| Abstract: | Total purine content, expressed as μmol/g, or as percentage RNA of a conventionally defined composition, is suggested as a convenient index of the amount of uric acid precursors in SCP. A simple but reproducible analytical procedure was based on the extraction of RNA and nucleotides from dried microbial cells with 1 N-perchloric acid at room temperature, followed by hydrolysis to free bases by heating the cell-free extract for 1 h at 100°C. After precipitation as the silver complexes, washing, and regeneration with HCI, purines (mainly adenine + guanine) were determined by spectrophotometry at 252 nm. If absorbance at 264.5 nm was measured as well, adenine and guanine could be determined separately. Results with dried yeast and with fungal mycelium were confirmed by cation-exchange chromatography, when purines were eluted from the column by citrate buffers (pH 3.0–5.0). |
