Protein complexation with acrylic polyampholytes

The interaction of dilute mixtures of proteins and ABC triblock methacrylic polyampholytes at different values of pH was investigated turbidimetrically. The onset of interaction was manifested by large changes in turbidity at certain critical pHs which lie close to the isoelectric points of the two interacting components. Protein precipitation yields in protein-polyampholyte binary mixtures followed the corresponding turbidity profiles and varied from 10% to 90%. The synthetic polyampholytes self-aggregate around their isoelectric point. The kinetics of precipitation of one of the same polymer with soybean trypsin inhibitor were studied, with turbidity-based characteristic times (exponential fit) of 2–3 min. The kinetics of precipitation of the protein-polymer mixture are slower than that of pure polymer because a small, but steady, long-term increase in turbidity is observed in the former case. The pH-dependence of the turbidity of binary mixtures of one protein and one synthetic polyampholyte, as well as a tertiary mixture of two proteins and one polyampholyte, were measured 30 min after the pH adjustment. The observations in these experiments along with the measured protein precipitation yields in the binary mixtures and the polyampholyte self-aggregation can be used for polymer removal and recycling. The latter constitutes a significant advantage over the use of homopolyelectrolytes which cannot easily be recycled. © 1994 John Wiley & Sons, Inc.