FLUORESCENCE OF MATRIX-ISOLATED GUANINE AND 7-METHYLGUANINE

We have prepared argon and nitrogen matrices containing guanine and 7- methylguanine, and measured their absorption, fluorescence excitation and fluorescence emission spectra. The fluorescence excitation spectru m of guanine shows four well-resolved bands in the range from 170 to 2 90 nm; excitation at the wavelengths of each of these bands results in a fluorescence emission with maximum intensity near 350 nm and a sing le-exponential decay with a lifetime of about 10 ns. There are signifi cant differences between the fluorescent excitation and emission spect ra of guanine and of 7-methylguanine, suggesting that the fluorescence observed from the guanine sample does not arise from a minority tauto mer.