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Biliverdin-copper complex at physiological pH

By Milena S. Dimitrijević, Jelena Bogdanović-Pristov, Milan Žižić, Dalibor M. Stanković, Danica V. Bajuk-Bogdanović, Marina Stanić, Snežana D. Spasić, Wilfred Hagen and Ivan Spasojević

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, 1 H 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.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3069]This is the peer-reviewed version of the following article: Dimitrijević, M. S.; Bogdanović Pristov, J.; Žižić, M.; Stanković, D. M.; Bajuk-Bogdanović, D.; Stanić, M.; Spasić, S.; Hagen, W.; Spasojević, I. Biliverdin-Copper Complex at Physiological PH. Dalton Transactions 2019, 48 (18), 6061–6070. [https://doi.org/10.1039/c8dt04724c

Year: 2019
DOI identifier: 10.1039/c8dt04724c
OAI identifier: oai:vinar.vin.bg.ac.rs:123456789/8258
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