Calmodulin-Separopore® 4B is used for affinity purification of calmodulin-binding proteins including calmodulin-regulated proteins in eukaryotic cells and recombinant proteins containing calmodulin-binding peptide fusion tag. Calmodulin binds proteins principally through their interactions with hydrophobic sites on its surface. These sites are exposed after a conformational change induced by the action of Ca2+ on separate Ca2+-binding site. The binding of enzymes may be enhanced if the enzyme substrate is present and enzyme substrate calmoldulin-Ca2+ complexes are particularly stable.