Purification of placental alkaline phosphatase by sulphate-mediated chromatography on Cibacron Blue 3G-A

Affinity chromatography and co-chromatography of bispecific monoclonal antibody immunoconjugates

Bispecific monoclonal antibodies (bsMAb) are unique macromolecules functioning as cross-linkers with two different predetermined binding specificities. A wide range of potential applications employing these probes can be envisioned in immunodiagnostics and immunotherapy. One of the major limitations for the use of bsMAbs produced by hybrid-hybridomas is the production of parental monospecific antibodies along with bsMAbs. Hence, the purification of desired bsMAb free from both parental mAbs and other possible promiscuous combinations is essential. Purification of antibodies is the single greatest obstacle in obtaining an immunoprobe with high specific activity. This review describes the affinity purification and affinity co-purification techniques for the separation of bsMAb as a pre-formed immune complex or as a pure species. The use of immobilized ligands is the basis of affinity chromatography. Affinity chromatography can be classified into three different categories depending on the properties of the immobilized ligand. The ligand-specific affinity chromatography is based on the extremely specific immobilized ligand, directed towards the protein or antibody of interest. Using a dual, sequential affinity chromatography, bsMAb can be purified from a mixture of bispecific and monospecific monoclonal antibodies with a ligand specific for each antibody. Thiophilic adsorption is a group-specific affinity method that can be successfully used to separate monospecific forms from bispecific species by salt gradient elution. Affinity co-chromatography offers a convenient one-step method for purification of bulk amounts of immunoconjugates for diagnostic applications by exploiting several dye-ligands known to bind certain enzymes. The same method could be potentially used for quality control and quality assurance purposes in industrial biotechnology.

Interactions of human alkaline phosphatase isoenzymes with triazine dyes using affinity partitioning, affinity chromatography and difference spectroscopy

Aqueous two-phase systems consisting of dextran, polyethylene glycol and dye-liganded polyethylene glycol were employed to investigate the affinity partitioning behaviour of isoenzymes of human alkaline phosphatase. Whereas in the system without a dye ligand the partition coefficients of the isoenzymes from human intestine and placenta were identical, the isoenzyme from human liver showed a significantly lower partition coefficient under the same conditions. After addition of dye-liganded polyethylene glycol two groups of dyes possessing substantial affinities to the isoenzymes were found. One, represented by Procion Yellow HE-3G, interacts specifically with the active centre of the isoenzymes. Differences in the affinity of the isoenzymes towards the individual dye ligands are caused only by the carbohydrate content, especially by the terminal sialic acid residues. The other group of dye ligands, represented by Procion Navy MX-RB, binds obviously in a more complex fashion involving other binding sites, which are only present in alkaline phosphatase of human liver. Procion Navy MX-RB was found to function as a suitable affinity ligand for the separation of human liver alkaline phosphatase from the other isoenzymes. Differences in the primary structure of two allelic forms of human placental alkaline phosphatase [(SS) and (F)] are not recognized in aqueous two-phase systems with or without dye-liganded polyethylene glycol.

Design and applications of biomimetic anthraquinone dyes. Purification of calf intestinal alkaline phosphatase with immobilised terminal ring analogues of C.I. reactive blue 2

A 330-fold one-step purification of alkaline phosphatase from a crude calf intestinal extract has been achieved using specific elution with inorganic phosphate (5 mM) from a purpose designed adsorbent comprising a terminal ring phosphonate analogue of C.I. Reactive Blue 2 coupled to Sepharose CL-6B-200. The resulting alkaline phosphatase preparation displayed a specific activity in excess of 1000 U/mg and was of equivalent purity to commercial "high purity" preparations as deduced by sodium dodecyl sulphate polyacrylamide gel electrophoresis and specific activity comparisons.