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Analysis of melanins

Odh Olsson, Gerd LU (1998)
Abstract
Mammalian melanins are of two major types, eumelanins and peheomelanins, which often occur together, then called mixed-type melanins. A method has been developed for analysing the various forms of melanins. Melanin characterisation included their oxidation in permanganate under alkaline conditions, and analysis of the resulting degradation products, pyrrole-2,3,5-tricarboxylic acid (PTCA), pyrrole-2,3-dicarboxylic acid (PDCA) and thiazole-4,5-dicarboxylic acid (TDCA). The PTCA/PDCA ratio manifested correlation with the relative proportions of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI) derived units in melanin, and the TDCA/PTCA+PDCA ratio good correlation with the relative proportions of pheomelanin and... (More)
Mammalian melanins are of two major types, eumelanins and peheomelanins, which often occur together, then called mixed-type melanins. A method has been developed for analysing the various forms of melanins. Melanin characterisation included their oxidation in permanganate under alkaline conditions, and analysis of the resulting degradation products, pyrrole-2,3,5-tricarboxylic acid (PTCA), pyrrole-2,3-dicarboxylic acid (PDCA) and thiazole-4,5-dicarboxylic acid (TDCA). The PTCA/PDCA ratio manifested correlation with the relative proportions of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI) derived units in melanin, and the TDCA/PTCA+PDCA ratio good correlation with the relative proportions of pheomelanin and eumelanin in the pigment. The neuromelanin of the human substantia nigra was found to be of a mixed type, consisting of benzothiazines and indole units in about equal proportions. Melanin from cultures of IGR-1 melanoma cells was also of a mixed type with a eumelanin component ranging from 60 to 85 %. During oxidative stress, the cells manifested increased melanisation accompanied by a shift towards more indole residues with carboxygroups, as reflected by an increased PTCA/PDCA ratio. Fibroblasts transfected with the albino (c) locus gene and the brown (b) locus gene contained an enzyme with tyrosinase activity and another enzyme with dopachrome tautomerase activity. BOTH pheomelanin and eumelanin were synthesised in the transfected fibroblasts. An enzyme isolated from rat liver and human erythrocytes, was found to catalyse the formation of DHI from D-dopachrome. Another enzyme responsible for the tautomerisation of D-dopachrome to DHICA and isolated from the lens of bovine eye was identical with the immunoregolatory factor MIF. These enzymes were found useful in experiments making model melanins were the carboxycontents were predetermined. (Less)
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author
opponent
  • Docent Kågedal, Bertil, University Hospital, Linköping, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
PPT-II, PPT-I, DDT, MIF, tyrosinase related protein. dopachrome tautomerase, 3-dicarboxylic acid, pyrrole-2, 5-tricarboxylic acid, 3, thiazole-4, 5-dicarboxylic acid, Pharmacological sciences, pharmacognosy, pharmacy, toxicology, Farmakologi, farmakognosi, farmaci, toxikologi
pages
146 pages
publisher
Gerd Odh Olsson, Dept of Pharmacology, Sölveg 10, S-223 62 Lund, Sweden,
defense location
Dept. of Pharmacology
defense date
1998-12-09 10:15
external identifiers
  • Other:ISRN LUMEDW/MEFA-1037-SE
language
English
LU publication?
yes
id
714af3aa-ff17-40a3-9a70-bad77330310a (old id 39116)
date added to LUP
2007-07-31 10:59:08
date last changed
2016-09-19 08:45:08
@phdthesis{714af3aa-ff17-40a3-9a70-bad77330310a,
  abstract     = {Mammalian melanins are of two major types, eumelanins and peheomelanins, which often occur together, then called mixed-type melanins. A method has been developed for analysing the various forms of melanins. Melanin characterisation included their oxidation in permanganate under alkaline conditions, and analysis of the resulting degradation products, pyrrole-2,3,5-tricarboxylic acid (PTCA), pyrrole-2,3-dicarboxylic acid (PDCA) and thiazole-4,5-dicarboxylic acid (TDCA). The PTCA/PDCA ratio manifested correlation with the relative proportions of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI) derived units in melanin, and the TDCA/PTCA+PDCA ratio good correlation with the relative proportions of pheomelanin and eumelanin in the pigment. The neuromelanin of the human substantia nigra was found to be of a mixed type, consisting of benzothiazines and indole units in about equal proportions. Melanin from cultures of IGR-1 melanoma cells was also of a mixed type with a eumelanin component ranging from 60 to 85 %. During oxidative stress, the cells manifested increased melanisation accompanied by a shift towards more indole residues with carboxygroups, as reflected by an increased PTCA/PDCA ratio. Fibroblasts transfected with the albino (c) locus gene and the brown (b) locus gene contained an enzyme with tyrosinase activity and another enzyme with dopachrome tautomerase activity. BOTH pheomelanin and eumelanin were synthesised in the transfected fibroblasts. An enzyme isolated from rat liver and human erythrocytes, was found to catalyse the formation of DHI from D-dopachrome. Another enzyme responsible for the tautomerisation of D-dopachrome to DHICA and isolated from the lens of bovine eye was identical with the immunoregolatory factor MIF. These enzymes were found useful in experiments making model melanins were the carboxycontents were predetermined.},
  author       = {Odh Olsson, Gerd},
  keyword      = {PPT-II,PPT-I,DDT,MIF,tyrosinase related protein. dopachrome tautomerase,3-dicarboxylic acid,pyrrole-2,5-tricarboxylic acid,3,thiazole-4,5-dicarboxylic acid,Pharmacological sciences,pharmacognosy,pharmacy,toxicology,Farmakologi,farmakognosi,farmaci,toxikologi},
  language     = {eng},
  pages        = {146},
  publisher    = {Gerd Odh Olsson, Dept of Pharmacology, Sölveg 10, S-223 62 Lund, Sweden,},
  school       = {Lund University},
  title        = {Analysis of melanins},
  year         = {1998},
}