Gradient and isocratic high-performance hydrophobic interaction chromatography of proteins on agarose columns

Hydrophobic interaction chromatography for isolation and purification of Equ.cl, the horse major allergen

Equ.cl, the horse (Equus caballus) major allergen, was identified in a partially purified extract obtained from a crude aqueous horse dander extract, by acetonic precipitation and a salting-out process. It was isolated and purified by size-exclusion chromatography followed by hydrophobic interaction chromatography. Equ.cl appeared as an almost pure protein in a fraction eluted at 1.2 M ammonium sulphate from a phenyl Superose column. It is a single peptide with a relative molecular mass of 20,000 and a pI of ca. 3.9.

Scale-up of recombinant protein purification by hydrophobic interaction chromatography

The scale-up of hydrophobic interaction chromatography is described. Human recombinant superoxide dismutase was used as a model. The scale-up was performed by keeping the height to diameter (H/D) ratio of the column constant. The success of scale-up was evaluated by reversed-phase high-performance liquid chromatography of the eluted material. The wrong H/D ratio causes decreased resolution.

Isolation and characterization of catalase from Penicillium chrysogenum

Catalase from a crude preparation of Penicillium chrysogenum was isolated in a single chromatographic step by immobilized metal ion affinity chromatography (IMAC) on Cu(II)-Chelating Sepharose Fast Flow. A chromatographically and electrophoretically homogeneous enzyme was obtained in 89% yield. IMAC was found to be superior to ion-exchange, hydrophobic interaction, size-exclusion and concanavalin A affinity chromatography. Analytical and preparative chromatography gave essentially the same chromatograms. Isoelectric point, molecular weight (by ultracentrifugation), amino acid composition, carbohydrate content and subunit organization were determined. The apparent Michaelis-Menten constant, KM, and the azide competitor constant, Ki, were calculated and found to be 59 microM and 6.1 microM, respectively.

New developments in protein isolation, purification, and characterization

The most significant advancements in techniques and methods for protein purification and analysis have been made in liquid chromatography and in electrophoresis. In the area of chromatography, adsorbents based on new affinity principles have been prepared. New packing materials have facilitated the rapid progress of high-performance techniques. A great many new techniques in the field of electrophoresis have emerged. On an analytical scale, electrophoretic methods in two dimensions or in capillaries are unsurpassed in resolution power. Development of techniques for protein transfer between different media is a prerequisite for a full exploitation of the new methods. Modern techniques for analysis of submicrogram quantities facilitate the separation, detection, and characterization of complex protein mixtures.

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.

Surface hydrophobicity and electrophoretic mobilities of staphylococcal exotoxins with special reference to toxic shock syndrome toxin-1

The surface hydrophobicities of eleven staphylococcal toxins were estimated and compared with those of standard proteins on an octyl agarose column by high-performance hydrophobic-interaction chromatography (HP-HIC). Staphylococcal enterotoxins (SE) D, C3, C2, C1 and B showed a low surface hydrophobicity whereas alpha-toxin and gamma-toxin had a moderate surface hydrophobicity. SEA, toxic shock syndrome toxin-1 (TSST-1) and staphylococcal epidermolytic toxin (SET) showed high surface hydrophobicity and delta-toxin was the most hydrophobic protein. The electrophoretic mobility of the toxins was determined by free zone electrophoresis (FZE). All toxins except SEC1 and one of the two SEA species showed negative charge at pH 8.6. Charge heterogeneity was observed in SEA, SEC1, SEC3 and TSST-1: SEA and SEC1 had two overlapping components, whereas SEC3 and TSST-1 were resolved into two distinct components. The mobilities of the two TSST-1 components were estimated at -2.12 x 10(-5) and -3.60 x 10(-5) cm2v-1s-1, respectively, at 10 degrees C, and both fractions were immunologically indistinguishable as tested by specific TSST-1 antibodies with ELISA. An asymmetric peak was obtained in hydrophobic-interaction chromatography of TSST-1 indicating heterogeneity.

Chromatography of proteins on hydrophobic interaction and ion-exchange chromatographic matrices: mobile phase contributions to selectivity

The effect of mobile phase pH on the retention characteristics of eleven proteins was examined in hydrophobic interaction chromatography (HIC) on a SynChropak propyl stationary phase. Selectivity was shown to change with eluent pH. The effect of the displacing salt on the separation of proteins on a weakly hydrophobic weak-anion-exchange chromatography (AEC) packing was examined. Some differences in selectivity were observed when sodium sulfate was used as the displacing salt, compared to that observed with sodium chloride in the eluent. It was demonstrated that these AEC packings exhibited both electrostatic and hydrophobic properties, depending upon the type and concentration of salt used in the mobile phase. The addition of 20% ethylene glycol to the mobile phase was shown to reduce the hydrophobic interactions. The application of weakly hydrophobic weak-cation-exchange packings to HIC of proteins was demonstrated. Elution of such columns with descending sodium sulfate gradients was found to provide a selectivity different from that observed with a propyl stationary phase. Manipulation of mobile phases was shown to provide useful selectivity as a result of the combination of electrostatic and hydrophobic contributions to the separation process.

Application of high-performance chromatographic and electrophoretic methods to the purification and characterization of glucose oxidase and catalase from Penicillium chrysogenum

The high resolving power of the preparative and analytical high-performance chromatographic and electrophoretic methods recently developed in this laboratory for the separation of biopolymers has been demonstrated by the purification and characterization of glucose oxidase and catalase from Penicillium chrysogenum. Crude glucose oxidase was purified to homogeneity in one step by high-performance hydrophobic-interaction chromatography (HIC) on a pentylagarose column. Crude catalase was purified by a combination of HIC and high-performance anion-exchange chromatography on 3-diethylamino-2-hydroxypropylagarose. The homogeneity of the enzymes was monitored by high-performance electrophoresis and free zone electrophoresis. The pI values of these two enzymes determined by isoelectric focusing in the high-performance electrophoresis apparatus were 4.2 and 6.5, respectively. Their molecular weights were determined by high-performance molecular sieve chromatography on an agarose column. Glucose oxidase has a molecular weight of 175,000 and probably consists of two identical subunits, as sodium dodecyl sulphate polyacrylamide gel electrophoresis gave a molecular weight of around 72,000. The molecular weight of catalase, which is probably composed of non-identical subunits, as indicated by sodium dodecyl sulphate electrophoresis, is around 320,000. Some other characteristics of these two enzymes were also investigated, e.g., electrophoretic mobility, pH stability and optimum pH.

Gradient and isocratic high-performance liquid chromatography of proteins on a new agarose-based anion exchanger

We describe a new, simple, and mild method for the preparation of anion-exchangers, based on the coupling of alkylamines to epoxy-activated agarose (prepared by the reaction of agarose with butanediol diglycidyl ether). Since a polar OH-group is formed when an epoxide reacts with an OH or NH2 group, the ion-exchanger did not show any hydrophobic interaction. This is important, since it may be impossible to desorb a protein from an ion exchanger having a hydrophobic character, because increasing the salt concentration of the eluent to decrease the electrostatic binding inevitably strengthens the hydrophobic interaction. By the method described, 3-diethylamino-2-hydroxy-propyl agarose (DEAHP-agarose) was prepared. High resolution of proteins was obtained by gradient elution at both high and low degrees of substitution. However, isocratic separations required a low degree of substitution, in accordance with a hypothesis previously put forward in connection with a theoretical and experimental study of the conditions for isocratic elution of macromolecules on amphiphilic gels. A study of the retention times of several proteins at different pH levels and buffer compositions indicated that different pH levels should be tested for maximal resolution and that, in many cases, the best resolution can be obtained if the DEAHP-agarose is operated in a buffer containing sodium acetate instead of sodium chloride. A quaternary amine agarose, 3-methyldiethylamino-2-hydroxy-propyl agarose (QAE-agarose), can be synthesized easily from DEAHP-agarose by alkylation with methyl iodide. The titration curves of DEAHP-agarose and QAE-agarose showed pK values around 9.5 and 11.3, respectively.