Ring opening of the cyclobutane in a thymine dimer radical anion.
The reactions of hydrated electrons (e(aq) (-)) with thymine dimer 2 and thymidine have been investigated by radiolytic methods coupled with product studies, and addressed computationally by means of BB1K-HMDFT calculations. Pulse radiolysis revealed that one-electron reduction of the thymine dimer 2 affords the radical anion of thymidine (5) with t(1/2)<35 ns. Indeed, the theoretical study suggests that radical anion 3, in which the spin density and charge distribution are located in both thymine rings, undergoes a fast partially ionic splitting of the cyclobutane with a half-life of a few ps. This model fits with the in vivo observation of thymine dimer repair in DNA by photolyase. gamma-Radiolysis of thymine dimer 2 demonstrates that the one-electron reduction and the subsequent cleavage of the cyclobutane ring does not proceed by means of a radical chain mechanism, that is, in this model reaction the T(-)* is unable to transfer an electron to the thymine dimer 2.
Chatgilialoglu
Chryssostomos
C
ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy. chrys@isof.cnr.it
Guerra
Maurizio
M
Kaloudis
Panagiotis
P
Houée-Lévin
Chantal
C
Marignier
Jean-Louis
JL
Swaminathan
Vijay N
VN
Carell
Thomas
T
D000838:Anions / Q000737:chemistry; D003503:Cyclobutanes / Q000138:chemical synthesis* / Q000737:chemistry / Q000528:radiation effects; D019281:Dimerization; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D005720:Gamma Rays; D008956:Models, Chemical; D008968:Molecular Conformation; D011675:Pulse Radiolysis; D011740:Pyrimidine Dimers / Q000737:chemistry* / Q000528:radiation effects; D013237:Stereoisomerism; D013936:Thymidine / Q000737:chemistry* / Q000528:radiation effects; D013941:Thymine / Q000737:chemistry* / Q000528:radiation effects
D000838:Anions; D003503:Cyclobutanes; D005609:Free Radicals; D011740:Pyrimidine Dimers; D013941:Thymine; D013936:Thymidine