The human telomere has a G-rich strand possessing 5'-TTAGGG-3' repeats and the complementary C-rich strand possessing 5'-CCCTAA-3' repeats. Previous studies from our lab have demonstrated that (TTAGGG)4 forms a unimolecular G-quadruplex in the presence of K+which undergoes a thermally induced transition from the folded structure to a single stranded structure via a three state mechanism. The complementary strand, (CCCTAA)4, can also undergo a transition from a single stranded structure to a unimolecular i-motif upon lowering the pH from 7.0 to 5.0. We have been investigating the effects of sequence context and environment on the conformations and stabilities of synthetic DNA oligomers related to these sequences. To this end, spectroscopic and calorimetric studies on sequences (XXXGGG)4 and (CCCXXX)4, where X = A and/or T, were carried out to evaluate the influence of the XXXloops of the G-quadruplex or i-motif on their conformational properties. In addition, we have been investigating the influence of unpaired bases at the 5' and/or 3' termini of the G-quadruplex on its stability. Our results indicate that the conformational properties of G-quadruplexes and i-motifs are exquisitely linked to sequence context and environment. These results will be discussed in terms of the role of base stacking in the conformation and stability of these unusual DNA structures.

G-Quadruplexes and <i>?i</i>-motifs: Sequence context and environment influence conformation and stability

248th National Meeting (2014)

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G-Quadruplexes and ?i-motifs: Sequence context and environment influence conformation and stability