Estimation of calcium-binding constants of casein phosphopeptides by capillary zone electrophoresis

Measurement: of electrophoretic mobilities of bovine casein phosphopeptides (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 calcium concentrations enabled the calculation of calcium-binding constants in the range of pH 5-8. Binding constants showed a maximum at pH 7 and were in the range 0.1-0.5 mM(-1). The decrease at pH 8 might be attributed to the presence of carbon dioxide, leading to competitive binding of calcium ions. Phosphorylated peptides exhibited higher binding constants than their dephosphorylated analogues. (C) 1998 Elsevier Science B.V. All rights reserved.