Equilibrium properties of polyampholytes in electric fields

An analytically tractable model for the description of a charged polymer chain (polyampholyte) in an external electric field is presented. The chain is comprised of mass points and their connectivity is taken into account by harmonic constraints. In particular the finite extensibility of a chain is captured by our approach. Equilibrium properties for chains of various charge distributions are calculated, especially for intermediate and strong electric fields. Particularly, chains of alternating positive and negative charges are considered within a discrete chain model. For intermediate electric fields such chains exhibit stretched configurations, whereas for strong electric fields a collapse or stretching occurs depending on the number of mass points. In addition a continuous chain with random charge density is considered. Our investigations demonstrate that the equilibrium properties of polyampholytes in strong electric fields decisively depend on the charge distribution along the chain. (C) 1997 American Institute of Physics.