PMID- 28195487
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20180205
LR  - 20180205
IS  - 1948-7185 (Electronic)
IS  - 1948-7185 (Linking)
VI  - 8
IP  - 5
DP  - 2017 Mar 2
TI  - Sequential Proton-Coupled Electron Transfer Mediates Excited-State Deactivation 
      of a Eumelanin Building Block.
PG  - 1004-1008
LID - 10.1021/acs.jpclett.6b03012 [doi]
AB  - Skin photoprotection is commonly believed to rely on the photochemistry of 
      5,6-dihydroxyindole (DHI)- and 5,6-dihydroxyindole-2-carboxylic acid 
      (DHICA)-based eumelanin building blocks. Attempts to elucidate the underlying 
      excited-state relaxation mechanisms have been partly unsuccessful due to the 
      marked instability to oxidation. We report a study of the excited-state 
      deactivation of DHI using steady-state and time-resolved fluorescence accompanied 
      by high-level quantum-chemistry calculations including solvent effects. 
      Spectroscopic data show that deactivation of the lowest excited state of DHI in 
      aqueous buffer proceeds on the 100 ps time scale and is 20 times faster than in 
      methanol. Quantum-chemical calculations reveal that the excited-state decay 
      mechanism is a sequential proton-coupled electron transfer, which involves the 
      initial formation of a solvated electron from DHI, followed by the transfer of a 
      proton to the solvent. This unexpected finding would prompt a revision of current 
      notions about eumelanin photophysics and photobiology.
FAU - Nogueira, Juan J
AU  - Nogueira JJ
AD  - Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , 
      Wahringer Str. 17, A-1090 Wien, Austria.
FAU - Corani, Alice
AU  - Corani A
AD  - Department of Chemical Physics, Lund University , Box 124, 22100 Lund, Sweden.
FAU - El Nahhas, Amal
AU  - El Nahhas A
AD  - Department of Chemical Physics, Lund University , Box 124, 22100 Lund, Sweden.
FAU - Pezzella, Alessandro
AU  - Pezzella A
AD  - Department of Chemistry and Sciences, University of Naples Federico II , Via 
      Cintia, 80126 Naples, Italy.
FAU - d'Ischia, Marco
AU  - d'Ischia M
AD  - Department of Chemistry and Sciences, University of Naples Federico II , Via 
      Cintia, 80126 Naples, Italy.
FAU - Gonzalez, Leticia
AU  - Gonzalez L
AUID- ORCID: 0000-0001-5112-794X
AD  - Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna , 
      Wahringer Str. 17, A-1090 Wien, Austria.
FAU - Sundstrom, Villy
AU  - Sundstrom V
AD  - Department of Chemical Physics, Lund University , Box 124, 22100 Lund, Sweden.
LA  - eng
PT  - Journal Article
DEP - 20170216
PL  - United States
TA  - J Phys Chem Lett
JT  - The journal of physical chemistry letters
JID - 101526034
EDAT- 2017/02/15 06:00
MHDA- 2017/02/15 06:01
CRDT- 2017/02/15 06:00
PHST- 2017/02/15 06:00 [pubmed]
PHST- 2017/02/15 06:01 [medline]
PHST- 2017/02/15 06:00 [entrez]
AID - 10.1021/acs.jpclett.6b03012 [doi]
PST - ppublish
SO  - J Phys Chem Lett. 2017 Mar 2;8(5):1004-1008. doi: 10.1021/acs.jpclett.6b03012. 
      Epub 2017 Feb 16.