Site accessibility and the pH dependence of the saturation capacity of a highly cross-linked matrix. Immobilized metal affinity chromatography of bovine serum albumin on chelating Superose

Membrane-based techniques for the separation and purification of proteins: an overview

Membrane processes are increasingly reported for various applications in both upstream and downstream technology, such as microfiltration, ultrafiltration, emerging processes as membrane chromatography, high performance tangential flow filtration and electrophoretic membrane contactor. Membrane-based processes are playing critical role in the field of separation/purification of biotechnological products. Membranes became an integral part of biotechnology and improvements in membrane technology are now focused on high resolution of bioproduct. In bioseparation, applications of membrane technologies include protein production/purification, protein-virus separation. This manuscript provides an overview of recent developments and published literature in membrane technology, focusing on special characteristics of the membranes and membrane-based processes that are now used for the production and purification of proteins.

Effect of the matrix structure and concentration of polymer-immobilized Ni2+–iminodiacetic acid complexes on retention of IgG1

Terpolymer bead particles (100-350 microm in diameter) were prepared by suspension radical polymerization from methacrylate esters [2,3-epoxypropyl methacrylate (GMA), 2-(2-hydroxyethoxy)ethyl methacrylate (DEGMA) and ethylene dimethacrylate (EDMA)] and subsequently derivatized affording iminodiacetic acid (IDA) chelating sorbents. The sorbents differed in pore volumes (0-0.7 cm3/g) and specific surface areas (0.03-9.8 m2/g) of their matrices as well as in the amounts of immobilized Ni2+-IDA complexes (0.03-1.58 mmol/g). The binding of imidazole was studied by frontal chromatography to evaluate the accessibility of Ni2+-IDA complexes. It was found that an increase in the bonded imidazole content with increasing immobilized Ni2+-IDA concentration was strongly dependent on the matrix morphology. A higher pore volume of the matrix significantly improved the utilizability of Ni2+-IDA complexes for imidazole binding. The performance of the sorbents based on two porous matrices with immobilized Ni2+-IDA concentration (0.1-1.58 mmol/g) differing in pore size distributions was compared in immobilized metal affinity chromatography (IMAC) of monoclonal mouse immunoglobulin IgG1 specific against human choriogonadotropic hormone (GTH-spec IgG1). The results have shown that sorbents based on matrix with large pores (up to 20 microm in diameter) exhibited high protein binding capacities. The GTH-spec IgG1 (Mw=158,000) was eluted from all the sorbents in its native form as was confirmed by MALDI-TOF.

Purification of native dehydrin from Glycine Max cv., Pisum sativum, and Rosmarinum officinalis by affinity chromatography

An improved method for the purification of dehydrin from soy (glycine max) is described. Acidic extraction of soy whey was followed by a three step chromatographic process: capture on copper charged Chelating Sepharose Big Beads, intermediate hydrophobic interaction chromatography on Source 15 PHE, and a polishing step on blue Sepharose. The 32-kDa native soy dehydrin was purified to a purity of greater than 98.5% with an overall recovery of 63%. When compared to a previously published purification procedure, recovery, time requirements, and sample preparation steps were improved. The developed method is readily scaleable. Preliminary results show that the process can be used for dehydrins from rosemary (Rosmarinum officinalis) and pea (Pisum sativum).

Interactions of proteins with immobilized metal ions: a comparative analysis using various isotherm models

Immobilized metal ion affinity chromatography (IMAC) is now a widely accepted technique for the purification of natural and recombinant therapeutic products and is beginning to find industrial applications. The design, optimization, and scale-up of a chromatographic process using IMAC demands a thorough understanding to be developed regarding the fundamental factors governing the various interactions between immobilized metal ions and proteins. Consequently, there is an immediate need to find out a theory that is able to account for these interactions most efficiently in a qualitative as well as a quantitative manner. In view of this requirement, the interactions of several model proteins (lysozyme, ovalbumin, bovine serum albumin, conalbumin, and wheat germ agglutinin) with metal (Cu(II), Ni(II))-chelated IDA (iminodiacetate) and tris(2-aminoethyl)amine were investigated. The adsorption data were analyzed using four isotherm models, viz., the general affinity interaction theory/Langmuir model, the Freundlich model, the Temkin model, and the Langmuir-Freundlich model, and the sorption parameters were computed. Although the first three models were applicable to some protein-IMA-M(II) systems, the Langmuir-Freundlich model appeared to be the most efficient model for explaining the interactions of proteins with IMA-M(II) gels. Also, this model was able to explain cooperativity and binding heterogeneity in quantitative terms. It is envisaged that this analysis would be useful in developing an improved understanding of protein-immobilized metal ion interactions and providing guidelines for designing preparative-scale separations using IMAC.

Alkaline treatment of the cellulose fiber affecting membrane column behaviour for high-performance immunoaffinity chromatography

The original cellulose fibers and those treated by alkaline solution were both used to prepare the acrylic membranes. The two kinds of membranes were packed into the columns for high-performance immunoaffinity chromatography by the immobilization of protein A on them. It was observed that the alkaline treatment of the cellulose fiber decreased the pressure resistance of the membrane to the mobile phases and greatly increased the accessible volume to the proteins, but affected the adsorption capacity of human IgG on the protein A membrane columns less. There is little difference between those two kinds of membranes on the adsorption capacities of HIgG, which means that the alkaline treatment of the cellulose fiber only significantly changes the void volume inter-membrane, and the porosity and surface area of membrane less. Alkaline treatment of the cellulose fiber reduced the membrane-column efficiency significantly. Some typical examples for the immunoaffinity analysis of IgG from human and dog plasma on the protein A membrane columns are illustrated.