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Comparison of (a) absorption and (b) fluorescence spectra of two ribosides of 1,N2-etheno-2-aminopurine (3 and 4), obtained chemically (3, dark green curves) and enzymatically 4, using E. coli PNP as a catalyst (bright green curves). Spectra measured in phosphate buffer, pH 7. Fluorescence excitation is at 290 nm.
