Figure 4.

Spectral changes observed during the enzymatic ribosylation of ~35 μM N²,3-etheno-O⁶-methylguanine (3) with E. coli PNP as a catalyst. (a): UV absorption; (b): Fluorescence spectra. Conditions: 40 mM HEPES buffer, pH 7.3, 0.5 mM ribose-1-phosphate, 25 °C. The final (red) curves are recorded after ca. 24 h of reaction. Fluorescence excitation was taken at 280 nm.