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UV-Dissipation Mechanisms in the Eumelanin Building Block DHICA.

Huijser, Annemarie LU ; Pezzella, Alessandro; Hannestad, Jonas K; Panzella, Lucia; Napolitano, Alessandra; d'Ischia, Marco and Sundström, Villy LU (2010) In ChemPhysChem 11(11). p.2424-2431
Abstract
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 H(2)O or D(2)O 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 mono-anion 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... (More)
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 H(2)O or D(2)O 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 mono-anion 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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
ChemPhysChem
volume
11
issue
11
pages
2424 - 2431
publisher
John Wiley & Sons
external identifiers
  • wos:000281061500021
  • pmid:20572257
  • scopus:84925287392
ISSN
1439-7641
DOI
10.1002/cphc.201000257
language
English
LU publication?
yes
id
434b512b-14a6-44ad-b0c7-ab24d395fbae (old id 1625770)
date added to LUP
2010-08-25 17:24:13
date last changed
2018-05-29 11:21:19
@article{434b512b-14a6-44ad-b0c7-ab24d395fbae,
  abstract     = {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 H(2)O or D(2)O 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 mono-anion 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.},
  author       = {Huijser, Annemarie and Pezzella, Alessandro and Hannestad, Jonas K and Panzella, Lucia and Napolitano, Alessandra and d'Ischia, Marco and Sundström, Villy},
  issn         = {1439-7641},
  language     = {eng},
  number       = {11},
  pages        = {2424--2431},
  publisher    = {John Wiley & Sons},
  series       = {ChemPhysChem},
  title        = {UV-Dissipation Mechanisms in the Eumelanin Building Block DHICA.},
  url          = {http://dx.doi.org/10.1002/cphc.201000257},
  volume       = {11},
  year         = {2010},
}