In:
European Journal of Biochemistry, Wiley, Vol. 16, No. 3 ( 1970-11), p. 584-591
Abstract:
Cations of monohydropteridine radicals have been obtained in solution and investigated by electron spin resonance. The hyperfine pattern of these signals as well as that of previously described trihydropteridine radical cations has been computed to agreement with experiment. The first mentioned radicals are shown to have 5,8‐H 2 Pter + ‐structure, whereas the latter are 5,6,7,8‐H 4 Pter + . Substitutions in the pyrimidine part of the system (positions 1–4) do not affect the spin distribution essentially in any case. In monohydropteridine the unpaired electron is delocalized over the whole pyrazine part of the system (positions 5–8), whereas in trihydropteridines it is mainly confined to N(5) and possibly to the bridge carbons. The biochemical implications of pteridine radicals are discussed. While two‐electron oxidoreduction, implying 7,8‐dihydropteridine, is thermodynamically irreversible, one‐electron oxidoreduction appears to be intermediate in the systems Pter/5,8‐H 2 Pter on the one hand, and 6,7‐H 2 Pter/H 4 Pter on the other hand, thus permitting rapid electron transfer. Hence, it is reasonable to assume that trihydropteridine radicals might be of biological importance, though clearly not as the strongly acidic cations described here, but maybe in the stabilized form of metal complexes. In this context, existence, stability and eventual biological importance of the various dihydropteridine isomers is discussed.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1970.16.issue-3
DOI:
10.1111/j.1432-1033.1970.tb01121.x
Language:
English
Publisher:
Wiley
Publication Date:
1970
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
2172518-4
SSG:
12
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