Journal
CHEMPHYSCHEM
Volume 11, Issue 11, Pages 2424-2431Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cphc.201000257
Keywords
eumelanin; DHICA; isotope effects; proton transfer; time-resolved fluorescence
Funding
- Wenner-Gren Foundation
- Swedish Energy Agency
- Knut and Alice Wallenberg Foundation
- Swedish Research Council
- Italian MIUR [LMY5WX]
- European Science Foundation (ESF)
Ask authors/readers for more resources
The UV-dissipative mechanisms of the eumelanin building block 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and the 4,7-dideutero derivative (DHICA-d(2)) in buffered H2O or D2O have been characterized by using ultrafast time-resolved fluorescence spectroscopy. Excitation of the carboxylate anion form, the dominating state at neutral pH, leads to dual fluorescence. The band peaking at lambda = 378 nm is caused by emission from the excited initial geometry. The second band around lambda = 450 nm is owed to a complex formed between the monoanion and specific buffer components. In the absence of complex formation, the mono-anion solely decays non-radiatively or by emission with a lifetime of about 2.1 ns. Excitation of the neutral carboxylic acid state, which dominates at acidic pH, leads to a weak emission around lambda = 427 nm with a short lifetime of 240 ps. This emission originates from the zwitterionic state, formed upon excitation of the neutral state by sub-ps excited-state intramolecular proton transfer (ESIPT) between the carboxylic acid group and the indole nitrogen. Future studies will unravel whether this also occurs in larger building blocks and ESIPT is a built-in photoprotective mechanism in epidermal eumelanin.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available