Sequence and Temperature Dependence of the End-to-End Collision Dynamics of Single-Stranded DNA

Intramolecular collision dynamics play an essential role in biomolecular folding and function and, increasingly, in the performance of biomimetic technologies. To date, however, the quantitative studies of dynamics of single-stranded nucleic acids have been limited. Thus motivated, here we investigate the sequence composition, chain-length, viscosity, and temperature dependencies of the end-to-end collision dynamics of single-stranded DNAs. We find that both the absolute collision rate and the temperature dependencies of these dynamics are base-composition dependent, suggesting that base stacking interactions are a significant contributor. For example, whereas the end-to-end collision dynamics of poly-thymine exhibit simple, linear Arrhenius behavior, the behavior of longer poly-adenine constructs is more complicated. Specifically, 20- and 25-adenine constructs exhibit biphasic temperature dependencies, with their temperature dependences becoming effectively indistinguishable from that of poly-thymine above 335 K for 20-adenines and 328 K for 25-adenines. The differing Arrhenius behaviors of poly-thymine and poly-adenine and the chain-length dependence of the temperature at which poly-adenine crosses over to behave like poly-thymine can be explained by a barrier friction mechanism in which, at low temperatures, the energy barrier for the local rearrangement of poly-adenine becomes the dominant contributor to its end-to-end collision dynamics.