Effect of ribose versus 2′-deoxyribose residue in guanosine 5′-monophosphates on formation of G-quartets stabilized by potassium and sodium cations

Raman spectroscopy was used to directly compare different abilities of monomeric ribo- and 2′-deoxyribo guanosine 5′-monophosphates to constitute G-quartets and their supramolecular self-assemblies stabilized by Na+ and K+ cations in pH-neutral or slightly basic aqueous solutions. Nucleotide concentration, stoichiometry and temperature was systematically varied to show that in the presence of Na+ cations, 5′-dGMP remains unordered under the conditions when 5′-rGMP already forms Na+-stabilized G-quartets and soluble ordered assemblies. On the contrary, in the presence of K+ ions both 5′-GMPs readily form self-stacking G-quartets, although self-association of 5′-rGMP is still greater than that of 5′-dGMP. These results are supported by 1H and 31P NMR spectroscopy. The cation-sensitive effect of ribose versus 2′-deoxyribose substitution on the formation of G-quartets and soluble aggregates from monomeric 5′-guanosine monophosphates under physiological pH could be essential for full understanding of different structural polymorphism of RNA and DNA quadruplexes.