Separation of Proteins on Polar Bonded Phases by Hydrophobic Interaction Chromatography

Chromatography in the downstream processing of biotechnological products

Chromatography techniques are essential for the isolation and purification of most of the high value products of modern biotechnology. The economically sensible and technically satisfactory downstream processing of a therapeutic protein, usually involves a number of chromatographic steps. Its development and optimization require considerable knowledge of the various physico-chemical and engineering aspects of biochemical chromatography. This review addresses the various modes of chromatography and the design of chromatographic separation processes from a biotechnologist's point of view. Strategies for optimizing the structure of the downstream process are outlined and scaling up consideration are discussed. The importance of the different chromatographic methods in research and development is estimated in an analysis of protein purification schemes recently published in the literature. Finally, examples of the application of chromatographic procedures for process scale product purification in the biotechnological industry are given.

Binary and ternary salt gradients in hydrophobic-interaction chromatography of proteins

Hydrophobic-interaction chromatography of mixtures of acidic and basic proteins having a wide range of molecular weights and hydrophobic character was carried out by using binary and ternary salt gradients. Chaotropic and antichaotropic salts as well as organic salts were incorporated in the eluents. The stationary phase consisted of macroporous silica with surface-bound polyether moieties. At constant eluent surface tension, gradient elution with two or three aqueous salt solutions was found to be superior to single-salt gradients in modulating hydrophobic-interaction chromatography retention and selectivity. The effect was attributed to the competitive salt-specific binding to the protein molecule and/or the stationary phase surface. Chaotropic/antichaotropic salt gradient systems exhibited vastly different selectivities upon changing the nature and concentrations of salts in the eluents. In general, the retention of basic proteins increased while that of acidic proteins either decreased or remained unchanged with the use of chaotropic salts. At the same surface tension of the eluent, KSCN and KC1O4 yielded different selectivities. The addition of organic salts, such as tetrabutylammonium bromide was found to be suitable for the separation of proteins having a wide range of isoelectric points.

Evaluation of advanced silica packings for the separation of biopolymers by high-performance liquid chromatography. V. Performance of non-porous monodisperse 1.5-microns bonded silicas in the separation of proteins by hydrophobic-interaction chromatography

Non-porous monodisperse 1.5-microns silicas were allowed to react with (A) and (B) N-acetylaminopropyltriethoxysilane to generate bonded phases useful in high-performance hydrophobic-interaction chromatography (HIC). Differences in the selectivity were observed between the amide and the ether phase. Peak capacities between 10 and 30 were achieved for several proteins with the amide and ether phase packed into columns of 36 X 8 mm I.D. and elution of the proteins under chromatographic conditions in which the gradient volume, VG, was held constant by varying the gradient time between 20 and 2.5 min and the flow-rate between 0.5 and 4.0 ml/min. The S values derived from the dependences of log k' on the volume fraction of the low ionic strength buffer, phi b, were of the same magnitude as reported for porous HIC silicas and showed a dependence on the molecular weight of the protein. Using these HIC stationary phases based on non-porous 1.5-microns supports, fast separations (less than 5 min) could be carried out with high biological recoveries.