Quantitative fluorescence spectra and quantum yield map of synthetic pheomelanin

Abstract

Spectroscopic studies of pheomelanin and its constituents have been sparse. These data present what is by far the most complete description of the fluorescence characteristics of synthetic pheomelanin. Emission spectra between 260 and 600 nm were acquired for excitation wavelengths between 250 and 500 nm at 1-nm intervals. A quantum yield map is also presented, correcting the fluorescence intensities for differences in species concentration and molar absorptivity. These fluorescence features exhibit interesting similarities and differences to eumelanin, and these data are interpreted with respect to possible chemical structures. Overall, these data suggest that pheomelanin oligomers may be more tightly coupled than those of eumelanin. Finally, the quantum yield is shown to be on the order of 10(-4) and exhibit a complex dependence on excitation energy, varying by a factor of 4 across the energies employed here.

Anabolic function of phenylalanine hydroxylase inCaenorhabditis elegans

“…ϳ350 nm, and the fluorescence intensity was higher than at basic pH, but also remarkably dependent on the excitation wavelength, disappearing at ϳ300 nm. These fluorescent properties fit quite well with those of natural and synthetic pheomelanin (43,44) and less with those of eumelanin, which does not present the emission band at lower wavelengths (43), or dityrosine, with pH-independent emission maxima and fluorescence intensity (45).…”

“…7B). Featureless broad UV-visible absorption is atypical for organic compounds, which usually display peaks corresponding to specific electronic transitions, but it is characteristic of natural and synthetic melanins, notably of pheomelanin (42)(43)(44). Absorption above 400 nm was negligible, suggesting that the compound is not an eumelanin, which shows a broader monotonic absorbance up to 600 nm (16,44).…”

Mussel-Inspired One-Pot Synthesis of a Fluorescent and Water-Soluble Polydopamine-Polyethyleneimine Copolymer

“…The presence of aggregates of DHI units with different sizes within PDA-PEI permitted the realization of tunable fl uorescence. [54][55][56] The tunability was attributed to the uncontrolled polymerization of DA coupled with PEI. [ 28 ] The excitation wavelength for the PDA-PEI sensing experiments was selected to be 400 nm.…”

Functionality of epidermal melanin pigments: current knowledge on UV-dissipative mechanisms and research perspectives

“…Also the arrangement of the oligomers into a macroscopic structure is at the moment not well understood. [32][33][34] Melanin shows a high affinity for metal ions; metal chelation is often invoked as one of the functions of melanins. [35][36][37][38][39] In particular Simon and co-workers at Duke University have been extensively studying the nature and biological function of metal binding sites.…”