The interaction of mammalian interferons with immobilized cibacron blue F3GA: modulation of binding strength

Dye-ligand affinity systems

Dye-ligands have been considered as one of the important alternatives to natural counterparts for specific affinity chromatography. Dye-ligands are able to bind most types of proteins, in some cases in a remarkably specific manner. They are commercially available, inexpensive, and can easily be immobilized, especially on matrices bearing hydroxyl groups. Although dyes are all synthetic in nature, they are still classified as affinity ligands because they interact with the active sites of many proteins mimicking the structure of the substrates, cofactors, or binding agents for those proteins. A number of textile dyes, known as reactive dyes, have been used for protein purification. Most of these reactive dyes consist of a chromophore (either azo dyes, anthraquinone, or phathalocyanine), linked to a reactive group (often a mono- or dichlorotriazine ring). The interaction between the dye ligand and proteins can be by complex combination of electrostatic, hydrophobic, hydrogen bonding. Selection of the supporting matrix is the first important consideration in dye-affinity systems. There are several methods for immobilization of dye molecules onto the support matrix, in which usually several intermediate steps are followed. Both the adsorption and elution steps should carefully be optimized/designed for a successful separation. Dye-affinity systems in the form of spherical sorbents or as affinity membranes have been used in protein separation.

Purification of human placental trophoblast interferon by two-dimensional high performance liquid chromatography

Human placental trophoblast challenged with Sendai virus induced IFNs mainly of the beta-type (75%) and relatively low levels of the alpha-type (25%). A two-step high performance liquid chromatographic procedure ("two-dimensional HPLC") has been developed for the complete purification of the placental trophoblast interferon beta (tro-IFN-beta) from serum-containing culture supernatant. The method involved a combination of high performance liquid affinity chromatography (HPLAC) on Cibacron Blue 3GA immobilized on an activated pressure stable macroporous synthetic polymer, 2-hydroxyethyl methacrylate vinyl sulphone (HEMA-BIO 1000 VS), as the first dimension and reversed-phase high performance liquid chromatography (RP-HPLC) on Separon SGX C-18 as the second. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot experiments showed that the tro-IFN-beta was present as a 24 kDa protein. Densitometric scanning analysis of Coomassie-stained gel revealed the purity of the final preparation to be greater than 99%. The purified tro-IFN-beta had a specific activity of 1.03 x 10(8) IU/mg of protein and the overall recovery was 81% of the total IFN-beta activity in the crude preparation and 61% of the total IFN activity.

Elution of interferon beta from blue sepharose by poly(vinylpyrrolidone)

Interferon beta produced by a cell line (MRC-5) of human embryonic lung fibroblasts adsorbs to Blue Sepharose CL-6B and may be dissociated at neutral pH using a buffer containing poly(vinylpyrrolidone) and sodium chloride. Poly(vinylpyrrolidone) of Mr 2500 or of Mr 25 000 is equally efficient on a w/w basis. The effect of substituting volatile ammonium salts for the sodium chloride has been investigated. The benefits of the use of poly(vinylpyrrolidone) compared with the use of the commonly-used dissociating agent, 1,2-ethanediol, are discussed. It is concluded that interferon preparations eluted by poly(vinylpyrrolidone) from Blue Sepharose may be suitable for clinical use with minimal additional processing or formulation.

Application of dye-ligant chromatography to the isolation of alpha-1-proteinase inhibitor and alpha-1-acid glycoprotein

Various Cibacron blue F3G-A substituted Sephadex G-100 gels which differ in the density of the bound dye were investigated for their applicability in the affinity chromatography of human serum proteins. Protein adsorption was found to depend strongly on the density of the covalently attached dye and on the pH of the applied buffer. A high degree of dye substitution of the gel caused binding of most of the serum proteins. Only a small number of proteins were found to appear in the breakthrough fraction. On this basis a simple and relatively mild procedure for the isolation of homogeneous alpha-1-proteinase inhibitor and alpha-1-acid glycoprotein from human serum was developed. Isolation of alpha-1-acid glycoprotein succeeded in only a single step, whereas that of alpha-1-proteinase inhibitor required two additional steps: a prior ammonium sulphate precipitation and a chromatographic step on DEAE-cellulose at pH 6.5.

Purification of human lymphoblastoid cell-derived interferon-alpha by controlled-pore glass bead adsorption chromatography and molecular sieving

Human lymphoblastoid cell-derived interferon-alpha has been purified by a combination of chromatography on controlled-pore glass 350, gel filtration on Ultrogel AcA 54 and hydrophobic chromatography on Phenyl-Sepharose CL-4B. Specific activities of greater than 10(7) units/mg have been obtained. Controlled-Pore Glass has the advantages of accommodating large volumes of induced medium in an "in-line" process giving high recoveries of interferon and removing most of any contaminating DNA.

The interaction of Cibacron Blue F3GA with troponin and its subunits

Binding of troponin to Cibacron Blue F3GA-agarose column and its selective release from the gel in the presence of 0.5 M KCl provides the basis for a new purification method. The two-step procedure consists of isoelectric precipitation of tropomyosin and chromatography of the resultant crude troponin supernatant on Affi-Gel Blue column. Adsorption of troponin to the immobilized dye appears to occur through the troponin-T subunit. Troponin-I and troponin-C do not bind to the blue agarose column, whereas troponin-T binds to it very tightly. Binding of the dye to troponin-T prevents formation of troponin-T-troponin-C complex, but does not interfere with direct interaction of troponin-T with troponin-I. The activity of troponin in conferring calcium sensitivity on actomyosin ATPase is not affected by Cibacron Blue. Circular dichroism and difference absorption measurements of complexes of the blue dye with troponin and its subunits reveal the presence of a tight binding site on whole troponin and on troponin-T (KA greater than or equal to 10(6) M). The existence of weak binding sites for the dye on troponin and all of its subunits is deduced from difference absorption studies. Cibacron Blue appears to be a sensitive probe for subunit interactions in troponin.

The complete purification of human leucocyte interferon

Human leucocyte interferon (HuLeIF) has now for the first time been purified by a series of techniques involving precipitation, gel filtration, and affinity chromatography with Cu-chelate, blue dextran, and antibody. The two major species of HuLeIF were identified as two clearly separable and stainable proteins representing 85% of the biological activity with molecular weights of 18,400 and 20,180 daltons. Three more subspecies of HuLeIF were demonstrated with molecular weights of 19,500, 20,900 and 22,130 daltons, representing 15% of the biological activity. Specific activity of pure interferon is 2 x 10(9) interferon units/mg protein. Recovery was about 50%, and the purification factor exceeded 350,000.

Protein purification using immobilised triazine dyes

This review attempts to identify proteins which selectively interact with immobilised triazine dyes such as Cibacron blue F3GA and Procion red HE 3B. Different support matrices are compared by examining the capacities of these dyes for proteins. Various approaches to the immobilisation of triazine dyes are considered together with the use of spacers. Some theories of the mechanism of protein retardation by immobilised dyes are discussed. A number of methods are suggested for the measurement of dye concentrations and for the modification of the binding of proteins to dye columns. The variety of elution methods is compared with a view to optimizing purifications. The scope of applications is reviewed as well as the choice of dye. Some advantages of triazine dyes over other affinity ligands are given. It is concluded that although no satisfactory mechanism for the binding of triazine dyes to proteins has yet been proposed, these dyes possess considerable potential for protein purification, particularly when applied on the large scale.