@conference{
author = "Dimitrijević, Milena and Bogdanović Pristov, Jelena and Žižić, Milan and Stanković, Dalibor and Bajuk-Bogdanović, Danica and Stanić, Marina and Hagen, Wilfred and Piccioli, Mario and Spasojević, Ivan",
year = "2019",
abstract = "The structure of biliverdin (BV) and its complexion capacity with Cu2+ in dependence of
solvent choice has been examined. We first examined coordinate/redox interactions of BV
with Cu2+ in phosphate buffer at pH 7.4, using spectrophotometry, HESI-MS, Raman
spectroscopy, 1HNMR, 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 longstanding
question of high energy investment in the catabolism of BV, which represents a
relatively harmless molecule per se. The complex possibility was quite different after
changing the solvent. BV structure in DMSO was analyzed by using NMR techniques and
unrestricted density function theory simulations to explain the incapacity of BV to build
coordination complex(es) with Cu2+ in dimethyl sulfoxide, which was confirmed by UV-Vis,
EPR and NMR spectroscopy. NMR showed that N atoms of BV are protonated in all four
pyrrole rings. The structure is stabilized by two hydrogen bonds between NH moieties and
carbonyl oxygens from opposite terminal pyrrole rings, and by the bending of propionyl chain
with carboxyl group out of the plain toward central position of BV. The simulations of
deprotonated BV, which builds copper complexes in water and chloroform as described
previously, showed a different conformation and organization of hydrogen bonds. Taking into
account that deprotonation represents a critical step in coordinate bonds formation, the
protonation of an additional N atom may represent a key difference between the interactions
of BV with copper in different solvents.",
publisher = "COST Action CA15133",
journal = "Book of abstracts: 4th FeSBioNet Meeting: COST Action CA15133; 2019 Sep 16-19; Gdansk, Poland",
title = "Structure of biliverdin and its interaction with copper",
pages = "44-44",
url = "https://hdl.handle.net/21.15107/rcub_rimsi_3187"
}
