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EPR study of melanin-protein interaction: Photoinduced free radicals and progressive microwave power saturation

✍ Scribed by Pedro Geraldo Pascutti; Amando Siuiti Ito

Book ID
103993321
Publisher
Elsevier Science
Year
1992
Tongue
English
Weight
689 KB
Volume
16
Category
Article
ISSN
1011-1344

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✦ Synopsis

The photo-induction of free radicals in synthetic L-dihydroxyphenylalanine (L-DOPA) melanin in the presence of bovine serum albumin (BSA) was studied by electron paramagnetic resonance (EPR) spectroscopy. By monitoring the signal intensities and progressive microwave power saturation it was shown that L-DOPA melanin in solution behaves as a single macromolecule, interacting with BSA and molecular oxygen. In the absence of oxygen, the EPR signal of L-DOPA melanin was homogeneously broadened; the magnetic interaction with oxygen induced inhomogeneous broadening. In aqueous solution, the presence of BSA decreased the accessibility of oxygen to paramagnetic centres in the melanin. On UV-visible illumination, the presence of BSA modified the rates of formation and decay of photoinduced free radicals, resulting in a net enhancement of the EPR signal compared with that observed in pure L-DOPA melanin.

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