title: Effect of Cu(2+)-ions on semiconductor properties of synthetic DOPA melanin polymer.
abstract: The purpose of the present study was to examine semiconductor properties of synthetic DOPA melanin, which are basic for future biological applications. DC conductivity, electron spin resonance (ESR), and atomic absorption spectroscopy (AAS) measurements have been performed to investigate the effect of Cu(2+)-ions on the semiconductor properties of melanin polymer synthesized from DOPA (3,4-dihydroxyphenylalanine). DOPA melanin - Cu2+ complexes examined show the decrease of both thermal activation energy delta Ea and pre-exponential factor sigma o values upon doping. At the same time no substantial changes in conductivity at 293 K have been observed. Formation of bipolaron states due to chelation of copper ions by melanin orthosemiquinones has been postulated. The Meyer-Neldel rule with a characteristic temperature T0 equal to 298 K and possible physiological implication of this fact are discussed. These data suggest, that DOPA melanin polymer could be useful as a type of culture substratum.
authors.affiliation: Department of Biochemistry and Biophysics, Silesian Medical Academy, Sosnowiec, Poland.
authors.forename: M M
authors.initials: MM
authors.lastname: Jastrzebska
authors.forename: H
authors.initials: H
authors.lastname: Isotalo
authors.forename: J
authors.initials: J
authors.lastname: Paloheimo
authors.forename: H
authors.initials: H
authors.lastname: Stubb
authors.forename: B
authors.initials: B
authors.lastname: Pilawa
mesh_terms: D001704:Biopolymers; D002118:Calcium; D003300:Copper / Q000737:chemistry*; D019327:Copper Sulfate / Q000737:chemistry; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D004553:Electric Conductivity; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013054:Spectrophotometry, Atomic; D013816:Thermodynamics
chemical_list: D001704:Biopolymers; D004295:Dihydroxyphenylalanine; C040616:DOPA melanin; D003300:Copper; D019327:Copper Sulfate; D002118:Calcium