Molecular charge effects on protein behavior at hydrophobic and hydrophilic solid surfaces

• Published in: Food hydrocolloids Vol. 10; no. 3; pp. 285 - 293
• Main Authors: Podhipleux, Nilobon, Krisdhasima, Viwat, McGuire, Joseph
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1996; Elsevier
• Subjects: adsorption; Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts; bacteriophages; Biological and medical sciences; electrostatic interactions; Food industries; food research; Fundamental and applied biological sciences. Psychology; hydrophilic polymers; hydrophobicity; interface; kinetics; lysozyme; proteins; surfaces; Enzyme; Hydrophobicity; Hydrophily; Proteins; Interface properties; Adsorption; Glycosidases; Hydrolases; Technological properties; Kinetics; O-Glycosidases; Lysozyme; Electrostatic charge
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/S0268-005X(96)80003-8

The adsorption kinetics exhibited by selected charge mutants of bacteriophage T4 lysozyme at silanized silica surfaces were monitored with in situ ellipsometry. Mutant lysozymes were produced by substitution of lysine with glutamic acid. Each substitution resulted in a decrease in the net charge of the protein by 2 units. The wild type lysozyme of net charge +9, and two mutants of net charge + 7 and +5 were obtained from Escherichia coli strain RR1. Adsorption kinetics recorded at hydrophilic and hydrophobic interfaces were compared to the kinetic behavior predicted by two simple models for protein adsorption. One allowed for reversible adsorption followed by conversion to an irreversibly adsorbed form. The second model allowed for irreversible adsorption into one of two states directly from solution. Both models suggested that proteins apparently adsorbed at the interfaces more tightly and occupied a greater interfacial area with substitution of lysine with glutamic acid. These effects were related to the location of the substitutions relative to other mobile, solvent-exposed charged residues of the protein, and not to net charge.