Hydroxyt-Terminated Polyvinylpyrrolidone for the Modification of Polypeptides

Polyvinylpyrrolidone (PVP) oligomers with -OH terminal groups, obtained by radical polymerization using 2-mercaptoethanol as chain- transfer agent, were fractionated by gel chromatography to obtain a product with an approximate molecular weight of 1100. The hydroxyl function of such oligomer was activated with 4-nitrophenyl chloroformate to give an active car bonate derivative suitable for linking to peptide or protein amino groups in aqueous media buffered at mild alkaline pH. The linking of the PVP to the pro tein surface was accomplished without loss of enzymatic activity in the model enzyme ribonuclease. When the polymerization of PVP is carried out using 2- mercaptoacetic acid as chain-transfer agent, a much more heterogeneous prod uct was obtained. Also this, activated as succinimidyl ester, could also be bound to amine groups; however, this treatment performed on the model enzyme RNase caused inactivation.