Compound ES of Cytochrome c Peroxidase Contains a Trp .pi.-Cation Radical: Characterization by Continuous Wave and Pulsed Q-Band External Nuclear Double Resonance Spectroscopy

Huyett, Jennifer E.; Doan, Peter E.; Gurbiel, Ryszard J.; Houseman, Andrew L. P.; Sivaraja, M.; Goodin, David B.; Hoffman, Brian M.

doi:10.1021/ja00140a021

Cited by 168 publications

(223 citation statements)

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“…Calculation of these values can be accomplished using Eqn. 4, which is derived from the expression (4) Use of this equation with "immmobilized" a β H values gives θ values of 55.7° and 64.3° for the tilt caused by the unequal steric interactions. An approximate value of 30° for the bulky constituent's oscillation around its equilibrium position can be obtained from the data of Stone and Maki by using the average of the experimental a β H s, 0.89 mT.…”

Section: β-Methylene Hydrogen Hyperfine Coupling Constantsmentioning

confidence: 99%

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l-Tryptophan Radical Cation Electron Spin Resonance Studies: Connecting Solution-Derived Hyperfine Coupling Constants with Protein Spectral Interpretations

et al. 2008

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Fast-flow electron spin resonance (ESR) spectroscopy has been used to detect a free radical formed from the reaction of L-tryptophan with Ce 4+ in an acidic aqueous environment. Computer simulations of the ESR spectra from L-tryptophan and several isotopically modified forms strongly support the conclusion that the L-tryptophan radical cation has been detected by ESR for the first time. The hyperfine coupling constants (HFCs) determined from the well-resolved isotropic ESR spectra support experimental and computational efforts to understand L-tryptophan's role in protein catalysis of oxidation-reduction processes. L-tryptophan HFCs facilitated the simulation of fast-flow ESR spectra of free radicals from two related compounds, tryptamine and 3-methylindole. Analysis of these three compounds' β-methylene hydrogen HFC data along with equivalent L-tyrosine data has led to a new computational method that can distinguish between these two amino acid free radicals in proteins without dependence on isotope labeling, electron nuclear double resonance or high-field ESR. This approach also produces geometric parameters (dihedral angles for the β-methylene hydrogens) which should facilitate protein site assignment of observed L-tryptophan radicals as has been done for L-tyrosine radicals.

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Section: β-Methylene Hydrogen Hyperfine Coupling Constantsmentioning

confidence: 99%

“…To exploit these differences, experimental β-methylene hyperfine couplings from protein ESR spectral simulations were used in Eqn. 4 Table 3 below and the much more extensive results for tyrosine are contained in Table 4 in supporting information.…”

Section: L-tryptophan and L-tyrosine Free Radicals In Proteinsmentioning

confidence: 99%

l-Tryptophan Radical Cation Electron Spin Resonance Studies: Connecting Solution-Derived Hyperfine Coupling Constants with Protein Spectral Interpretations

et al. 2008

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“…The presence of a tryptophan radical also cannot be ruled out on the basis of the 9.6-GHz EPR data, because tyrosine and tryptophan radicals can exhibit very similar EPR spectra at 9.6 GHz (34). It should also be noted that when amino acid radicals are even closer to the heme (3-4 Å), for example the tryptophan radical in cytochrome c peroxidase, they exhibit a completely different EPR spectrum, which is governed by a strong exchange interaction between the radical and the heme iron (35).…”

Section: Epr Spectroscopy At 96 Ghzmentioning

confidence: 99%

Tyrosine Radical Formation in the Reaction of Wild Type and Mutant Cytochrome P450cam with Peroxy Acids

Schünemann

Lendzian²,

Jung

et al. 2004

Journal of Biological Chemistry

108

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“…However, it includes the other types of information of Table 1, too, ranging from the location of a single electron (hole) and a single proton in a highvalent intermediate (18), a task for which ENDOR spectroscopy is perhaps uniquely suited, to information about dynamics (19), an area where ENDOR͞ESEEM spectroscopies might have been thought unsuitable. As a result of all this, in favorable cases these methods can definitively characterize elusive enzymic mechanisms, the ''highest'' goal of Table 1.…”

Section: Information Recoveredmentioning

confidence: 99%

Electron-nuclear double resonance spectroscopy (and electron spin-echo envelope modulation spectroscopy) in bioinorganic chemistry

Hoffman

2003

Proc. Natl. Acad. Sci. U.S.A.

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This perspective discusses the ways that advanced paramagnetic resonance techniques, namely electron-nuclear double resonance (ENDOR) and electron spin-echo envelope modulation (ESEEM) spectroscopies, can help us understand how metal ions function in biological systems.T he invitation to write this article explained, ''Perspective articles are intended to survey, from the author's distinctive perspective, some frontier aspects of the featured field and to highlight important recent developments and challenges.'' Within that definition, I shall discuss the ways that advanced paramagnetic resonance techniques, namely electron-nuclear double resonance (ENDOR) spectroscopy (1) and its junior partner electron spin-echo envelope modulation (ESEEM) spectroscopy (2), help us understand how metal ions function in biological systems and provide information in all of the critical categories listed in Table 1. In these early days of proteomics, where the primary sequence of all proteins in an organism are knowable in principle, and increasingly in fact, and where large-scale efforts are under way to determine the resting-state x-ray crystal structures of these proteins, this article is a representative response to the broader question: what roles do spectroscopies play? The answer, of course, is many, and important ones. BackgroundKey information about the composition, bonding, and structure of a paramagnetic metal center can be obtained by analysis of the electron-nuclear hyperfine and nuclear quadrupole couplings (3) of nuclei associated with endogenous and exogenous metal ligands, enzymebound substrates, inhibitors, and products, as well as the metal ions themselves. In principle, these couplings can be derived from splittings observable in a center's EPR spectrum. For most metallo-biomolecules, however, a variety of factors make these interactions unresolvable for most (or any) nuclei, and the chemical information is lost.ENDOR and ESEEM spectroscopies (3-7) retrieve the missing information. They provide an NMR spectrum of those nuclei that interact with the electron spin of the paramagnetic center, and such spectra display orders-ofmagnitude-better resolution than the

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Compound ES of Cytochrome c Peroxidase Contains a Trp .pi.-Cation Radical: Characterization by Continuous Wave and Pulsed Q-Band External Nuclear Double Resonance Spectroscopy

Cited by 168 publications

References 0 publications

l-Tryptophan Radical Cation Electron Spin Resonance Studies: Connecting Solution-Derived Hyperfine Coupling Constants with Protein Spectral Interpretations

l-Tryptophan Radical Cation Electron Spin Resonance Studies: Connecting Solution-Derived Hyperfine Coupling Constants with Protein Spectral Interpretations

Tyrosine Radical Formation in the Reaction of Wild Type and Mutant Cytochrome P450cam with Peroxy Acids

Electron-nuclear double resonance spectroscopy (and electron spin-echo envelope modulation spectroscopy) in bioinorganic chemistry

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