Linked Life Data

6265209

Source:http://linkedlifedata.com/resource/pubmed/id/6265209

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1981-9-15
pubmed:abstractText
The thermodynamically stable and, therefore, analytically most important alloxazine and isoalloxazine radical cations have been studied in detail by electron paramagnetic resonance (EPR) spectroscopy. Isotopic and chemical substitutions have been made as in earlier studies with the less stable neutral and anionic species. The experimental spectra have been calculated with the aid of a more sophisticated computer-simulation program than previously used. Excellent fits were obtained only when all of the following atoms were taken into account in the hyperfine coupling scheme: N-5 H, N-10 H or CH3, C-6 H, C-7 H, C-8 H or CH3 and C-9 H. An additional but small coupling constant was required for the fit. This latter coupling constant is assigned to the nitrogen atom(s) of the pyrimidine subnucleus of (iso)alloxazine radical cations. The EPR-active proton is attached to N-5 as we also found for the neutral flavosemiquinone. The alloxazine and isoalloxazine radical cations exhibit an identical hyperfine coupling scheme but differ especially in the pyrazine nucleus with respect to the spin density distribution. This suggests that the geometrical structure of the two kinds of radicals is somewhat different. The highest spin density is, however, located at N-5 of (iso)alloxazine as has been found for the other flavosemiquinone species. The hyperfine coupling constants are interpreted in terms of spin densities and comparison is made with the most recently available quantum chemical calculations. All monomeric flavosemiquinone species are compared with each other and their differences in the submolecular structure are discussed briefly.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:volume
116
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
17-25
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1981
pubmed:articleTitle
On the molecular and submolecular structure of the semiquinone cations of alloxazines and isoalloxazines as revealed by electron-paramagnetic-resonance spectroscopy.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't