Departamento de Matemáticas y Mecánica, IIMAS-UNAM (Mexico)
Transport of polymers across channels is known as polymer translocation. To study translocation we have developed theoretical models for heteropoly- mers threading a rigid wall through a small pore. Coarse-grained models based only on steric interactions lead to computation of free energy, and the translocation time as the mean first-passage time from a Fokker-Planck equa- tion. We applied our models to polypeptides and analyzed the dependency of chain-sequence on translocation through the intrinsic tendency of monomers to participate in helical conformations and its energy penalty in a non-native conformation. Results show asymmetric umbrella-like free energy barriers for translocation, that have strong modulation by the energy penalty. The modulation allows to find conditions when variations in chain sequence are barely noticeable, in consequence, chain size becomes dominant leading to scaling for the translocation time, τ = ANξ with ξ =1.60–1.66, otherwise, chain-sequence may lead to translocation time jumps spanning several orders of magnitude.