Polyethylene glycol interferes with protein molecular weight determinations by gel filtration.

Gel filtration studies on Sephadex G-75 demonstrate markedly increased elution volumes for proteins chromatographed with polyethylene glycol. As little as 5% (w/v) polyethylene glycol in the applied protein sample can reduce apparent molecular weight estimates by gel filtration as much as 55%. Furthermore, gel filtration columns equilibrated with polyethylene glycol are not size-separating columns. Consequently, caution must be exercised when performing and interpreting gel filtration studies of proteins previously treated or precipitated with polyethylene glycol.