title: Effect of stacking and redox state on optical absorption spectra of melanins -- comparison of theoretical and experimental results.
abstract: In this work the effect of aggregation and oxidation on the optical absorption of eumelanin oligomeric sheets is investigated by applying quantum mechanics and atomistic simulation studies to a simplified eumelanin structural model that includes 1-3 sheets of hexameric oligomer sheets. The oligomeric hypothesis is supported by AFM characterizations of synthetic eumelanins, formed by auto-oxidation or electrochemical oxidation of dihydroxyindole (DHI). Comparison of calculated absorption spectra to experimental spectra demonstrates a red shift in absorption with oxidation and stacking of the eumelanin and validates the theoretical results.
authors.affiliation: Accelrys Incorporated, 1042 Kress Street, Houston, Texas 77020, USA. kstark@accelrys.com
authors.forename: Klaus B
authors.initials: KB
authors.lastname: Stark
authors.forename: James M
authors.initials: JM
authors.lastname: Gallas
authors.forename: Gerry W
authors.initials: GW
authors.lastname: Zajac
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Golab
authors.forename: Shirley
authors.initials: S
authors.lastname: Gidanian
authors.forename: Theresa
authors.initials: T
authors.lastname: McIntire
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Farmer
mesh_terms: D002627:Chemistry, Physical / Q000379:methods*; D004563:Electrochemistry; D006860:Hydrogen Bonding; D007211:Indoles / Q000737:chemistry; D008543:Melanins / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods
chemical_list: D007211:Indoles; D008543:Melanins; C041877:eumelanin; D010100:Oxygen