The reversible immobilization of proteins on nylon activated through the formation of a substituted imidoester, and its unusual properties.

Alkylation of nylon produces nylon imidate, which is used for the covalent coupling of enzymes and other proteins and ligands. Nylon imidate is unusually stable when stored wet, with a half-life of about 60 days. Reaction with enzymes has an optimum about pH 7-8 and is extremely rapid, with about 60% of the reaction being complete in the first 10 min. The amidine formed in reaction with an amino group can be displaced by another nucleophile. In view of this finding that nylon amidine is capable of exchanging proteins, it is now concluded that nylon-tube reactors containing immobilized enzymes made by this method may not be used as extracorporeal shunts or as on-line monitors on patients, since the enzyme in the reactor may be released into the circulation by nucleophiles in the blood. This can lead to complications. The chemistry of this displacement reaction is discussed.