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Biliverdin–copper complex at physiological pH

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Biliverdin (BV), a product of heme catabolism, is known to interact with transition metals, but the details of such interactions under physiological conditions are scarce. Herein, we examined coordinate/redox interactions of BV with Cu2+ in phosphate buffer at pH 7.4, using spectrophotometry, HESI-MS, Raman spectroscopy, 1H NMR, EPR, fluorimetry, and electrochemical methods. BV formed a stable coordination complex with copper in 1 : 1 stoichiometry. The structure of BV was more planar and energetically stable in the complex. The complex showed strong paramagnetic effects that were attributed to an unpaired delocalized e. The delocalized electron may come from BV or Cu2+, so the complex is formally composed either of BV radical cation and Cu1+ or of BV radical anion and Cu3+. The complex underwent oxidation only in the presence of both O2 and an excess of Cu2+, or a strong oxidizing agent, and it was resistant to reducing agents. The biological effects of the stable BV metallocomplex containing a delocalized unpaired electron should be further examined, and may provide an answer to the long-standing question of high energy investment in the catabolism of BV, which represents a relatively harmless molecule per se.

Graphical abstract: Biliverdin–copper complex at physiological pH

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The article was received on 29 Nov 2018, accepted on 04 Feb 2019 and first published on 04 Feb 2019

Article type: Paper
DOI: 10.1039/C8DT04724C
Citation: Dalton Trans., 2019, Advance Article

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    Biliverdin–copper complex at physiological pH

    M. S. Dimitrijević, J. Bogdanović Pristov, M. Žižić, D. M. Stanković, D. Bajuk-Bogdanović, M. Stanić, S. Spasić, W. Hagen and I. Spasojević, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C8DT04724C

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