1. A systematic survey of the reactions of compounds containing the functional groups of proteins with melanogenic systems comprised of o-diphenol oxidase and catechol, 4-methylcatechol, 3,4-dihydroxyphenylalanine, or 5,6-dihydroxyindole, has been carried out with an automatic recording rapid-scanni...
1. A systematic survey of the reactions of compounds containing the functional groups of proteins with melanogenic systems comprised of o-diphenol oxidase and catechol, 4-methylcatechol, 3,4-dihydroxyphenylalanine, or 5,6-dihydroxyindole, has been carried out with an automatic recording rapid-scanning spectrophotometer.2. The 3-substituted indole ring, the amide group, the ureido and guanidino groupings, seryl hydroxyl, and 4-substituted imidazole groups do not react with any of the quinones derived by enzymic oxidation of the catecholic melanogens, according to spectroscopic criteria.3. N-terminal primary amino groups, aliphatic amino groups, secondary amines in amino acids, and thiol-containing amino acids react with o-benzoquinone and 4-methyl-o-benzoquinone to give intermediates with characteristic absorption spectra.4. Only thiol-containing compounds (and aromatic amines) react with melanogenic quinones derived from 3,4-dihydroxyphenylalanine to produce intermediates with characteristic absorption spectra. These reactions appear to involve ''indole-5,6-quinone'' only.5. A new melanochrome or leucomelanochrome which forms during the polymerization of indole-5,6-quinone to melanin, has been observed.
1. A systematic survey of the reactions of compounds containing the functional groups of proteins with melanogenic systems comprised of o-diphenol oxidase and catechol, 4-methylcatechol, 3,4-dihydroxyphenylalanine, or 5,6-dihydroxyindole, has been carried out with an automatic recording rapid-scanning spectrophotometer.2. The 3-substituted indole ring, the amide group, the ureido and guanidino groupings, seryl hydroxyl, and 4-substituted imidazole groups do not react with any of the quinones derived by enzymic oxidation of the catecholic melanogens, according to spectroscopic criteria.3. N-terminal primary amino groups, aliphatic amino groups, secondary amines in amino acids, and thiol-containing amino acids react with o-benzoquinone and 4-methyl-o-benzoquinone to give intermediates with characteristic absorption spectra.4. Only thiol-containing compounds (and aromatic amines) react with melanogenic quinones derived from 3,4-dihydroxyphenylalanine to produce intermediates with characteristic absorption spectra. These reactions appear to involve ''indole-5,6-quinone'' only.5. A new melanochrome or leucomelanochrome which forms during the polymerization of indole-5,6-quinone to melanin, has been observed.
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