Additional file 2: Figure S3. ESI–MS experiment for guanine produced by 34mel. Figure S4. ESI–MS and MS/MS experiments for commercial guanine. Figure S5. 1H-NMR characterization of 34mel crystals. Figure S6. UV–vis spectra for commercial and 34mel guanine in acid solution. Additional data 1. Elemental analysis of crystals purified from 34mel.