title: Interactions of proteins with immobilized metal ions: a comparative analysis using various isotherm models.
abstract: 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.
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi, 110 016, India.
authors.forename: S
authors.initials: S
authors.lastname: Sharma
authors.forename: G P
authors.initials: GP
authors.lastname: Agarwal
mesh_terms: D002412:Cations; D008670:Metals / Q000737:chemistry*; D008956:Models, Chemical; D011506:Proteins / Q000737:chemistry*
chemical_list: D002412:Cations; D008670:Metals; D011506:Proteins