Surface Tension Kinetics of the Wild Type and Four Synthetic Stability Mutants of T4 Phage Lysozyme at the Air–Water Interface

✍ Scribed by Jun Wang; Joseph McGuire

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 156 KB
• Volume: 185
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.4619

✦ Synopsis

Surface tension kinetics exhibited by the wild type and selected stability mutants of T4 lysozyme at the air-water interface were monitored with DuNouy tensiometry. Mutant lysozymes were produced by substitution of the isoleucine at position 3 with cysteine, leucine, glycine, and tryptophan. Each substitution resulted in an altered structural stability quantified by a change in the free energy of unfolding. Surface pressure kinetics were compared to the kinetic model evolving from a simple model for protein adsorption. This model allowed for parallel, irreversible adsorption into two states directly from solution, where state 2 molecules were more tightly bound to the surface and occupied greater interfacial area than state 1 molecules. Moreover, the model allowed state 2 molecules to increase spreading pressure more than state 1 molecules occupying the same interfacial area. The model indicated that less stable variants of T4 lysozyme have a greater tendency to adsorb in state 2, and state 2 molecules increase spreading pressure more than state 1 molecules occupying the same interfacial area. While agreement between the model and experimental data was very good at low concentration, these results suggest that a more comprehensive two-state model should account for the influence of surface coverage on the adsorption rate constants.