Topological Dependence of ds-DNA Confined in Nanoslits

Topological constraints are important for the DNA condensation in confinement, such as chromosome in the cell and bacteriophage DNA packaging. We investigated the topological dependence of the size, shape and diffusivity of $\lambda $-DNA confined in a nanoslit with height $h$ = 780 nm (\textbf{$\approx $ }bulk radius of gyration of $\lambda $-DNA) to strong confinement ($h$ = 20 nm $<<$ persistence length $p)$ are systematically investigated. Shape asphericity of both linear and circular DNA increases with decreasing $h$, which indicate the DNA become more anisotropic. Furthermore, we observed the transition from de Gennes to Odijk scaling in the measured extension and diffusivity when $h$ = Kuhn length $L_{k}$. Interestingly, the diffusivity of circular DNA is larger than linear DNA in the blob regime, but they are nearly equal in slits with $h \quad <<$ $L_{k}$.