Solvent Viscosity Tunes DNA Folding

In work with implications for future studies on DNA folding into structures called G-quadruplexes, Nicholas V. Hud and coworkers at Georgia Tech have found that solvent viscosity can tune the kinetics and pathway of G-quadruplex structural transitions (J. Am. Chem. Soc., DOI: 10.1021/ja303499m). Guanine-rich DNA sequences at chromosome ends, known as telomeres, can form G-quadruplexes­—structures that may play important roles in aging and cancer. Hud and coworkers observe that in a high-viscosity, low-water solvent telomeric DNA forms a roughly spherical G-quadruplex in about an hour. It then takes more than six months to further convert into a more planar G-quadruplex. But in a low-viscosity solvent, telomeric DNA folds into the same planar structure in less than two minutes. The findings highlight the need to consider solvent viscosity in studies of G-quadruplex formation in vitro and in vivo, could aid understanding of the way other nucleic acids fold, and could have applications in DNA-based nanotechnology, the researchers note.