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Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin

Shermiyah B. Rienecker, A. Bernardus Mostert, Gerhard Schenk, Graeme R. Hanson, Paul Meredith Orcid Logo, Bernard Mostert Orcid Logo

The Journal of Physical Chemistry B, Volume: 119, Issue: 48, Pages: 14994 - 15000

Swansea University Authors: Paul Meredith Orcid Logo, Bernard Mostert Orcid Logo

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DOI (Published version): 10.1021/acs.jpcb.5b08970

Abstract

Melanins are pigmentary macromolecules found in many locations throughout nature including plants and vertebrate animals. It was recently proposed that the predominant brown-black pigment eumelanin is a mixed ionic–electronic conductor which has led to renewed interest in its basic properties as a m...

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Published in: The Journal of Physical Chemistry B
ISSN: 1520-6106 1520-5207
Published: 2015
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URI: https://cronfa.swan.ac.uk/Record/cronfa38482
first_indexed 2018-02-09T14:22:18Z
last_indexed 2019-08-09T20:53:15Z
id cronfa38482
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spelling 2019-08-09T15:37:09.9893467 v2 38482 2018-02-09 Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin 31e8fe57fa180d418afd48c3af280c2e 0000-0002-9049-7414 Paul Meredith Paul Meredith true false a353503c976a7338c7708a32e82f451f 0000-0002-9590-2124 Bernard Mostert Bernard Mostert true false 2018-02-09 BGPS Melanins are pigmentary macromolecules found in many locations throughout nature including plants and vertebrate animals. It was recently proposed that the predominant brown-black pigment eumelanin is a mixed ionic–electronic conductor which has led to renewed interest in its basic properties as a model bioelectronic material. This exotic hybrid electrical behavior is strongly dependent upon hydration and is closely related to the free radical content of melanin which is believed to be a mixed population of two species: the semiquinone (SQ) and a carbon-centered radical (CCR). The predominant charge carrier is the proton that is released during the formation of the SQ radical and controlled by a comproportionation equilibrium reaction. In this paper we present a combined solid-state electron paramagnetic resonance (EPR), adsorption, and hydrated conductivity study using D2O as a probe. We make specific predictions as to how the heavy isotope effect, in contrast to H2O, should perturb the comproportionation equilibrium and the related outcome as far as the electrical conductivity is concerned. Our EPR results confirm the proposed two-spin mechanism and clearly demonstrate the power of combining macroscopic measurements with observations from mesoscopic probes for the study of bioelectronic materials. Journal Article The Journal of Physical Chemistry B 119 48 14994 15000 1520-6106 1520-5207 melanin, free radical, electron paramagnetic resonance, heavy water, semiquinone, carbon centered radical 3 12 2015 2015-12-03 10.1021/acs.jpcb.5b08970 This article has been internally assed for REF, 3 star. COLLEGE NANME Biosciences Geography and Physics School COLLEGE CODE BGPS Swansea University 2019-08-09T15:37:09.9893467 2018-02-09T12:45:57.9494086 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics Shermiyah B. Rienecker 1 A. Bernardus Mostert 2 Gerhard Schenk 3 Graeme R. Hanson 4 Paul Meredith 0000-0002-9049-7414 5 Bernard Mostert 0000-0002-9590-2124 6
title Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
spellingShingle Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
Paul Meredith
Bernard Mostert
title_short Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
title_full Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
title_fullStr Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
title_full_unstemmed Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
title_sort Heavy Water as a Probe of the Free Radical Nature and Electrical Conductivity of Melanin
author_id_str_mv 31e8fe57fa180d418afd48c3af280c2e
a353503c976a7338c7708a32e82f451f
author_id_fullname_str_mv 31e8fe57fa180d418afd48c3af280c2e_***_Paul Meredith
a353503c976a7338c7708a32e82f451f_***_Bernard Mostert
author Paul Meredith
Bernard Mostert
author2 Shermiyah B. Rienecker
A. Bernardus Mostert
Gerhard Schenk
Graeme R. Hanson
Paul Meredith
Bernard Mostert
format Journal article
container_title The Journal of Physical Chemistry B
container_volume 119
container_issue 48
container_start_page 14994
publishDate 2015
institution Swansea University
issn 1520-6106
1520-5207
doi_str_mv 10.1021/acs.jpcb.5b08970
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Physics{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Physics
document_store_str 0
active_str 0
description Melanins are pigmentary macromolecules found in many locations throughout nature including plants and vertebrate animals. It was recently proposed that the predominant brown-black pigment eumelanin is a mixed ionic–electronic conductor which has led to renewed interest in its basic properties as a model bioelectronic material. This exotic hybrid electrical behavior is strongly dependent upon hydration and is closely related to the free radical content of melanin which is believed to be a mixed population of two species: the semiquinone (SQ) and a carbon-centered radical (CCR). The predominant charge carrier is the proton that is released during the formation of the SQ radical and controlled by a comproportionation equilibrium reaction. In this paper we present a combined solid-state electron paramagnetic resonance (EPR), adsorption, and hydrated conductivity study using D2O as a probe. We make specific predictions as to how the heavy isotope effect, in contrast to H2O, should perturb the comproportionation equilibrium and the related outcome as far as the electrical conductivity is concerned. Our EPR results confirm the proposed two-spin mechanism and clearly demonstrate the power of combining macroscopic measurements with observations from mesoscopic probes for the study of bioelectronic materials.
published_date 2015-12-03T07:22:29Z
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score 11.364387

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