ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P46. Synthesis, Spectroscopic Characterization and Catalytic Activity of
Neuromelanin Models Containing Albumin and Metal Ions
M. Engelen, E. Ferrari, E. Monzani, L. Casella
Department of Chemistry, University of Pavia, Via Taramelli 12, 27100, Pavia, Italy
Neuromelanin is a partially characterized pigment found primarily in catecholaminergic neurons[1,2]. Although
its composition and function are not completely understood, the pigment seems to be involved in the
development of neurodegenerative diseases such as Alzheimer′s and Parkinson′s disease [3,4]. One of the
difficulties concerning the complete characterization of neuromelanin is the scarcity of biological material, as
well as the poor solubility in non-destructive solvents [5].
To gain a better understanding of neuromelanin structure, several synthetic melanins, containing different
amounts of albumin and iron or copper ions to simulate the natural product, have been synthesized and
characterized by NMR, UV-VIS, EPR and CD spectroscopy. At higher concentrations of albumin the products
remain soluble in H2O, which semplifies the characterization process. Surprisingly, the synthetic melanins
display catalytic activity in the oxidation of dopamine to dopamine quinone. The presence of Fe II or Cu II ions in
the pigment increases the catalytic activity, but metal ions sequestered by the macromolecule have a much lower
activity compared to free metal ions in solution. This seems to confirm the hypothesis that neuromelanin might
play a protective role by sequestering redox active metals from its surroundings[6]. However, since the activity
of the metal ions is not completely blocked, the pigment can not be considered inert and over long periods of
time might cause oxidative stress.
References:
[1] L. Zecca, P. Costi, C. Mecacci, S. Ito, M. Terreni, S. Sonnino, J.Neurochem., 74, 1758 (2000).
[2] L. Zecca, T. Shima, A. Stroppolo, C. Goj, G.A. Battistoni, R. Gerbasi, T. Sarna, H.M. Swartz, Neuroscience,
73, 407 (1996).
[3] M. Fasano, B. Bergamasco, L. Lopiano, J. Neural Transm., 113, 769 (2006).
[4] L. Zecca, F.A. Zucca, H. Wilms, D. Sulzer, Trends in neurosciences, 26, 578 (2003).
[5] K.L. Double, et al., J. Neurochem., 75, 2583 (2000).
[6] L. Zecca, D. Tampellini, M. Gerlach, P. Riederer, R.G. Fariello,D. Sulzer, J. Clin. Pathol.: Mol. Pathol., 54,
414 (2001).
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