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Determination of the formal redox potentials of the cyanhaemoglobin/cyanmethaemoglobin and the myoglobin/metmyoglobin couples at neutral pH


Mahmoudi, Leila; Zelder, Felix; Kissner, Reinhard (2018). Determination of the formal redox potentials of the cyanhaemoglobin/cyanmethaemoglobin and the myoglobin/metmyoglobin couples at neutral pH. Bioelectrochemistry, 120:83-86.

Abstract

Determination of a representative formal redox potential of the Fe(II)/Fe(III) redox couple in cyanhaemoglobin, at pH = 7 and related to the state in solution, was the objective of this work. It was achieved at low concentrations of the protein (5 μM) to circumvent undesired adsorption. Square-wave voltammetry instead of classical cyclic voltammetry was applied because this method is more sensitive and provides information on the formal redox potential and reversibility, even for rapid processes. We obtained E°′ = − 0.12 ± 0.01 V for cyanhaemoglobin and E°′ = − 0.10 ± 0.01 V, vs. SHE, for myoglobin in comparison. These values differ by only 20 mV because the two Fe(II)/Fe(III) redox centres are embedded in closely resembling chemical environments. The small difference is probably owed to the additional axially coordinating cyanide ligand in cyanmethaemoglobin which slightly favours the Fe(III) state in the haem macrocycle.

Abstract

Determination of a representative formal redox potential of the Fe(II)/Fe(III) redox couple in cyanhaemoglobin, at pH = 7 and related to the state in solution, was the objective of this work. It was achieved at low concentrations of the protein (5 μM) to circumvent undesired adsorption. Square-wave voltammetry instead of classical cyclic voltammetry was applied because this method is more sensitive and provides information on the formal redox potential and reversibility, even for rapid processes. We obtained E°′ = − 0.12 ± 0.01 V for cyanhaemoglobin and E°′ = − 0.10 ± 0.01 V, vs. SHE, for myoglobin in comparison. These values differ by only 20 mV because the two Fe(II)/Fe(III) redox centres are embedded in closely resembling chemical environments. The small difference is probably owed to the additional axially coordinating cyanide ligand in cyanmethaemoglobin which slightly favours the Fe(III) state in the haem macrocycle.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Uncontrolled Keywords:Physical and Theoretical Chemistry, Biophysics, Electrochemistry, General Medicine
Language:English
Date:2018
Deposited On:09 Feb 2018 08:01
Last Modified:19 Aug 2018 13:49
Publisher:Elsevier
ISSN:1567-5394
OA Status:Closed
Publisher DOI:https://doi.org/10.1016/j.bioelechem.2017.11.012

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