Folding Kinetics of Human Telomeric G Quadruplex (HTG) Sequence

G-Quadruplex (GQ) DNA sequences exhibit a novel secondary structure, where four tracts of guanines participate in Hoogsteen base pairing to make a stable structure. While much work has been done on these structures, their folding kinetics are still not completely understood. Here, we report on the conformation dynamics of the Human Telomeric G-Quadruplex sequence (HTG) monitored via F rester Resonance Energy Transfer (FRET), a technique which can monitor the nanoscale separation of two extrinsic fluorescent dye labels. Our data is consistent with the kinetic scheme of Gray et al., where the unfolded quadruplex passes through a long-lived intermediate on the way to the folded state. Preliminary kinetic data taken in various sucrose concentrations, a viscogen and molecular crowding agent, shows an appreciable effect. We seek to correlate and rationalize this dependence to understand GQ folding dynamics in the crowded and viscous environment of the cell.