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

Investigation of Thermodynamic, Kinetic, and Isothermal Parameters for the Selective Adsorption of Bisphenol A

Herein, a novel imprinted solid-phase extraction cartridge was fabricated to investigate the kinetic, thermodynamic, and isothermal parameters for the selective adsorption of Bisphenol A (BPA). The imprinted polymeric cartridges (BMC) for the BPA adsorption were fabricated in the presence of a template and functional monomer using the in situ polymerization technique. To prove the efficiency and selectivity of BMC, the nonimprinted polymeric cartridges (BNC) and the empty polymeric cartridges (EC) were also fabricated with and without functional monomer using the same manner for the preparation of BMC. The characterization of cartridges was performed by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, and swelling tests. BPA removal studies were performed by analyzing some parameters such as temperature, BPA concentration, flow rate, salt type, and concentration. The highest capacity was determined as 103.2 mg BPA/g polymer for a 0.75 mL/min flow rate of 0.75 M (NH₄)₂SO₄ containing 200 mg/L BPA solution at 50 °C. NaOH (1.0 M) was used as a desorption agent. The reusability performance was examined by performing 10 consecutive cycles. The solid-phase extraction (SPE) performance was also checked to determine the enrichment and extraction recovery factors for tap water and synthetic wastewater samples. Temkin, Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were applied to BPA adsorption data examining the adsorption mechanism, surface properties, and adsorption degree. The most suitable isotherm model for BPA adsorption was determined as the Langmuir isotherm model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were investigated to reveal the thermodynamics of adsorption. Adsorption thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated using the thermodynamic equilibrium constant (thermodynamic equilibrium constant, K°) values that change with temperature. It was determined that BPA adsorption was spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) and entropy increased (ΔS° > 0) at the temperatures studied in the BPA adsorption process. The rate control step in the adsorption process was examined by applying pseudo-first-order and pseudo-second-order kinetic models to the adsorption data for the investigations of BPA adsorption kinetics, and the pseudo-second-order kinetic model was found to be more suitable for describing BPA adsorption kinetics. In examining the selectivity of cartridges, structural analogues of hydroquinone, phenol, β-estradiol, and 8-hydroxyquinoline were tested.

An Experimental and Modeling Combined Approach in Preparative Hydrophobic Interaction Chromatography

Chromatography is a technique widely used in the purification of biopharmaceuticals, and generally consists of several chromatographic steps. In this work, Hydrophobic Interaction Chromatography (HIC) is investigated as a polishing step for the purification of therapeutic proteins. Adsorption mechanisms in hydrophobic interaction chromatography are still not completely clear and a limited amount of published data is available. In addition to new data on adsorption isotherms for some proteins (obtained both by high-throughput and frontal analysis method), and a comparison of different models proposed in the literature, two different approaches are compared in this work to investigate HIC. The predictive approach exploits an in-house code that simulates the behavior of the component in the column using the model parameters found from the fitting of experimental data. The estimation approach, on the other hand, exploits commercial software in which the model parameters are found by the fitting of a few experimental chromatograms. The two approaches are validated on some bind-elute runs: the predictive approach is very informative, but the experimental effort needed is high; the estimation approach is more effective, but the knowledge gained is lower. The second approach is also applied to an in-development industrial purification process and successfully resulted in predicting the behavior of the system, allowing for optimization with a reduction in the time and amount of sample needed.

Practical method development for the separation of monoclonal antibodies and antibody-drug-conjugate species in hydrophobic interaction chromatography, part 1: optimization of the mobile phase

The goal of this work is to provide some recommendations for method development in HIC using monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) as model drug candidates. The effects of gradient steepness, mobile phase pH, salt concentration and type, as well as organic modifier were evaluated for tuning selectivity and retention in HIC. Except the nature of the stationary phase, which was not discussed in this study, the most important parameter for modifying selectivity was the gradient steepness. The addition of organic solvent (up to 15% isopropanol) in the mobile phase was also found to be useful for mAbs analysis, since it could provide some changes in elution order, in some cases. On the contrary, isopropanol was not beneficial with ADCs, since the most hydrophobic DAR species (DAR6 and DAR8) cannot be eluted from the stationary phase under these conditions. This study also illustrates the possibility to perform HIC method development using optimization software, such as Drylab. The optimum conditions suggested by the software were tested using therapeutic mAbs and commercial cysteine linked ADC (brentuximab-vedotin) and the average retention time errors between predicted and experimental retention times were ∼ 1%.

Molecularly imprinted cryogel cartridges for the specific filtration and rapid separation of interferon alpha

Molecularly imprinted cryogel-based specific filtration cartridges for highly selective, repeatable and fast interferon α-2b separation even if under competitive conditions.

Adsorption induced enzyme denaturation: the role of polymer hydrophobicity in adsorption and denaturation of alpha-chymotrypsin on allyl glycidyl ether (AGE)-ethylene glycol dimethacrylate (EGDM) copolymers

Effects of changes in hydrophobicity of polymeric support on structure and activity of alpha-chymotrypsin (E.C. 3.4.21.1) have been studied with copolymers of allyl glycidyl ether (AGE) and ethylene glycol dimethacrylate (EGDM) with increasing molar ratio of EGDM to AGE (cross-link density 0.05 to 1.5). The enzyme is readily adsorbed from aqueous buffer at room temperature following Langmuir adsorption isotherms in unexpectedly large amounts (25% w/w). Relative hydrophobicity of the copolymers has been assessed by studying adsorption of naphthalene and Fmoc-methionine by the series of copolymers from aqueous solutions. Polymer hydrophobicity appears to increase linearly on increasing cross-link density from 0.05 to 0.25. Further increase in cross-link density causes a decrease in naphthalene binding but has little effect on binding of Fmoc-Met. Binding of alpha-chymotrypsin to these copolymers follow the trend for Fmoc-methionine binding, rather than naphthalene binding, indicating involvement of polar interactions along with hydrophobic interactions during binding of protein to the polymer. The adsorbed enzyme undergoes extensive denaturation (ca. 80%) with loss of both tertiary and secondary structure on contact with the copolymers as revealed by fluorescence, CD and Raman spectra of the adsorbed protein. Comparison of enzyme adsorption behavior with Eupergit C, macroporous Amberlite XAD-2, and XAD-7 suggests that polar interactions of the EGDM ester functional groups with the protein play a significant role in enzyme denaturation.

Methods of calculating protein hydrophobicity and their application in developing correlations to predict hydrophobic interaction chromatography retention

Hydrophobic interaction chromatography (HIC) is a key technique for protein separation and purification. Different methodologies to estimate the hydrophobicity of a protein are reviewed, which have been related to the chromatographic behavior of proteins in HIC. These methodologies consider either knowledge of the three-dimensional structure or the amino acid composition of proteins. Despite some restrictions; they have proven to be useful in predicting protein retention time in HIC.

Comparison of standard and new generation hydrophobic interaction chromatography resins in the monoclonal antibody purification process

Recent efforts to improve hydrophobic interaction chromatography (HIC) for use in monoclonal antibody (mAb) purification have focused on two approaches: optimization of resin pore size to facilitate mAb mass transport, and use of novel hydrophobic charge induction (HCIC) mixed mode ligands that allow capture of mAbs under low salt conditions. We evaluated standard HIC and new generation HIC and HIC-related chromatography resins for mAb purification process efficiency and product quality both as isolated chromatography steps and in purification process trains. We find that HIC resins with optimized pore size have significantly improved binding capacity which can increase HIC purification unit operation efficiency. The HCIC Mercapto-Ethyl-Pyridine (MEP) resin, which shows a different salt impact trend and impurity resolution pattern from standard HIC resin, can not only capture mAb from crude CHO fermentation supernatant but also substantially enhance mAb purification process flow efficiency when serving as a polishing role.

Use of magnetic poly(glycidyl methacrylate) monosize beads for the purification of lysozyme in batch system

The hydrophobic affinity ligand L-tryptophan immobilized magnetic poly(glycidyl methacrylate) [m-poly(GMA)] beads in monosize form (1.6 microm in diameter) were used for the affinity purification of lysozyme from chicken egg white. The m-poly(GMA) beads were prepared by dispersion polymerization in the presence of Fe3O4 nano-powder. The epoxy groups of the m-poly(GMA) beads were converted into amino groups with 1,6 diaminohexane (i.e., spacer arm). l-tryptophan was then covalently immobilized on spacer arm attached m-poly(GMA) beads. Elemental analysis of immobilised L-tryptophan for nitrogen was estimated as 42.5 micromol/g polymer. Adsorption studies were performed under different conditions in a batch system (i.e., medium pH, protein concentration and temperature). Maximum lysozyme adsorption amount of m-poly(GMA) and m-poly(GMA)-L-tryptophan beads were 1.78 and 259.6 mg/g, respectively. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium adsorption capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. It was observed that after 10 adsorption-elution cycle, m-poly(GMA)-L-tryptophan beads can be used without significant loss in lysozyme adsorption capacity. Purification of lysozyme from egg white was also investigated. Purification of lysozyme was monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. It was found to be successful in achieving purification of lysozyme in a high yield of 76% with a purification fold of 71 in a single step. The specific activity of the eluted lysozyme (62,580 U/mg) was higher than that obtained with a commercially available pure lysozyme (Sigma (60,000 U/mg).

Optimal operation conditions for protein separation in hydrophobic interaction chromatography

Protein retention in hydrophobic interaction chromatography is determined by protein physicochemical properties and by system characteristics. In this paper we present an attempt to determine the optimal operation conditions that would allow the separation of binary protein mixtures. The statistically significant system variables were determined, and then empirical models were obtained which explained more than 92% of variability in dimensionless retention time based on salt properties, ionic strength of the initial eluent and substitution degree of the resin. These variables were optimized in order to achieve the maximum retention time difference between two proteins in a mixture. The optimum operation conditions as predicted by the models were tested experimentally, showing a good agreement with predicted separation. We concluded that it would be possible to determine the system conditions that allow the maximum separation of two proteins based on the main system properties. The methodology proposed here presents potential to be applied to partially characterized systems, however, it could be improved if protein's properties were included explicitly in the models.

Current insights on protein behaviour in hydrophobic interaction chromatography

This paper gives a summary of different aspects for predicting protein behaviour in hydrophobic interaction chromatography (HIC). First, a brief description of HIC, hydrophobic interactions, amino acid and protein hydrophobicity is presented. After that, several factors affecting protein chromatographic behaviour in HIC are described. Finally, different approaches for predicting protein retention time in HIC are shown. Using all this information, it could be possible to carry out computational experiments by varying the different operating conditions for the purification of a target protein; and then selecting the best conditions in silico and designing a rational protein purification process involving an HIC step.

Monosize poly(glycidyl methacrylate) beads for dye-affinity purification of lysozyme

Cibacron Blue F3GA was covalently attached onto monosize poly(glycidyl methacrylate) [poly(GMA)] beads for purification of lysozyme from chicken egg white. Monosize poly(GMA) beads, 1.6 microm in diameter, were produced by a dispersion polymerization technique. The content of epoxy groups on the surface of the poly(GMA) sample determined by the HCl-pyridine method (3.8 mmol/g). Cibacron Blue F3GA loading was 1.73 mmol/g. The monosize beads were characterized by elemental analysis, FTIR and SEM. Adsorption studies were performed under different conditions in a batch system (i.e., medium pH, protein concentration, temperature and ionic strength). Maximum lysozyme adsorption amount of poly(GMA) and poly(GMA)-Cibacron Blue F3GA beads were 1.6 and 591.7 mg/g, respectively. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium adsorption capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. It was observed that after 10 adsorption-elution cycle, poly(GMA)-Cibacron Blue F3GA beads can be used without significant loss in lysozyme adsorption capacity. Purification of lysozyme from egg-white was also investigated. Purification of lysozyme was monitored by determining the lysozyme activity using Micrococcus lysodeikticus as substrate. The purity of the eluted lysozyme was analyzed by SDS-PAGE and found to be 88% with recovery about 79%. The specific activity of the eluted lysozyme was high as 43,600 U/mg.

Chromatographic and fluorometric study of interactions between thiophilic and hydrophobic ligands and tryptophan peptide homologues

The interactions of tryptophan and its peptide homologues with thiophilic ligands were studied in terms of their chromatographic retention and steady-state fluorescence under various conditions, and compared with non-polar structures typically regarded as pure hydrophobic ligands. The experimental results show that both non-polar and polar interactions are involved in what has been termed "thiophilic adsorption chromatography".

Effect of pH changes on water release values in hydrophobic interaction chromatographic systems

The effect on pH on protein binding in HIC systems was investigated. Isocratic experiments were carried out to determine the capacity factors of various proteins as a function of temperature, pH and salt type. This paper presents a framework based on the Maxwell linkage function for estimating the number of released water molecules during the adsorption/desorption process due to a change of buffer pH. This approach also enables one to predict the effect of pH change on the water released values upon binding at any temperature condition. The results indicate that the total number of released water molecules (delta nu) for a pH change increased more on aromatic surfaces (phenyl Sepharose) than on aliphatic resins (butyl Sepharose). The results also indicate that the total number of released water molecules (deltanu) for a pH change increased with salt concentration and when changing from chaotropic to kosmotropic salts. The (deltanu) values also increased as the buffer pH approached the protein's pI, and decreased away from its pI. This work helps to establish a framework for the investigation of pH effects on protein selectivity in HIC systems.

The mechanism by which fish antifreeze proteins cause thermal hysteresis

Antifreeze proteins are characterised by their ability to prevent ice from growing upon cooling below the bulk melting point. This displacement of the freezing temperature of ice is limited and at a sufficiently low temperature a rapid ice growth takes place. The separation of the melting and freezing temperature is usually referred to as thermal hysteresis, and the temperature of ice growth is referred to as the hysteresis freezing point. The hysteresis is supposed to be the result of an adsorption of antifreeze proteins to the crystal surface. This causes the ice to grow as convex surface regions between adjacent adsorbed antifreeze proteins, thus lowering the temperature at which the crystal can visibly expand. The model requires that the antifreeze proteins are irreversibly adsorbed onto the ice surface within the hysteresis gap. This presupposition is apparently in conflict with several characteristic features of the phenomenon; the absence of superheating of ice in the presence of antifreeze proteins, the dependence of the hysteresis activity on the concentration of antifreeze proteins and the different capacities of different types of antifreeze proteins to cause thermal hysteresis at equimolar concentrations. In addition, there are structural obstacles that apparently would preclude irreversible adsorption of the antifreeze proteins to the ice surface; the bond strength necessary for irreversible adsorption and the absence of a clearly defined surface to which the antifreeze proteins may adsorb. This article deals with these apparent conflicts between the prevailing theory and the empirical observations. We first review the mechanism of thermal hysteresis with some modifications: we explain the hysteresis as a result of vapour pressure equilibrium between the ice surface and the ambient fluid fraction within the hysteresis gap due to a pressure build-up within the convex growth zones, and the ice growth as the result of an ice surface nucleation event at the hysteresis freezing point. We then go on to summarise the empirical data to show that the dependence of the hysteresis on the concentration of antifreeze proteins arises from an equilibrium exchange of antifreeze proteins between ice and solution at the melting point. This reversible association between antifreeze proteins and the ice is followed by an irreversible adsorption of the antifreeze proteins onto a newly formed crystal plane when the temperature is lowered below the melting point. The formation of the crystal plane is due to a solidification of the interfacial region, and the necessary bond strength is provided by the protein "freezing" to the surface. In essence: the antifreeze proteins are "melted off" the ice at the bulk melting point and "freeze" to the ice as the temperature is reduced to subfreezing temperatures. We explain the different hysteresis activities caused by different types of antifreeze proteins at equimolar concentrations as a consequence of their solubility features during the phase of reversible association between the proteins and the ice, i.e., at the melting point; a low water solubility results in a large fraction of the proteins being associated with the ice at the melting point. This leads to a greater density of irreversibly adsorbed antifreeze proteins at the ice surface when the temperature drops, and thus to a greater hysteresis activity. Reference is also made to observations on insect antifreeze proteins to emphasise the general validity of this approach.

Magnetic Dye Affinity Beads for the Adsorption ofβ-Casein

Casein is well known as a good protein emulsifier and beta-casein is the major component of casein and commercial sodium caseinate. Dye affinity adsorption is increasingly used for protein separation. beta-Casein adsorption onto Reactive Red 120 attached magnetic poly(2-hydroxyethyl methacrylate) (m-PHEMA) beads was investigated in this work. m-PHEMA beads (80-120 microm in diameter) were produced by dispersion polymerization. The dichlorotriazine dye Reactive Red 120 was attached covalently as a ligand. The dye attached beads, having a swelling ratio of 55% (w/w) and carrying different amounts of Reactive Red 120 (9.2 micromol . g(-1)-39.8 micromol . g(-1)), were used in beta-casein adsorption studies. The effects of the initial concentration, pH, ionic strength and temperature on the adsorption efficiency of dye attached beads were studied in a batch reactor. The non-specific adsorption on the m-PHEMA beads was 1.4 mg . g(-1). Reactive Red 120 attachment significantly increased the beta-casein adsorption up to 37.3 mg . g(-1). More than 95.4% of the adsorbed beta-casein was desorbed in 1 h in a desorption medium containing 1.0 M KSCN at pH 8.0. We concluded that Reactive Red 120 attached m-PHEMA beads can be applied for beta-casein adsorption without significant losses in the adsorption capacities.

Effect of Spacer Arm Length on Protein Retention on a Strong Cation Exchange Adsorbent

The retention of five proteins was compared on a set of three strong cation exchange adsorbents that differed in spacer arm chemical structure and length. The adsorbents included a commercial product, Amersham Biosciences SP Sepharose Fast Flow, containing a six-carbon spacer between the agarose matrix and the anionic ligand, and two custom-prepared materials. One of the custom adsorbents contained a spacer of about half the length of the SP Sepharose Fast Flow, and the other contained no spacer arm. The adsorbent with no spacer arm was found to be significantly more retentive for all of the test proteins examined, in both isocratic and gradient elution tests. Reducing the spacer arm length by half resulted in increased retention for four of the five proteins, but this increase was less than what was observed when the spacer arm was eliminated. Retention increases were obtained without increasing the density of the anionic charge groups and appear to result from an enhancement of electrostatic or secondary nonelectrostatic interactions, or both. The results indicate that spacer arm length may be a useful variable in manipulating stationary-phase retention properties.

Evaluation of n-valeraldehyde modified chitosan as a matrix for hydrophobic interaction chromatography

The n-valeraldehyde modified Chitosan (pentyl-Chitosan CL) was prepared by Schiff-base formation and hydrogenation. By studying the IR spectra of Chitosan and pentyl-Chitosan CL, it is suggested that a pentyl group is linked to 2'-NH, by a C-N bond. The influence of temperature and ionic strength on the adsorption of protein on pentyl-Chitosan CL were studied, and it was found that the behavior of adsorption met with the theory of hydrophobic interaction. The storage stability of these packing materials was also investigated, the results show storage in 20% ethanol at 4 degrees C is the most suitable condition. Alpha-amylase was purified successfully by hydrophobic interaction chromatography, using pentyl-Chitosan CL as hydrophobic matrix. The purification factor is about 2.5 and the recovery is over 82%.

Hydrophobic interaction chromatography of proteins

In this article, an overview of hydrophobic interaction chromatography (HIC) of proteins is given. After a brief description of protein hydrophobicity and hydrophobic interactions, we present the different proposed theories for the retention mechanism of proteins in HIC. Additionally, the main parameters to consider for the optimization of fractionation processes by HIC and the stationary phases available were described. Selected examples of protein fractionation by HIC are also presented.

Hydrophobic interaction chromatography of human serum alpha1-antitrypsin and alpha1-acid glycoprotein

The relative hydrophobicity of human serum alpha1-antitrypsin (AAT) and alpha1-acid glycoprotein (AGP) in comparison to various reference proteins was determined by hydrophobic interaction chromatography (HIC). Apolar character of glycoproteins was generated using three different cosmotropic salts, ammonium sulfate, sodium sulfate, sodium citrate and isocratic, or reversed linear gradient elution techniques. Human serum AAT and AGP showed different apolar properties on Fractogel EMD phenyl and propyl columns modulated either by the type and concentration of cosmotropic salts, or by the pH of the mobile phase. According to its higher carbohydrate content AGP proved to be more polar than AAT. Human serum AAT and AGP were pre-separated by Cibacron Blue F3G-A dye ligand affinity chromatography and based on their different hydrophobicity were fractionated and purified by HIC.

Hydrophobic interaction chromatography of Chromobacterium viscosum lipase on polypropylene glycol immobilised on Sepharose

The fractionation of Chromobacterium viscosum lipase was performed using a polypropylene glycol-Sepharose gel. The influence of mobile phase composition on the adsorption of lipase on the gel was studied and it was found that the retention of lipase depends on the salt used and increased with increasing the ionic strength. The retention was not strongly affected by changing the pH value of the mobile phase. By using 20% (w/v) ammonium sulphate in phosphate buffer a total retention of lipase on the column was obtained and by simply decreasing the ionic strength of the buffer, desorption of lipase could be achieved. The chromatographic purification of Chromobacterium viscosum lipase by hydrophobic interaction chromatography on Sepharose CL-6B modified by covalent immobilisation of 1,4-butanediol diglycidyl ether, polyethylene glycol and polypropylene glycol was also compared.

Effect of mobile phase composition on selectivity in preparative hydrophobic interaction chromatographic purification of glucagon

A weakly hydrophobic acrylester copolymer, Amberlite XAD-7, has been used in the purification process of glucagon production for elimination of protein impurities in the crude glucagon fractions, obtained from the industrial waste from insulin production. Varying the mobile phases composition, it was shown that suitable selectivity for the separation of proteins under non-denaturing conditions can be achieved. The purified glucagon, obtained at the proposed chromatographic conditions has a biological activity of above 1 IU/mg.

Calculation of the molecular masses of two newly synthesized thermostable enzymes isolated from thermophilic microorganisms

Two thermostable enzymes synthesized by thermophilic microorganisms were isolated and purified. A thermostable beta-galactosidase was produced in a continuous fermentation process by Bacillus stearothermophilus TP 32 as an intracellular enzyme. After applying different concentration procedures the raw extract enzyme was prepurified on a Sephadex G-200 size exclusion column. The isolated beta-galactosidase fraction was then separated with HPLC on a TSK G 3000 SW size exclusion column to determine the molecular mass based on calibration curves of standard proteins. The other enzyme, a thermostable protease, was synthesized by Bacillus stearothermophilus TP 26 as an extracellular enzyme. After its concentration, the enzyme was purified on a classical size exclusion column (Sephacryl S-200) and on a HPLC size exclusion column (BIO-SIL TSK-250). The micropreparatively isolated fraction was separated again on this HPLC column to determine its molecular mass. The optimum temperature of both enzymes was approximately 75 degrees C.