Catalytic peptide synthesis by trypsin modified with polystyrene in chloroform

Trypsin was modified with a hydrophobic synthetic polymer, polystyrene. The attachment was achieved by first coupling free amines in the trypsin with azo-bis(4-cyano-valeric acid) and then irradiating the product in the presence of styrene. Decomposition of the azo structure provided free radical initiation of styrene polymerization, with the trypsin thus becoming part of the end group for the polymer chain initiated. That the modified trypsin retained catalytic activity when dissolved in chloroform was demonstrated by using it to catalyze the formation of a peptide linkage between amino acids. The catalytic reaction was stereoselective.