Precision of quantitative electron spin resonance using copper(II) bound to ion-exchange resins

Warren, Doris C.; Fitzgerald, J. M.

doi:10.1021/ac50010a018

Cited by 30 publications

(7 citation statements)

References 12 publications

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“…It is possible that a spin-spin interaction exists between the reduced iron-sulfur cluster and FAD semiquinone, but we were unable to detect any EPR line-shape distortion which would indicate this interaction. A 5-10% error inherent in any quantitative EPR measurement because of instrumental limitations (Warren & Fitzgerald, 1977) may also account, at least in part, for the discrepancy. Due to the uncertainty introduced by the substoichiometric cluster quantitation, we estimate that an error of ±0.010 V exists in the formal potential value determination of the iron-sulfur cluster in ETF-QO.…”

Section: Resultsmentioning

confidence: 99%

Redox properties of electron-transfer flavoprotein ubiquinone oxidoreductase as determined by EPR-spectroelectrochemistry

et al. 1992

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We have determined the formal potential values for each electron transfer to electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO), in order to further characterize the thermodynamics of electron transport from various acyl-CoA thioesters to the mitochondrial ubiquinone pool. ETF-QO contains one [4Fe-4S]2+,1+ cluster and one FAD prosthetic group. A preliminary visible-spectroelectrochemical titration showed that the two redox centers were reduced almost simultaneously. Since the visible spectra of the chromophores overlap, it was not possible to resolve the formal potential value for each electron transfer to the protein using this method. Accordingly, an EPR-spectroelectrochemical cell was designed so that each formal potential value could be resolved by EPR quantitation of the flavin semiquinone and the reduced iron-sulfur cluster during the titration. The formal potential values for electron transfer to ETF-ubiquinone oxidoreductase at pH 7.5 and 4 degrees C were E1 degrees' = +0.028 V and E2 degrees' = -0.006 V for the first and second electron transfers, respectively, to the FAD and E degrees' = +0.047 V for the iron-sulfur cluster. The thermodynamics of electron transport from the acyl-CoA substrates of beta-oxidation to the mitochondrial electron transport chain have been fully resolved with completion of this work. The results are discussed in terms of their significance to the overall electron transport process from beta-oxidation.

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Section: Resultsmentioning

confidence: 99%

Redox properties of electron-transfer flavoprotein ubiquinone oxidoreductase as determined by EPR-spectroelectrochemistry

et al. 1992

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“…Later on this was found to be incorrect and the effect of a changing linewidth was accounted for in rather complicated ways. We preferred to derive a so-called intensity parameter, IP, which takes into account both the height and width of the chosen line and is proportional to the signal area (Poole 1983, 443-50;Warren and Fitzgerald 1977). Such a parameter is defined as Wi, * h IP = K R G S M A -m and refers to unitary mass, gain, and modulation amplitude.…”

Section: Esr Data Analysismentioning

confidence: 99%

Electron Spin Resonance Study of White Marbles From Tharros (Sardinia): A Reappraisal of the Technique, Possibilities and Limitations*

1997

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The characterization of various samples of white marble from the archaeological site of Tharros (Sardinia) is the starting point for the reexamination of the capabilities of electron spin resonance (ESR) spectroscopy as a tool for identifying the quarries of origin of ancient marble artefacts. Existing methods and data bases are employed for the assignment of our samples, but also reviewed to see if a more extensive use of the technique is feasible. It turns out that ESR spectroscopy, coupled with other available methods, may readily provide valuable information, often yielding the final answer to the problem of marble provenance. However, it is also clear that much work has still to be done to standardize the data collection and analysis procedures and to expand the available data base.

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“…The contribution of these uncertainties has been estimated to be 15% in 1965, decreased to about 10% in 1977 and recent considerations have shown that their contribution is reduced to about 3-5% [27][28][29][30]. This improvement is due to continuous application of the advanced technologies products in modern EPR spectrometers.…”

Section: Instrumentation Cavities Sample Ceus and Samplesmentioning

confidence: 99%

Quantitative EPR spectrometry — “State of the art”

Yordanov

1994

Appl. Magn. Reson.

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Precision of quantitative electron spin resonance using copper(II) bound to ion-exchange resins

Cited by 30 publications

References 12 publications

Redox properties of electron-transfer flavoprotein ubiquinone oxidoreductase as determined by EPR-spectroelectrochemistry

Redox properties of electron-transfer flavoprotein ubiquinone oxidoreductase as determined by EPR-spectroelectrochemistry

Electron Spin Resonance Study of White Marbles From Tharros (Sardinia): A Reappraisal of the Technique, Possibilities and Limitations*

Quantitative EPR spectrometry — “State of the art”

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