  We study theoretically the mechanical failure of a simple model of double
stranded DNA under an applied shear. Starting from a more microscopic
Hamiltonian that describes a sheared DNA, we arrive at a nonlinear
generalization of a ladder model of shear unzipping proposed earlier by
deGennes [deGennes P. G. C. R. Acad. Sci., Ser. IV; Phys., Astrophys. 2001,
1505]. Using this model and a combination of analytical and numerical methods,
we study the DNA "unzipping" transition when the shearing force exceeds a
critical threshold at zero temperature. We also explore the effects of sequence
heterogeneity and finite temperature and discuss possible applications to
determine the strength of colloidal nanoparticle assemblies functionalized by
DNA.
