TI-CHA Hydroxyapatite for Chromatography is a form of calcium phosphate, a porous spherical substance formed by high temperature calcination, which is a pure inorganic chromatography medium specially designed for the purification of biomolecules. It can be bound to biomolecules by various mechanisms: 1) phosphate is negatively charged and can bind positively charged biomolecules by forming ionic bonds; 2) calcium ions can bind biomolecules with free carboxyl groups, imidazole rings, and other electron donors by forming metal-chelating bonds; and 3) hydroxyl groups on the hydroxyapatite can bond to biomolecules by forming hydrogen bonds with hydroxyl groups on the biomolecules.
Spherical hydroxyapatite calcined at lower temperatures has smaller pores and a relatively large specific surface area, known as type A hydroxyapatite, which has a higher binding capacity for smaller molecular weight biomolecules. Because the crystal structures formed at different temperatures are different, the binding specificity for biomolecules is significantly different.
