Stabilization And Induction Of Oligonucleotide I-motif Structure Via Graphene Quantum Dots

Human telomeric DNA C-rich sequences may adopt i-motif structures. i-Motif structure was observed in or near the regulatory regions of more than40%of all genes, especially in the promoter region of oncogenes, such as VEGF, c-Myc and Rb promoter regions. Thus they might be attractive targets for gene-regulation process and for anti-cancer therapeutics, and it is thus essential to tune the structure of i-motif.We demonstrate in this work that i-motif structure can be stabilized by graphene quantum dots (GQDs) under acidic condition, and more importantly GQDs can promote the formation of the i-motif structure under alkaline or physiological condition. The stabilization and induction mechanism of GQDs are systematically studied by CD, fluorescence spectroscopy, and melting temperature. We found that the GQDs stabilize i-motif structure through the end-stacking to its bases at the loops, thus reducing its solvent-accessible area of the i-motif. At alkaline condition, the stack of GQDs on the i-motif structure shifts the balance between the i-motif and unfolded structure by stabilizing the i-motif structure, eventually promotes the formation of i-motif. The possibility of the fine tuning i-motif stability and inducing i-motif formation would make GQDs useful in gene regulation and oligonucleotide based therapeutics.