4-PHENOXY-3,5-DINITROBENZOYLPOLYETHYLENEGLYCOL - REVERSIBLE ATTACHMENT OF CYSTEINE-CONTAINING POLYPEPTIDES TO POLYMERS IN AQUEOUS-SOLUTIONS

Polyethyleneglycol of molecular weight 6000 was treated with 4‐phenoxy‐3,5‐dinitrobenzoyl chloride in warm toluene. The product of this reaction is a white crystalline solid containing 0.1–0.2 mmol of labile phenoxy groups per gram of polymer derivative. In aqueous buffers of pH 7, the phenoxydinitrobenzoyl polymer reacts rapidly with side‐chain sulfhydryl groups of cysteine, but very slowly with other functional groups found in polypeptides, yielding peptide‐polymer compounds in which the peptide and polymer are linked by a thiol‐sensitive dinitrophenylene bridge. Both small synthetic peptides and the B‐chain of bovine insulin thus linked to polyethylene glycol are soluble in water and in some organic solvents. An arginine‐containing peptide bound to the polymer was hydrolyzed by trypsin at the arginyl bond, indicating that the linear polyethyleneglycol support does not restrict access of enzymes to bound peptides. Release of peptides from the polymer is rapidly accomplished by treatment with thiols at pH 7 in aqueous solutions. Copyright © 1979 John Wiley & Sons, Inc.