Site-specific PEGylation of proteins by a Staudinger-phosphite reaction

Abstract

Current protocols in protein bioengineering allow the site-specific incorporation of chemical reporter moieties. Subsequently, these functional groups can be chemoselectively transformed to decorate proteins with charged and oversized functional units. Based on our recent report on the chemoselective reaction of azides with phosphites, we now apply the Staudinger-phosphite reaction to an efficient and metal-free PEGylation of an azide-containing protein with symmetrical phosphites. Thereby, two types of branched oligoethylene glycol scaffolds are generated, which deliver either a stable or light-cleavable protein-PEG conjugate. Furthermore, we demonstrate that the Staudinger-phosphite reaction is an efficient transformation in both aqueous media as well as in a highly crowded bacterial cell lysate.