All spectra were recorded on a Uvikon XL spectrophotometer in 10 mM lithium cacodylate buffer (pH 7.2) at 3 or 4 μM oligonucleotide strand (except when stated otherwise) supplemented with 100 mM KCl.
Thermal difference spectra (TDS) were obtained by taking the difference between the absorbance spectra of unfolded and folded oligonucleotides that were recorded at high (>90°C) and low (4°C) temperatures, respectively in buffer containing 100 mM KCl. TDS provide specific signatures of different DNA structural conformations, provided that the structure is not too heat stable (a number of G4 structures do not melt at high temperatures) (27 (link)).
Isothermal difference spectra (IDS) were obtained as described previously in (25 (link)) by taking the difference between the absorbance spectra from unfolded and folded oligonucleotides. These spectra were respectively recorded before and after potassium cation addition (100 mM KCl) at 20°C. IDS provide specific signatures of different DNA structural conformations.
UV melting experiments to determine melting temperatures (Tm) of G4 structures were performed as previously described (28 (link),29 ). G4 unfolding is typically associated with a decrease in absorbance at 295 nm, giving an inverted transition at this wavelength.
Thermal difference spectra (TDS) were obtained by taking the difference between the absorbance spectra of unfolded and folded oligonucleotides that were recorded at high (>90°C) and low (4°C) temperatures, respectively in buffer containing 100 mM KCl. TDS provide specific signatures of different DNA structural conformations, provided that the structure is not too heat stable (a number of G4 structures do not melt at high temperatures) (27 (link)).
Isothermal difference spectra (IDS) were obtained as described previously in (25 (link)) by taking the difference between the absorbance spectra from unfolded and folded oligonucleotides. These spectra were respectively recorded before and after potassium cation addition (100 mM KCl) at 20°C. IDS provide specific signatures of different DNA structural conformations.
UV melting experiments to determine melting temperatures (Tm) of G4 structures were performed as previously described (28 (link),29 ). G4 unfolding is typically associated with a decrease in absorbance at 295 nm, giving an inverted transition at this wavelength.
