Conformations of freely jointed polyampholytes in external fields

We extend our previous treatment [J. Chem. Phys. 103, 5070 (1995)] of polyampholytes (PAs, polymers with positively and negatively charged monomers) in an external field E, by modeling the PAs through freely jointed chains. Former works, based on Rouse-type models are linear, and hence are limited to sufficiently small values of E. The freely jointed chain model allows to consider the PAs conformations for E arbitrary. We calculate the PAs end-to-end distance for several charge distributions along the chain, which may be either ordered or random. For small E we recover previous results; large E-values lead to a crossover to stretched chain configurations, which depend crucially on the distribution of charges along the chain. (C) 1996 American Institute of Physics.