Issue 18, 2019

Biliverdin–copper complex at physiological pH

Abstract

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

Supplementary files

Article information

Article type
Paper
Submitted
29 nov. 2018
Accepted
04 févr. 2019
First published
04 févr. 2019

Dalton Trans., 2019,48, 6061-6070

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, 48, 6061 DOI: 10.1039/C8DT04724C

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