Following G-quartet formation by UV-spectroscopy

Oligodeoxynucleotides,which include stretches of guanines form a well-known tetrameric structure, We show that the recording of reversible absorbance changes at 295 nm allows to precisely monitor intramolecular guanine (G)-quartet formation and dissociation. Accurate T-m and thermodynamic values could be easily extracted from the data, whereas classical recordings at 260 nm led to a much larger uncertainty and in extreme cases, to completely inaccurate measurements. This inverted denaturation profile,vas observed for all G-quartet-forming oligonucleotides studied so far. This technique is very useful in all cases where intramolecular or intermolecular quadruplex formation is suspected. (C) 1998 Federation of European Biochemical Societies.