Synchrotron-excited time-resolved fluorescence spectroscopy of adenosine, protonated adenosine and 6N,6N-dimethyladenosine in aqueous solution at room temperature.

The fluorescence behavior of adenosine in neutral solution has been studied by time-resolved spectroscopy using synchrotron excitation and time-correlated single photon counting, and by decay time measurements. Three emissions have been identified and correlated with three excitation spectra. The assignment of these transitions has been made by comparison with similar measurements on 6N,6N-dimethyladenosine (6DMA), and on adenosine in acid solution (ADO H+). It is proposed that two of the transitions of adenosine which correlate with 6DMA originate from coplanar and orthogonal rotational conformers of the amino group. The other transition, correlating with ADO H+ may originate either from the 3H-imino tautomer, or from a differently solvated rotational conformer.