Hydroxyapatite, Ca5(PO4)3(OH)2, is a form of calcium phosphate that is widely used in preparative biochemistry for the separation and purification of monoclonal antibodies and other proteins, nucleic acids, viruses, and other macromolecules. It is useful for preparative work in column or batch modes and for quantitative analysis of proteins or nucleic acids.
Its advantages include:
- Unique selectivity — separation on hydroxyapatite is not primarily dependent on molecular weight, molecular size, charge density, or isoelectric point. This makes hydroxyapatite chromatography a valuable complement to other separations techniques
- High capacity — surface area of about 50 m2/g
- Specificity — nonspecific adsorption of hydrophobic substances is minimized by the inorganic crystalline matrix of hydroxyapatite. Hydroxyapatite displays negligible adsorptive capacity for low molecular weight substances such as mononucleotides, salts, and amino acids
- Chemical and thermal stability — wide range of chemical compatibilities (aqueous and inorganic solvents), thermal stability (autoclavable), and pH tolerance (pH >5.5) permit the use of hydroxyapatite under conditions that optimize the binding of nucleic acids and proteins
All Bio-Rad hydroxyapatite is tested for separation of double-stranded DNA (dsDNA) from single-stranded DNA (ssDNA), albumin binding capacity, DNA binding capacity, and flow capacity. The test results for separation of dsDNA from ssDNA are printed for each batch on the packaging label.
Bio-Gel HTP hydroxyapatite has been dried by a unique process developed at Bio-Rad. It may be stored without refrigeration, and, when resuspended in buffer, it has the same properties as Bio-Gel HT hydroxyapatite; 1 gram hydrates to 2–3 milliliters.
DNA grade Bio-Gel HTP is a dry powder with a smaller particle size than HTP gel. This gel has an increased capacity and enhanced selectivity for dsDNA. Due to its small particle size, it is recommended for batch mode chromatography or for use with very short columns.
Bio-Gel HTP hydroxyapatite is chemically and thermally stable, is compatible with a wide range of aqueous and organic solvents, and can be sanitized in NaOH. It has a pH tolerance of >5.5 and is autoclavable.