Lysozyme effect on ion transmission through an ultrafiltration membrane
Résumé
The present study deals with the use of ultrafiltration membranes as a separating device for the ion fraction bound to the protein and the free ion fraction in order to characterize ion/protein binding. The Ca/lysozyme example is presented. The positive charge of lysozyme modified ion distribution on both sides of the membrane and this gave erroneous results. Ion distribution was found to be a function of pH, ionic strength and lysozyme concentration. Ca2+ transmission was modified from 80% to 120% by pH acting on the positive charge of lysozyme. The action of pH in addition to that of increasing lysozyme concentration gave rise to very variable Ca2+ transmission, whereas an increase in ionic strength reduced these effects. Thus, these results highlighted the need for caution before carrying out ion/protein binding studies, for instance by increasing the ionic strength.