In What Ways Do Synthetic Nucleotides and Natural Base Lesions Alter the Structural Stability of G-Quadruplex Nucleic Acids?

Figure 3

CD spectra of different GQ topologies and a series of thermal unfolding profiles. (a) shows the CD spectra of the antiparallel basket architecture of htel-21 GQ recorded in 100 mM Na⁺ solution and characterized by positive Cotton effects near 295 nm and 240 nm and a negative one around 260 nm (solid line), as well as the polymorphic form adopted by the same oligodeoxynucleotide in 100 mM K⁺, which is a mixture of K⁺-stabilized antiparallel and the hybrid forms, with the positive ellipticity near 290 nm, a strong shoulder around 270 nm, and a negative one close to 240 nm (broken line). (b) displays, for comparison, the CD spectra of the same K⁺-stabilized mixture of the htel-21 GQ (dotted line) and the mixture of just the hybrid forms with two positive peaks of close to equal heights at 290 and 260 nm (dashed line), all determined at low (50–100 μM) DNA strand concentrations, as well as the majority parallel forms adopted at/above 2 mM of the strands (solid line) (see references in [8]). (c) illustrates normalized thermal unfolding profiles of 8-oxoguanine containing htel-21 GQs [26].

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