Eupergit C as a carrier for high-performance liquid chromatographic-based immunopurification of antigens and antibodies

Calcium-modulated conformational affinity chromatography. Application to the purification of calmodulin and S100 proteins

The purification of proteins by affinity chromatography is based on their highly specific interaction with an immobilized ligand followed by elution under conditions where their affinity towards the ligand is markedly reduced. Thus, a high-degree purification by a single chromatographic step is achieved. However, when several proteins in the crude mixture share affinity to a common immobilized ligand, they may not be resolved by affinity chromatography and subsequent "real" chromatographic purification steps may be required. It is shown that by using properly selected gradient elution conditions, the affinities of the various proteins towards the immobilized ligand may be gradually modulated and their separation may be achieved. This is exemplified by the isolation and separation of a group of Ca(2+)-activated proteins, Calmodulin, S100a and S100b, from bovine brain extract, using a melittin-Eupergit C affinity column which is developed with Ca(2+)-chelator gradients. As expected, separation of the three proteins into individual peaks, eluted in order of increasing affinity to the matrix, was obtained. Sigmoid selectivity curves calculated from the elution volumes under different elution conditions for each of the proteins were obtained, illustrating the chromatographic behaviour of the gradient affinity separation system.

Factors affecting the specific activity of immobilized antibodies and their biologically active fragments

Factors affecting the specific activity of immobilized antibodies and their biologically active fragments were studied with goat anti-mouse and goat anti-human immunoglobulin G. Antibodies were immobilized on HW 65 polymeric support matrix activated with carbonyldiimidazole, hydrazide and iodoacetic acid. The most significant factors influencing the specific activity of stochastic coupling of antibodies are multi-site attachment, multiple orientations and steric hindrance imposed by crowding of antibody and the size of the antigen. In oriented immobilization the specific activity is affected only by steric hindrance. The specific activity of immunosorbents prepared by immobilization of F(ab') fragments can be improved to almost 100% by limiting the amount of protein immobilization and the size of the antigen. The present study shows the protocols for optimizing immobilized antibody performance.

Effect of polyethylene glycol on the non-specific adsorption of proteins to Eupergit C and agarose

Non-specific adsorption of serum proteins to Eupergit C (EC) and agarose during the process of immunoaffinity chromatography often leads to contamination of the specifically eluted antigens to be purified. This effect was studied by application of serum samples to a beta-mercaptoethanol-blocked EC (EC-beta ME) column followed by analysis of proteins eluted with various elution buffers. Inclusion of polyethylene glycol (PEG 400 or 1500) in the loading buffer reduced the non-specific adsorption of proteins to EC but had an adverse effect on agarose. Covalent attachment of amino-PEG to EC and to epoxy-activated Sepharose mimicked the effect of PEG in solution with EC and resulted in a marked reduction in non-specific adsorption of serum proteins. Inclusion of PEG in the loading buffer during immunopurification of a serum protein (immunoglobulin G) or seminal plasma protein (human decidua protein hDP71) resulted in a marked improvement in the purity of these proteins eluted from the respective columns by ammonium acetate (pH 10).