Tuning substrate selectivity of a cationic enzyme using cationic polymers.

Noncovalent interactions between an artificial molecular scaffold and a protein are interesting due to the possibility of reversible modulation of the activity of the protein. alpha-Chymotrypsin is a positively charged protein that has been shown to interact with negatively charged polymers. Here we show that positively charged polymers are also capable of electrostatically binding to this protein. The resulting experiments show that the ability of a polymer to bind a protein does not depend only on the pI of the protein. We also realized that the variations in charge density in the polymer backbone afford different selectivities of the enzyme toward charged substrates.