High-performance metal chelate interaction chromatography of proteins with silica-bound ethylenediamine-N,N′-diacetic acid

Chromatographic Behaviors of Proteins on Cation-Exchange Column

A weak cation-exchanger (XIDACE-WCX) has been synthesized by the indirect method. The chromatographic characteristics of the synthesized packing was studied in detail. The standard protein mixture and lysozyme from egg white were separated with the prepared chromatographic column. The chromatographic thermodynamics of proteins was studied in a wide temperature range. Thermodynamic parameters standard enthalpy change (deltaH0) and standard entropy change (deltaS0) and compensation temperature (beta) at protein denaturation were determined in the chromatographic system. By using obtained deltaS0, the conformational change of proteins was judged in the chromatographic process. The linear relationship between deltaH0 and deltaS0 can be used to identify the identity of the protein retention mechanism in the weak cation-exchange chromatography. The interaction between weak cation-exchanger and metal ions was investigated. Several metal chelate columns were prepared. The effects of introducing metal ion into the naked column on protein retention and the retention mechanism of proteins in the metal chalet affinity chromatography were discussed.

Contributions of commercial sorbents to the selectivity in immobilized metal affinity chromatography with Cu(II)

Immobilized copper(II) affinity chromatography [Cu(II)-immobilized metal affinity chromatography (IMAC)] has been used in proteomics to simplify sample mixtures by selecting histidine-containing peptides from proteolytic digests. This paper examines the specificity of four different support materials with an iminodiacetic acid (IDA) stationary phase in the selection of only histidine-containing peptides in the single step capture-release mode. Three of the sorbents examined were commercially available: HiTrap Chelating HP (agarose), TSK Chelate-5PW, and Poros 20MC. IDA was also immobilized on CIM discs (monolithic glycidylmethacrylate-ethylene dimethacrylate). Tryptic digests of transferrin and beta-galactosidase were used as model samples to evaluate these sorbents. It was found that among the examined matrices, the TSK Chelate-5PW sorbent bound histidine-containing peptides the strongest, while Poros matrix was found to have a high degree of non-specific bindings. Agarose-based columns showed relatively high selectivity and specificity.

Improvement of downstream processing of recombinant proteins by means of genetic engineering methods

The rapid advancement of genetic engineering has allowed to produce an impressive number of proteins on a scale which would not have been achieved by classical biotechnology. At the beginning of this development research was focussed on elucidating the mechanisms of protein overexpression. The appearance of inclusion bodies may illustrate the success. In the meantime, genetic engineering is not only expected to achieve overexpression, but to improve the whole process of protein production. For downstream processing of recombinant proteins, the synthesis of fusion proteins is of primary importance. Fusion with certain proteins or peptides may protect the target protein from proteolytic degradation and may alter its solubility. Intracellular proteins may be translocated by means of fusions with signal peptides. Affinity tags as fusion complements may render protein separation and purification highly selective. These methods as well as similar ones for improving the downstream processing of proteins will be discussed on the basis of recent literature.