title: Effect of PEG end-group hydrophobicity on lysozyme interactions in solution characterized by light scattering.
abstract: We compare protein-protein and protein-polymer osmotic virial coefficients measured by static light scattering for aqueous solutions of lysozyme with low-molecular-weight, hydroxy-terminated (hPEG) and methyl-terminated (mPEG) poly(ethylene glycol) at two solution conditions: pH 7.0 and 0.01 M ionic strength, and pH 6.2 and 0.8 M ionic strength. We find that adding PEG to aqueous lysozyme solutions makes a net repulsive contribution to lysozyme-lysozyme interactions, independent of ionic strength and PEG end-group hydrophobicity. PEG end-group hydrophobicity has a profound effect on the magnitude of this contribution, however, at low ionic strength where mPEG-lysozyme attractive interactions become significant. The enhanced attractions promote mPEG-lysozyme preferential interactions at the expense of lysozyme self-interactions, which leads to lysozyme-lysozyme interactions that are more repulsive in the presence of mPEG. These preferential interactions also lead to the preferential exclusion of diffusable ions locally around the protein, which results in a pronounced ionic strength dependence of mPEG-mediated lysozyme-lysozyme interactions.
authors.affiliation: William G. Lowrie Department of Chemical and Biomolecular Engineering, Ohio State University, Columbus, Ohio 43210, United States.
authors.forename: M Hamsa
authors.initials: MH
authors.lastname: Priya
authors.forename: L R
authors.initials: LR
authors.lastname: Pratt
authors.forename: M E
authors.initials: ME
authors.lastname: Paulaitis
mesh_terms: D000818:Animals; D002645:Chickens; D008027:Light; D009113:Muramidase / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011485:Protein Binding; D012542:Scattering, Radiation; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet
chemical_list: D012996:Solutions; D011092:Polyethylene Glycols; D009113:Muramidase