Hydroxyl-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 carbonate 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 protein 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 product 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