An electroreflectance approach to study out the puzzling state of myoglobin in a DDAB film on a pyrolytic graphite electrode surface

Sagara, Takamasa; Sakai, Tomomi; Nagatani, Hirohisa

doi:10.1016/j.elecom.2007.05.022

Cited by 4 publications

(9 citation statements)

References 18 publications

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“…On the basis of UV−vis spectroscopy measurements, the addition of NaBr salt to the DDAB dispersion was proposed to help stabilize the DDAB bilayer structure and thereby assist the retention of myoglobin in its near-native conformation. However, a recent report by Sagara et al failed to confirm the stabilization effect …”

Section: Resultsmentioning

confidence: 92%

“…Koper et al proposed that the release of heme from myoglobin molecules is enhanced by the interaction with the graphite surface. , Rusling et al disagree with this view . Recently, results published by Sagara et al suggested that heme release may occur even before casting the DDAB films on a pyrolytic graphite electrode …”

Section: Resultsmentioning

confidence: 99%

“…It has been suggested that myoglobin incorporated into a DDAB film is likely to form an ordered bilayer structure. If this hypothesis is correct, this matrix should allow retention of the near-native conformation of myoglobin molecules and also prevent adsorption of impurities from solutions which could otherwise block electron transfer between myoglobin and the electrode. − The major roles of the DDAB host film, including the ability to retain the intact secondary myoglobin structure were accepted until a report of a heme-release hypothesis by Koper and co-workers which triggered intense debate on the state of the heme center of myoglobin when present in a DDAB film adhered to a pyrolytic graphite electrode surface. − …”

Section: Introductionmentioning

confidence: 99%

“…Various analytical techniques such as dc cyclic voltammetry, UV−vis absorption spectroscopy, circular dichroism spectroscopy, and electroreflectance spectroscopy have been employed to examine the state of myoglobin molecules in DDAB host films adhered to a pyrolytic graphite electrode surface. − Unfortunately, highly informative techniques such as surface-enhanced resonance Raman spectroscopy and surface-enhanced infrared difference adsorption spectroscopy, which are commonly employed to probe the protein conformations, are difficult to employ when myoglobin-DDAB films are adhered to pyrolytic graphite. This is because of unfavorable light absorbance characteristics of this electrode material.…”

Section: Introductionmentioning

confidence: 99%

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A Comparison of the Higher Order Harmonic Components Derived from Large-Amplitude Fourier Transformed ac Voltammetry of Myoglobin and Heme in DDAB Films at a Pyrolytic Graphite Electrode

Lee

Bond

2010

Langmuir

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A debate as to whether heme remains bound or is released in myoglobin molecules incorporated into a didodecyldimethylammonium bromide (DDAB) film adhered to a pyrolytic graphite electrode has prompted a comparison of their electrochemistry by the highly sensitive large-amplitude Fourier transformed ac voltammetric method. The accessibility of third, fourth, and higher harmonic components that are devoid of background current and the enhanced resolution relative to that available in dc voltammetry have allowed a detailed comparison of the Fe(III)/Fe(II) and Fe(II)/Fe(I) redox processes of myoglobin and heme molecules to be undertaken as a function of buffer composition and pH and in the presence and absence of NaBr in the buffer and/or film. Under most conditions examined, only very subtle differences, in the Fe(III)/Fe(II) process were found, implying this process cannot be used to indicate the intactness or otherwise of myoglobin in myoglobin-DDAB films. In contrast, higher order ac harmonics obtained from myoglobin-DDAB and heme-DDAB films reveal pH dependent differences with respect to the Fe(II)/Fe(I) couple. Analysis of the ac harmonics, and with the hypothesis that the Fe(II)/Fe(I) process reflects the myoglobin state, suggests that the majority of the iron heme is released from myoglobin-DDAB (pH 5.0, no NaBr) films in contact with pH 5.0 (0.1 M sodium acetate) buffer solution devoid of or containing NaBr. However, myoglobin films prepared with pH 5.0 buffer containing NaBr shows significant difference in the higher harmonic shapes and midpoint potentials in the Fe(II)/Fe(I) process relative to the case when heme molecules are used, although as noted in other studies, a significant fraction of the Mb is rendered electroinactive in the presence of NaBr. The voltammetric responses of myoglobin and heme-DDAB (pH 5.0) films in contact with pH 7.0 (0.1 M) phosphate buffer solution also exhibit significant differences in the Fe(II)/Fe(I) redox couple in the higher harmonics in contrast to a report [de Groot, M.T.; Merkx, M.; Koper, M. T. M. J. Am. Chem. Soc. 2005, 127, 16224] that claimed identical midpoint potentials apply to both films under conditions of dc cyclic voltammetry. The FT-ac voltammetric data therefore suggest that a substantial fraction of myoglobin in myoglobin-DDAB (pH 5.0) films in contact with pH 7.0 phosphate buffer solution remains intact. No evidence of a catalytic effect that enhanced the released of heme from myoglobin was found at the pyrolytic graphite electrode surface. In summary, higher harmonic ac voltammetric data indicate that the Fe(II)/Fe(I) process but not the Fe(III)/Fe(II) reflects the state of myoglobin in DDAB films. On this basis, films prepared at pH 5.0 should include NaBr, or else films should be prepared at neutral pH to achieve films with myoglobin remains in its intact near native state when a myoglobin-DDAB film is confined to a graphite electrode surface. Otherwise, the release of heme in myoglobin molecules incorporated into a DDAB film is likely to be a dominant...

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Comparison of the Higher Order Harmonic Components Derived from Large-Amplitude Fourier Transformed ac Voltammetry of Myoglobin and Heme in DDAB Films at a Pyrolytic Graphite Electrode

Lee

Bond

2010

Langmuir

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“…This was later disputed by Guto and Rusling , but Sagara et al. supported the conclusions of De Groot. Their data were consistent with heme release by conformation change caused by DDAB.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Reduction of Bisulfite by Myoglobin/Surfactant Films

Abdelatty

Rahman

2017

Electroanalysis

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The voltammetry of bisulfite at a film formed with myoglobin was studied in aqueous solutions. A broad wave was observed for the reduction of bisulfite. Using controlled potential electrolysis, the reduction at potentials positive of the FeII/FeI wave formed dithionite exclusively. As the potential approached the region for the FeII/FeI reduction, bisulfite was reduced primarily to HS−. Even at the negative potentials, some dithionite was still formed, which could then be electrochemically reduced to thiosulfate. Analysis of the formation of HS−, dithionite and thiosulfate during the electrolysis was consistent with the parallel formation of HS− and dithionite, the latter of which was reduced to thiosulfate. Thiosulfate was verified by chemical analysis of the products from controlled potential electrolysis of the solution, and dithionite was observed spectroscopically using spectroelectro−chemistry.

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