The Nelson group predicted the force dependence of the unzipping of double stranded DNA, and the Prentiss group probed that unzipping https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.93.078101 https://www.cell.com/fulltext/S0006-3495(05)73329-4. Pierre DeGennes suggested that double stranded DNA could be melted by applying a shear force, and that the required force increases linearly with the number of bases in the dsDNA when the dsDNA is short, but reaches an asymptotic value when the dsDNA Is longer. https://journals.aps.org/pre/abstract/10.1103/PhysRevE.78.011920
The Prentiss group extended deGennes’ theory to consider the melting of dsDNA by pulling on one single backbone, https://iopscience.iop.org/article/10.1088/0953-8984/22/41/414106 . The theory was then extended to model the structure of dsDNA bound to RecA family proteins.