Graduation date: 1995

The adsorption kinetics exhibited by selected charge mutants of T4 lysozyme at silanized silica surfaces were monitored with in situ ellipsometry. Mutant lysozymes were produced by substitution of lysine (Lys) with glutamic acid (Glu). 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 E. 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 was a three-rate-constant model allowing for reversible adsorption followed by conversion to an irreversibly adsorbed form, and was analyzed under three different conditions. The first condition allowed the adsorption rate (k₁) and the desorption rate (k₋₁) to be variable while the surface-induced conversion rate (s₁) was assumed constant. The second condition assumed k₁ and k₋₁ constant instead of S₁, and the third allowed all kinetic rate constants to be variable. The second model allowed for irreversible adsorption into one of two states directly from solution. Both models suggested that substitution of Lys with Glu in the backbone of T4 lysozyme facilitates the adsorption of the protein at these interfaces. Proteins apparently adsorbed at the interfaces more tightly and occupied a greater interfacial area with substitution of Lys with Glu, and these effects were related to the location of the substitutions relative to other charged residues of the protein, and not to net charge. / Graduation date: 1995

Graduation date: 1999

Graduation date: 1998

Graduation date: 1997