Branched Polyethylene Glycol for Protein Precipitation

Abstract

The use of linear polyethylene glycol (PEG) for protein precipitation raises the issues of high viscosity and limited selectivity. This project was aimed at alleviating the former problem through PEG branching. Novel star-branched PEG precipitants were synthesized and screened before selecting 3-arm star as the model branched structure. Further precipitation experiments elucidated the trade-off between viscosity and precipitation efficiency when PEG was branched. Even so, higher concentrations of branched PEGs reduced viscosity without adversely affecting the precipitation outcome, relative to linear versions of equivalent molecular weights. Drawing from empirical observations pointing to the central role of hydrodynamic radius, a generalized scientific model was developed. This led to a simple correlation that predicts the efficiency of general-shaped PEG precipitants as well as the effects of PEG branching, protein size, and environmental condition.