Compression and stretching of a self-avoiding chain in cylindrical nanopores

Force-induced deformations of a self-avoiding chain confined inside a cylindrical cavity, with diameter D, are probed using molecular dynamics simulations, scaling analysis, and analytical calculations. We obtain and confirm a simple scaling relation -fD similar to R(-9/4) in the strong-compression regime, while for weak deformations, we find fD = -A(R/R(0)) + B(R/R(0))(-2), where A and B are constants, f the external force, and R the chain extension (with R(0) its unperturbed value). For a strong stretch, we present a universal, analytical force-extension relation. Our results can be used to analyze the behavior of biomolecules in confinement.