Polymeric Reagents for Protein Modification

Abstract

Protein modification with polymeric reagents is carried out to extend in vivo circulation, to reduce antigenicity or to improve physical properties, such as solubility. We have developed polymeric reagents for such modifications. One group is based on polyproline. Polyproline exists in aqueous solution as a relatively rigid structure, polyproline II. Its single amino group allows derivatization to yield reagents for either amino groups or sulfhydryl groups on the protein. Development of various polyethylene glycol active esters allowed us to compare the reativities of those esters in aqueous buffers, since polyethylene glycol imparted water solubility to esters which are not normally water soluble. We investigated the influence on relative reactivity of polyethylene glycol esters by comparing leaving groups (i.e., the hydroxyl component) and by comparing relative electrophilicity of carbonyl moiety.