Dynamic Melting Properties of Photoswitch-Modified DNA: Shearing versus Unzipping

摘要

We use dynamic force spectroscopy to study the melting properties of azobenzene-modified double stranded DNA (azo-dsDNA) in both the shearing and unzipping geometries. By fitting the rupture force vs loading rate data with a Friddle-Noy-De Yoreo model, we extract the location of the barrier (x(t)), the equilibrium force for the bond/transducer system (F-eq), and the dissociation rate of dsDNA (k(off)(0)). We find that the k(off)(0) of azo-dsDNA increases after UV illumination (36S nm) in both the shearing and unzipping geometries. Notably, we find that k(off)(0) of azo-dsDNA in the unzipping geometry is 5-7 orders of magnitude larger than that in the shearing geometry, a result that helps explain the dependence of k(off)(0) on the azobenzene photoswitch position during shearing experiments. We also extract the difference of free energy (Delta G(bu)) between binding and unbinding states of azo-dsDNA with F-eq and the system spring constant (k(c)). Our results provide important insights into the dynamic melting properties of azo-dsDNA and a new route for designing applications for reconfigurable sensors, stimulus-response materials, and nanoscale energy harvesting schemes based on photoswitch-modified biomolecules such as DNA.