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 $-fD\sim R^{-9/4}$ 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.

• Received 26 May 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.138101