Differential biophysical behavior of human telomeric RNA and DNA quadruplex

Quadruplex forming potential has also been observed at the RNA level and has been associated with molecular function and recognition; however, biophysical characterization of these structures to understand their recognition properties still remains a subject of investigation. We employed CD and UV spectroscopy to understand the conformation and stability of a 24-mer human telomeric RNA quadruplex and compared it with that of the corresponding DNA analogue in 100 mM KCl containing solution. We observed that the RNA quadruplex adopts a parallel conformation and displays remarkably high thermal stabilities as compared to its DNA counterpart. Using the osmotic stress method, we determined the net release of 6.0+/-0.5 and 4.0+/-0.4 water molecules from the RNA and DNA quadruplex structure, respectively. Furthermore, UV titration experiments showed that both human telomeric RNA and DNA quadruplexes possess similar recognition abilities for TMPyP4 molecules. Our study provides a lead in extending the knowledge generated for the DNA quadruplex to the RNA level.