Competitive adsorption of bacteriophage T4 lysozyme stability variants at hydrophilic glass surfaces

The competitive adsorption behavior exhibited by the wild-type T4 lysozyme and two of its structural stability variants was studied by 125I radioisotope labeling. The mutant lysozymes were produced by substitution of the isoleucine residue at position 3 in the wild type with a tryptophan residue, resulting in a protein with lower structural stability, or with a cysteine residue, resulting in a protein with higher structural stability. Adsorption kinetics were recorded for binary protein mixtures in contact with a clean glass surface, in which one variant had been radiolabeled and the other had not. All pair permutations were tested. The kinetic data show that in instances in which exchange reactions between adsorbed protein and dissolved protein occur, they occur such that more stable variants are removed from the surface by less stable variants. The less stable proteins thus exhibited an advantage in competitive adsorption over the more stable proteins, in these tests.