PMID- 20572257
OWN - NLM
STAT- MEDLINE
DCOM- 20101108
LR  - 20131121
IS  - 1439-7641 (Electronic)
IS  - 1439-4235 (Linking)
VI  - 11
IP  - 11
DP  - 2010 Aug 2
TI  - UV-dissipation mechanisms in the eumelanin building block DHICA.
PG  - 2424-31
LID - 10.1002/cphc.201000257 [doi]
AB  - 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.
FAU - Huijser, Annemarie
AU  - Huijser A
AD  - Department of Chemical Physics, Lund University, Box 124, 22100 Lund, Sweden. 
      Annemarie.Huijser@chemphys.lu.se
FAU - Pezzella, Alessandro
AU  - Pezzella A
FAU - Hannestad, Jonas K
AU  - Hannestad JK
FAU - Panzella, Lucia
AU  - Panzella L
FAU - Napolitano, Alessandra
AU  - Napolitano A
FAU - d'Ischia, Marco
AU  - d'Ischia M
FAU - Sundstrom, Villy
AU  - Sundstrom V
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Germany
TA  - Chemphyschem
JT  - Chemphyschem : a European journal of chemical physics and physical chemistry
JID - 100954211
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 0 (Protons)
RN  - 059QF0KO0R (Water)
RN  - 12627-86-0 (eumelanin)
RN  - 4790-08-3 (5,6-dihydroxy-2-indolylcarboxylic acid)
RN  - J65BV539M3 (Deuterium Oxide)
SB  - IM
MH  - Deuterium Oxide/chemistry
MH  - Hydrogen-Ion Concentration
MH  - Indoles/*chemistry/radiation effects
MH  - Melanins/*chemistry
MH  - Protons
MH  - Spectrometry, Fluorescence
MH  - *Ultraviolet Rays
MH  - Water/chemistry
EDAT- 2010/06/24 06:00
MHDA- 2010/11/09 06:00
CRDT- 2010/06/24 06:00
PHST- 2010/06/24 06:00 [entrez]
PHST- 2010/06/24 06:00 [pubmed]
PHST- 2010/11/09 06:00 [medline]
AID - 10.1002/cphc.201000257 [doi]
PST - ppublish
SO  - Chemphyschem. 2010 Aug 2;11(11):2424-31. doi: 10.1002/cphc.201000257.