PMID- 2804118
OWN - NLM
STAT- MEDLINE
DCOM- 19891204
LR  - 20190609
IS  - 0006-3002 (Print)
IS  - 0006-3002 (Linking)
VI  - 993
IP  - 1
DP  - 1989 Oct 13
TI  - A pulse radiolysis investigation of the oxidation of indolic melanin precursors: 
      evidence for indolequinones and subsequent intermediates.
PG  - 12-20
AB  - The rate constants associated with the series of successive transient absorptions 
      initiated by one-electron oxidation of 5,6-dihydroxyindole (DHI), 
      5,6-dihydroxyindole-2-carboxylic acid (DHICA), precursors of melanin, and 
      N-methyl-5,6-dihydroxyindole (NMDHI), a model compound, have been studied by 
      pulse radiolysis. The initial transient species resulting from N3. oxidation 
      reaction at pH 7.3-7.4 are assigned as the corresponding semiquinones. In each 
      case, these radicals decayed, probably by disproportionation, into products most 
      readily monitored in the 400-430 nm region. For DHI, the decay in this region 
      could be fitted by two parent concentration independent first-order processes. 
      These may correspond to transformations between 5,6-indolequinone, and its 
      quinone-imine and quinone-methide tautomers. With NMDHI, on the other hand, a 
      single longer-lived product with a peak around 430 nm predominated after decay of 
      the corresponding radical, due almost certainly to N-methyl-5,6-indolequinone. 
      The data appear to exclude significant melanin polymerisation by condensation of 
      semiquinones, reaction of semiquinones with dihydroxyindoles, self-addition of 
      indolequinones or tautomers, or reaction of indolequinones or tautomers with the 
      parent dihydroxyindoles. It is suggested that polymerisation of melanin may 
      rather occur by stepwise addition of indolequinone methide/imine to reduced 
      oligomeric species.
FAU - Lambert, C
AU  - Lambert C
AD  - Paterson Institute for Cancer Research, Christie Hospital and Holt Radium 
      Institute, Manchester, UK.
FAU - Chacon, J N
AU  - Chacon JN
FAU - Chedekel, M R
AU  - Chedekel MR
FAU - Land, E J
AU  - Land EJ
FAU - Riley, P A
AU  - Riley PA
FAU - Thompson, A
AU  - Thompson A
FAU - Truscott, T G
AU  - Truscott TG
LA  - eng
GR  - AG02380/AG/NIA NIH HHS/United States
GR  - AG02381/AG/NIA NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - Netherlands
TA  - Biochim Biophys Acta
JT  - Biochimica et biophysica acta
JID - 0217513
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 0 (Quinones)
RN  - 0 (Thiocyanates)
RN  - 4790-08-3 (5,6-dihydroxy-2-indolylcarboxylic acid)
RN  - 4821-00-5 (N-methyl-5,6-dihydroxyindole)
RN  - TM7213864A (potassium thiocyanate)
RN  - Z3OC8499KG (5,6-dihydroxyindole)
SB  - IM
MH  - *Indoles
MH  - Kinetics
MH  - *Melanins
MH  - Molecular Structure
MH  - Oxidation-Reduction
MH  - *Quinones
MH  - Spectrophotometry
MH  - Structure-Activity Relationship
MH  - Thiocyanates
EDAT- 1989/10/13 00:00
MHDA- 1989/10/13 00:01
CRDT- 1989/10/13 00:00
PHST- 1989/10/13 00:00 [pubmed]
PHST- 1989/10/13 00:01 [medline]
PHST- 1989/10/13 00:00 [entrez]
AID - 0304-4165(89)90136-0 [pii]
AID - 10.1016/0304-4165(89)90136-0 [doi]
PST - ppublish
SO  - Biochim Biophys Acta. 1989 Oct 13;993(1):12-20. doi: 
      10.1016/0304-4165(89)90136-0.