Characteristics of beta-lactoglobulin binding to the all-trans-retinal moiety covalently immobilized on Celite

All-trans-retinal was covalently immobilized on Celite and investigated as a bioselective adsorption matrix for beta-lactoglobulin. Two types of Celite supports were compared, indicating the best performance with 100/120 mesh, type R648. The R648 matrix yielded a high concentration (9.2 mumol/ml) of the ligand when the derivative was produced, and the derivatized matrix exhibited the best retention of beta-lactoglobulin. Binding of beta-lactoglobulin to the immobilized trans-retinal matrix is biospecific, but the affinity is dependent on pH and ionic strength. alpha-Lactalbumin is not bound to this bioselective adsorbant, so its elution was not retarded or affected by pH or buffer concentration. Affinity for beta-lactoglobulin was optimal at pH 5.14; a dissociation constant of 2.7 microM was obtained in .1 M buffer solutions. At pH 7.0, the affinity decreased 44-fold, and, below pH 3.5, no binding occurred. The estimated loading capacity based on chromatographic data was approximately 14 g/L (.75 mumol/ml) of support.