Аннотация:An attempt to stabilize guanine-glyoxal adduct by NaBH4 reduction was made. The reaction product was found to be 2-β-hydroxyethylamino-6-oxopurine, which proved stable under various conditions. The experimental conditions used for monomer reduction (pH 12.7, 30°, 2 h) can be applied for analysis of polymers. A label can be introduced into a modified guanine nucleus by means of NaB3H4.