Linked Life Data

18435615

Source:http://linkedlifedata.com/resource/pubmed/id/18435615

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2008-4-25
pubmed:abstractText
The characteristic absorption and photochemical properties of pheomelanins are generally attributed to "benzothiazine" structural units derived biogenetically from 5-S-cysteinyldopa. This notion, however, conveys little or no information about the structural chromophores responsible for the photoreactivity of pheomelanins. At pH 7.4, natural and synthetic pheomelanins show a defined maximum around 305 nm, which is not affected by reductive treatment with sodium borohydride, and a monotonic decrease in the absorption in the range 350-550 nm. These features are not compatible with a significant proportion of structural units related to 2H-1,4-benzothiazine and 2H-1,4-benzothiazine-3-carboxylic acid, the early borohydride-reducible pheomelanin precursors featuring absorption maxima above 340 nm. Rather, these features would better accommodate a contribution by the nonreducible 3-oxo-3,4-dihydrobenzothiazine (lambdamax 299 nm) and benzothiazole (lambdamax 303 nm) structural motifs, which are generated in the later stages of pheomelanogenesis in vitro. This conclusion is supported by a detailed liquid chromatography/UV and mass spectrometry monitoring of the species formed in the oxidative conversion of 5-S-cysteinyldopa to pheomelanin, and would point to a critical reassessment of the commonly reported "benzothiazine" chromophore in terms of more specific and substantiated structural units, like those formed during the later stages of pheomelanin synthesis in vitro.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0031-8655
pubmed:author
pubmed:issnType
Print
pubmed:volume
84
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
593-9
pubmed:meshHeading
pubmed:articleTitle
The "benzothiazine" chromophore of pheomelanins: a reassessment.
pubmed:affiliation
Department of Organic Chemistry and Biochemistry, University of Naples Federico II Complesso Universitario, Monte S. Angelo, Naples, Italy. alesnapo@unina.it
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't