Time-resolved EPR investigation of oxygen and temperature effects on synthetic eumelanin

Issue title: From Molecule to Tissue: XIII European Conference on the Spectroscopy of Biological Molecules, Palermo, Italy, August 28–September 2, 2009, Part 2 of 2

Article type: Research Article

Authors: Conti, Fosca^; | Panzella, Lucia | Napolitano, Alessandra | d'Ischia, Marco | Toffoletti, Antonio

Affiliations: Department of Chemical Sciences, University of Padova, Padova, Italy | Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Naples, Italy

Note: [] Corresponding author: Dr. Fosca Conti, Department of Chemical Sciences, University of Padova, via Marzolo 1, I-35131 Padova, Italy. E-mail: [email protected].

Abstract: Synthetic eumelanin produced using 5,6-dihydroxyindole-2-carboxylic acid as precursor and H2O2/horseradish peroxidase as oxidative reagent, in form of dry powder, has been investigated under photoexcitation by TR-EPR spectroscopy. The formation of spin polarized radical pairs from triplet excited states of melanin has been observed both in absence and in presence of oxygen and has been followed as a function of the temperature in the range 140–290 K. The triplet mechanism explains the observed polarization pattern in net emission. In the presence of oxygen new radical pairs are formed by interaction of melanin with molecular oxygen.

Keywords: Melanin, DHICA, EPR spectroscopy, radical pair, spin polarization, excited state, superoxide radical anion

DOI: 10.3233/SPE-2010-0430

Journal: Spectroscopy, vol. 24, no. 3-4, pp. 289-295, 2010