Complexation and precipitation in polyampholyte solutions

We discuss multichain effects in polyampholyte solutions of finite concentration and find that the existing single-chain theories are limited to exponentially small concentrations, if the sample contains chains with net charges of both signs. We show that charged polyampholytes have a strong tendency to form neutral complexes and to precipitate. Stretched chains almost play no role in the ideal case of a neutral sample with nearly symmetric charge distribution. However, for a non-neutral sample, the free counterions accumulate in the supernatant together with charged, elongated chains and the behavior of the solution is dominated by ''impurities.''