A1 Refereed original research article in a scientific journal
Effects of pH and Oxidants on the First Steps of Polydopamine Formation: A Thermodynamic Approach
Authors: Mikko Salomäki, Lauri Marttila, Henri Kivelä, Tuomo Ouvinen, Jukka Lukkari
Publisher: AMER CHEMICAL SOC
Publication year: 2018
Journal: Journal of Physical Chemistry B
Journal name in source: JOURNAL OF PHYSICAL CHEMISTRY B
Journal acronym: J PHYS CHEM B
Volume: 122
Issue: 24
First page : 6314
Last page: 6327
Number of pages: 14
ISSN: 1520-6106
DOI: https://doi.org/10.1021/acs.jpcb.8b02304
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/32140450
We present a general thermodynamic top-down analysis of the effects of oxidants and pH on dopamine oxidation and cyclization, supplemented with UV-vis and electrochemical studies. The model is applicable to other catecholamines and various experimental conditions. The results show that the decisive physicochemical parameters in autoxidation are the pK values of the semiquinone and the amino group in the oxidized quinone. Addition of Ce(IV) or Fe(III) enhances dopamine oxidation in acidic media in aerobic and anaerobic conditions by the direct oxidation of dopamine and, in the presence of oxygen, also by the autoxidation of the formed semiquinone. At pH 4.5, the enhancement of the one-electron oxidation of dopamine explains the overall reaction enhancement, but at a lower pH, cyclization becomes rate-determining. Oxidation by Cu(II) at reasonable rates requires the presence of oxygen or chloride ions.
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