ESTIMATION OF CALCIUM-BINDING CONSTANTS OF CASEIN PHOSPHOPEPTIDES BY CAPILLARY-ZONE-ELECTROPHORESIS

Measurement: of electrophoretic mobilities of bovine casein phosphopep tides (alpha s(1)-CN(59-79), alpha s(1)-CN(43-58), beta-CN(1-25), and beta-CN(33-48)) and their dephosphorylated analogues at different calc ium concentrations enabled the calculation of calcium-binding constant s in the range of pH 5-8. Binding constants showed a maximum at pH 7 a nd were in the range 0.1-0.5 mM(-1). The decrease at pH 8 might be att ributed to the presence of carbon dioxide, leading to competitive bind ing of calcium ions. Phosphorylated peptides exhibited higher binding constants than their dephosphorylated analogues. (C) 1998 Elsevier Sci ence B.V. All rights reserved.