Reaction of hydrated electrons with guanine derivatives: tautomerism of intermediate species.
Here, we show that two tautomers are produced by the protonation of the guanine-electron adduct. The fate of electron adducts of a variety of substituted guanosines was investigated by radiolytic methods and addressed computationally by means of time-dependent DFT (TD-B3LYP/6-311G**//B1B95/6-31+G**) calculations. The reaction of e(aq-) with guanosine and 1-methylguanosine produces two transient species, whereas the reaction with N2-ethylguanosine and N2,N2-diethylguanosine produces only one. The two short-lived intermediates, which show a substantial difference in their UV-visible spectra, are recognized to be two purine tautomers (i.e., iminic 18 and aminic 19 forms). The tautomerization 18 --> 19 occurs with a rate constant of ca. 1.5 x 106 s(-1) , and theory suggests that it is a water-assisted process.
D'Angelantonio
Mila
M
ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy, and UniVersity of Oxford,Gray Cancer Institute, Mount Vernon Hospital, Northwood, Middlesex, HA6 2JR, UK.
Russo
Marialuisa
M
Kaloudis
Panagiotis
P
Mulazzani
Quinto G
QG
Wardman
Peter
P
Guerra
Maurizio
M
Chatgilialoglu
Chryssostomos
C
D003198:Computer Simulation; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D008956:Models, Chemical; D013237:Stereoisomerism; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D005609:Free Radicals; D014867:Water; D006147:Guanine