Derivatives of proteins. II. Coupling of α‐chymotrypsin to carboxyl‐containing polymers by use of N‐ethyl‐5‐phenylisoxazolium‐3′‐sulfonate

A method for covalently binding proteins to carboxyl‐containing polymers is described. N‐Ethyl‐5‐pheriylisoxazolium‐3′‐sulfonate is used to form active esters of the carboxyls, which then condense with amine groups on the protein to yield amides. Conjugates of α‐chymotrypsin with such polymers have been obtained, with nearly full retention of enzymatic activity in some preparations.