771

Tsujimura

Dohmae

Odaka

et al. 1997

Journal of Biological Chemistry

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Nitrile hydratase (NHase) from Rhodococcus sp. N-771 is a photoreactive enzyme that is inactivated by nitrosylation of the non-heme iron center and activated by photodissociation of nitric oxide (NO). To obtain structural information on the iron center, we isolated peptide complexes containing the iron center by proteolysis. When the tryptic digest of the ␣ subunit isolated from the inactive form was analyzed by reversed-phase high performance liquid chromatography, the absorbance characteristic of the nitrosylated iron center was observed in the peptide fragment, Asn 105 -Val-Ile-Val-CysSer-Leu-Cys-Ser-Cys-Thr-Ala-Trp-Pro-Ile-Leu-Gly-LeuPro-Pro-Thr-Trp-Tyr-Lys 128 . The peptide contained 0.79 mol of iron/mol of molecule as well as endogenous NO. Subsequently, by digesting the peptide with thermolysin, carboxypeptidase Y, and leucine aminopeptidase M, we found that the minimum peptide segment required for the nitrosylated iron center is the 11 amino acid residues from ␣Ile 107 to ␣Trp 117 . Furthermore, by using mass spectrometry, protein sequence, and amino acid composition analyses, we have shown that the 112th Cys residue of the ␣ subunit is post-translationally oxidized to a cysteine-sulfinic acid (Cys-SO 2 H) in the NHase. These results indicate that the NHase from Rhodococcus sp. N-771 has a novel non-heme iron enzyme containing a cysteine-sulfinic acid in the iron center. Possible ligand residues of the iron center are discussed.Nitrile hydratase (NHase; EC 4.2.1.84) 1 is a bacterial metalloenzyme catalyzing the hydration of nitriles to corresponding amides (1, 2). NHase consists of two kinds of subunits (␣ and ␤ with the molecular mass values of 23 kDa) and contains non-heme iron (3) or non-corrinoid cobalt (4) atoms. The NHase from Rhodococcus sp. N-771, which is a ␣␤ heterodimer containing a non-heme iron, is inactivated by aerobic incubation in the dark for a half-day (dark-inactivation), whereas the enzyme purified from the dark-inactivated cells is immediately converted to the active form by light irradiation (photoactivation) (5, 6). Recently, it has been revealed that dark-inactivation and photoactivation are controlled by association and photodissociation of nitric oxide (NO) with the non-heme iron center (7-9). Similar photosensitivity is observed in the NHases from Rhodococcus sp. N-774 (10) and R312.2 These NHases seem to be identical to the one from Rhodococcus sp. N-771 because of the same nucleotide sequences (11, 12). 3The iron-containing NHase is the first enzyme with a mononuclear low-spin non-heme iron(III) which is thought to be involved in the catalysis (3). The structure of the iron center in the active form has been studied by various spectroscopies including ESR (3), resonance Raman (13), extended x-ray absorption fine structure (13) and electron nuclear double resonance (14), and the ligand-donor set of N 3 OS 2 has been proposed (14), which is supported by model complexes of the iron center (15-17). Recently, the metal site structure has been studied in detail by means of electro...

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“…The first involves having an accessible Fe coordination site as in the mononuclear Fe centers of nitrile hydratase 25, 26 and SOR, 31, 73 and the [4Fe-4S] clusters at the active sites of hydratases/dehydratases 27,28 and radical-S-adenosylmethionine (SAM) enzymes.…”

Section: [2fe-2s] [3fe-4s] and [4fe-4s] Clustersmentioning

confidence: 99%

Iron–Sulfur Proteins

Johnson

Smith

2005

Encyclopedia of Inorganic Chemistry

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Iron–sulfur proteins contain iron coordinated by at least one sulfur ligand and include proteins with mononuclear Fe centers with partial or complete cysteinyl sulfur ligation as well as proteins containing clusters of iron and inorganic sulfide. This review summarizes the structural, electronic, and redox properties of protein‐bound mononuclear FeS centers and FeS clusters containing [2Fe2S], [3Fe4S], and [4Fe4S] cores. In addition to the ubiquitous role in mediating biological electron transport, the roles of FeS centers have proliferated to include coupling of electron and proton transfer, substrate binding and activation, determining protein structure, regulation of gene expression and enzymatic activity, disulfide reduction, and iron, electron, or cluster storage. The diverse roles of FeS clusters are illustrated by discussion of specific systems: the mitochondrial and photosynthetic electron transport chains and a wide range of soluble redox enzymes and proteins; the active sites of nitrile hydratase, aconitase‐type (de)hydratases, superoxide reductase (SOR), radical‐SAM (S‐adenosylmethionine) enzymes, NiFe‐ and Fe‐hydrogenase, sulfite and nitrite reductase, nitrogenase, CO dehydrogenase, and acetyl‐CoA synthase; the structural FeS centers in DNA repair enzymes; the regulatory roles of FeS centers in the SoxR, fumarate–nitrate reduction (FNR), IscR/SufR, and iron‐regulatory protein (IRP) proteins and in selected enzymes; the two classes of FeS cluster containing disulfide reductases typified by ferredoxin–thioredoxin reductase (FTR) and heterodisulfide reductase (HDR); and the role of 8Fe ferredoxins and polyferredoxins in iron, electron, or cluster storage.

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An Implicit TRIPLE Effect in Mims Pulsed ENDOR: A Sensitive New Technique for Determining Signs of Hyperfine Couplings

Cited by 59 publications

References 10 publications

Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications

Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications

Structure of the Photoreactive Iron Center of the Nitrile Hydratase from Rhodococcus sp. N-771

Iron–Sulfur Proteins

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