Hydrophobic (interaction) chromatography

Identification of monoclonal antibody variants involved in aggregate formation - Part 2: Hydrophobicity variants

Monoclonal antibodies (mAbs) are valuable tools both in therapy and in diagnostic. Their tendency to aggregate is a serious concern. Since a mAb drug substance (DS) is composed of different variants, it is important for manufacturers to know the behavior and stability not only of the mAb as a whole, but also of the variants contained in the product. We present a method to separate hydrophobicity variants of a mAb and subsequently analyzed these variants for stability and aggregation propensity. We identified a potentially aggregation prone hydrophilic variant which is interrelated with another previously identified aggregation prone acidic charge variant. Additionally, we assessed the risk posed by the aggregation prone variant to the DS by spiking hydrophobicity variants into DS and did not observe an enhanced aggregation propensity. Thus we present an approach to separate, characterize and analyze the criticality of aggregation prone variants in protein DS which is a step forward to further assure drug safety.

Hydrophobic Interaction Chromatography

Most proteins and large polypeptides have hydrophobic regions at their surface. These hydrophobic "patches" are due to the presence of the side chains of hydrophobic or nonpolar amino acids such as phenylalanine, tryptophan, alanine, and methionine. These surface hydrophobic regions are interspersed between more hydrophilic or polar regions and the number, size, and distribution of them is a specific characteristic of each individual protein. Hydrophobic Interaction Chromatography (HIC) is a commonly used technique that exploits these hydrophobic features of proteins as a basis for their separation even in complex biological mixtures (Queiroz et al., J Biotechnol 87:143-159, 2001; Eisenberg and McLachlan, Nature 319:199-203, 1986). In general, the conditions under which hydrophobic interaction chromatography is used are relatively mild and "protein friendly" resulting in good biological recoveries. Hydrophobic binding is relatively strong and is maintained even in the presence of chaotropic agents, organic solvents, and detergents. For these reasons, this technique has a widespread use for the purification of proteins and large polypeptides.

Surface Tensions of Proteins in Aqueous Solutions

Changes in conformation of proteins in solution may be detected by determin ing the relative surface tensions of their solutions. Of the proteins examined, all of the enzymes had distinct changes in surface tensions upon going from a 3M NaCl medium to a salt-free aqueous solution. Only two of the seven non- enzymic proteins underwent detectable changes in the same cycle. These relative surface tensions could be of value in determining adsorption/elution profiles for hydrophobic interaction chromatography.

Computer assisted liquid chromatographic method development for the separation of therapeutic proteins

This review summarizes the use of computer assisted liquid chromatographic method development for the analytical characterization of protein biopharmaceuticals.

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%.

Peptide adsorption on silica nanoparticles: evidence of hydrophobic interactions

Molecular recognition and interactions at the interface between biomolecules and inorganic materials determine important phenomena such as protein adsorption, cell adhesion to biomaterials, or the selective response of biosensors. Events occurring at the biomolecule-inorganic interface, despite their importance, are still poorly understood, thus limiting control of interfacial properties and response. In this contribution, using well-characterized silica nanoparticles and a series of peptides having heterogeneous physicochemical properties (S1: KLPGWSG, S2: AFILPTG, and S3: LDHSLHS) identified from biopanning against the same particles, we identify the driving forces that govern peptide-silica binding. Binding isotherms obtained by fluorimetric assay under different pH conditions allowed us to demonstrate the impact of binding environment (pH) on adsorption behavior of a given peptide-surface silica nanoparticle. Our experimental data suggest a multistep adsorption mechanism leading to the formation of multilayers on silica, in which the prevailing interactions (i.e., electrostatic or hydrophobic/hydrogen bonding) and their relative contribution to the binding event are governed by the identity of the peptide itself, the substrate's surface functionality (hydrophilic or hydrophobic), and the peptide bulk concentration and solution bulk pH. Our studies show how it is possible to modulate peptide uptake on silica, or in fact on any particle, by changing either the surface properties or, more simply, the binding environment. In addition, the data reveal an intrinsic bias toward positively charged sequences in the elution conditions used in the biopanning protocol with much information about strong binder sequence diversity being lost during panning.

Hydrophobic interaction chromatography

Most proteins and large polypeptides have hydrophobic regions at their surface. These hydrophobic "patches" are due to the presence of the side chains of hydrophobic or nonpolar amino acids such as phenylalanine, tryptophan, alanine, and methionine. These surface hydrophobic regions are interspersed between more hydrophilic and polar regions, and the number, size, and distribution of them are a specific characteristic of each protein. Hydrophobic interaction chromatography (HIC) is a commonly used technique that exploits these hydrophobic features of proteins as a basis for their separation even in complex biological mixtures (Queiroz et al., J Biotechnol 87:143-159, 2001; Eisenberg and McLachlan, Nature 319:199-203, 1986). In general, the conditions under which HIC is used are relatively mild and "protein friendly" resulting in good biological recoveries. Hydrophobic binding is relatively strong and is maintained even in the presence of chaotropic agents, organic solvents, and detergents. For these reasons, this technique has a widespread use for the purification of proteins and large polypeptides.

Hydrophobic interactions involved in attachment of a baculovirus to hydrophobic surfaces

The hydrophobic interactions of Trichoplusia ni nuclear polyhedrosis virus were characterized by hydrophobic interaction chromatography. The determination of the hydrophobic force and some of the factors that influence its size is discussed in relation to the attachment to leaf surfaces of polyhedra during their use as biological control agents against insect pests.

Mechanistic analysis on the effects of salt concentration and pH on protein adsorption onto a mixed-mode adsorbent with cation ligand

Streamline Direct HST is a new kind of mixed-mode adsorbent with cation exchange ligand, especially developed for the expanded bed adsorption process, which can capture target protein directly from the moderate ionic strength feedstock without the need of dilution or other additives. In this study, the isotherm adsorption behaviors and the isocratic retention factors of bovine serum albumin (BSA) on Streamline Direct HST were measured, and the corresponding adsorption mechanisms were also described. The results indicated that Streamline Direct HST shows the typical property of salt-independent adsorption and the maximum binding capacity of BSA occurs near the isoelectric point of BSA. When there are some amounts of electrostatic repulsion protein-adsorbent interactions, the multilayer adsorption could be found, and high salt concentration does not favor the adsorption of protein. A patch-controlled adsorption process and an oriented adsorption model are proposed for describing the adsorption behaviors under electrostatic repulsion condition.

Hydrophobic interaction chromatography of proteins. II. Binding capacity, recovery and mass transfer properties

Hydrophobic interaction chromatography media suited for large scale separations were compared regarding dynamic binding capacity, recovery and mass transfer properties. In all cases, pore diffusion was the rate limiting step. Reduced heights equivalent to a theoretical plate for bovine serum albumin derived from breakthrough curves at reduced velocities between 60 and 1500 ranged from 10 to 700. Pore diffusion coefficients were derived from pulse response experiments for the model proteins alpha-lactalbumin, lysozyme, beta-lactoglobulin, bovine serum albumin and immunoglobulin G. Diffusivity of lysozyme did not follow the trend of decreasing diffusivity with increasing molecular mass, as observed for the rest of the proteins. In general, mass transfer coefficients were smaller compared to ion-exchange chromatography. Dynamic binding capacities for the model protein bovine serum albumin varied within a broad range. However, sorbents based on polymethacrylate showed a lower dynamic capacity than media based on Sepharose. Some sorbents could be clustered regarding binding capacity affected by salt. These sorbents exhibited a disproportional increase of binding capacity with increasing ammonium sulfate concentration. Recovery of proteins above 75% could be observed for all sorbents. Several sorbents showed a recovery close to 100%.

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%.

Salt-independent adsorption chromatography: new broad-spectrum affinity methods for protein capture

The role of chromatography in capture is reviewed in terms of the special requirements imposed by the processing of very crude feedstocks. Adsorption methods which are not significantly affected by variations of feedstock ionic strength are highlighted. Methods are compared in terms of simplicity, robustness, selectivity and ease of elution. The application of such methods to enzyme and antibody purifications is summarised. Particular emphasis is placed on high ligand density methods, which have potential for broad-spectrum application.

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.

Studies on the chromatographic fractionation of Trichoderma reesei cellulases by hydrophobic interaction

This work reports new studies on cellulases fractionation by hydrophobic interaction chromatography. The purification procedure for the Trichoderma reesei cellulase complex consists of gel permeation chromatography on Sephadex G-25M followed by an ultrafiltration step. The concentrated enzyme solution was then fractionated on Sepharose CL-6B modified by covalent immobilization of 1,4-butanediol diglycidyl ether. The influence of the mobile phase composition on the chromatographic behaviour of the T. reesei cellulase complex was investigated. By using 13% (w/v) ammonium sulphate in eluent buffer, a selective separation of beta-glucosidase with a two-fold increase in specific activity and a recovery of 60% cellobiase activity were obtained. Other commercial hydrophobic supports (octyl- and phenyl-Sepharose) were also tested and compared under the same conditions.

Effect of ionic strength on initial interactions of Escherichia coli with surfaces, studied on-line by a novel quartz crystal microbalance technique

A novel quartz crystal microbalance (QCM) technique was used to study the adhesion of nonfimbriated and fimbriated Escherichia coli mutant strains to hydrophilic and hydrophobic surfaces at different ionic strengths. This technique enabled us to measure both frequency shifts (Deltaf), i.e., the increase in mass on the surface, and dissipation shifts (DeltaD), i.e., the viscoelastic energy losses on the surface. Changes in the parameters measured by the extended QCM technique reflect the dynamic character of the adhesion process. We were able to show clear differences in the viscoelastic behavior of fimbriated and nonfimbriated cells attached to surfaces. The interactions between bacterial cells and quartz crystal surfaces at various ionic strengths followed different trends, depending on the cell surface structures in direct contact with the surface. While Deltaf and DeltaD per attached cell increased for nonfimbriated cells with increasing ionic strengths (particularly on hydrophobic surfaces), the adhesion of the fimbriated strain caused only low-level frequency and dissipation shifts on both kinds of surfaces at all ionic strengths tested. We propose that nonfimbriated cells may get better contact with increasing ionic strengths due to an increased area of contact between the cell and the surface, whereas fimbriated cells seem to have a flexible contact with the surface at all ionic strengths tested. The area of contact between fimbriated cells and the surface does not increase with increasing ionic strengths, but on hydrophobic surfaces each contact point seems to contribute relatively more to the total energy loss. Independent of ionic strength, attached cells undergo time-dependent interactions with the surface leading to increased contact area and viscoelastic losses per cell, which may be due to the establishment of a more intimate contact between the cell and the surface. Hence, the extended QCM technique provides new qualitative information about the direct contact of bacterial cells to surfaces and the adhesion mechanisms involved.

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.

Binding of proteins to copolymers of varying hydrophobicity

Hydrophobic interactions between proteins and amphiphilic polyelectrolytes were studied by frontal analysis continuous capillary electrophoresis (Gao et al., Analytical Chemistry, 1997, Vol. 69, pp. 2945-2951). Binding isotherms were obtained for beta-lactoglobulin and for bovine serum albumin interacting with a series of alternating copolymers of maleic acid and alkyl-vinyl ethers of varying hydrophobicity. Although binding between proteins and copolymers increases with increasing alkyl chain length, a minimum alkyl chain length of 3-4 methylenes is required for significant hydrophobic interactions to occur. These copolymers, like other polyamphiphiles, can form intrapolymer micelles, and the extent of such micellization decreases with increasing degree of carboxylate ionization. Binding results obtained at different pHs suggest that competition exists between intrapolymer micelle formation and protein-polymer hydrophobic interactions.

Hydrophobic charge induction chromatography: salt independent protein adsorption and facile elution with aqueous buffers

A new form of protein chromatography, hydrophobic charge induction, is described. Matrices prepared by attachment of weak acid and base ligands were uncharged at absorption pH. At low ligand densities, protein adsorption was typically promoted with lyotropic salts. At higher ligand densities, chymosin, chymotrypsinogen and lysozyme were adsorbed independently of ionic strength. A pH change released the electrostatic potential of the matrix and weakened hydrophobic interactions, inducing elution. Matrix hydrophobicity and titration range could be matched to protein requirements by ligand choice and density. Both adsorption and elution could be carried out within the pH 5-9 range.

Haemocompatibility of invasive sensors

In recent years the importance and utilisation of invasive chemical sensors have increased, especially in respect to their function and behaviour in a biological environment. This review aims to highlight the development of various sensors and reflect on the problems which can occur when the sensors come into contact with blood. Thus their haemocompatibility is a key area of importance. A clear understanding of their interaction with plasma proteins at the point of interface is fundamental as this determines their ultimate capability to function safely and effectively. There is also an overview of various techniques that have been developed, together with a broad summary of inherent problems which may arise when aiming to improve the haemocompatibility of invasive sensors for in vivo applications.

Adsorption behaviour of lipase from Staphylococcus carnosus on a hydrophobic adsorbent

The adsorption of proteins on a solid surface with a subsequent desorption is a well known final purification step in downstream processing. Here the adsorption behaviour of a microbial lipase on the hydrophobic Fractogel TSK butyl 650 in a crude fermentation supernatant is investigated. The measured equilibrium curves differ from fermentation to fermentation by up to +/- 65%. The adsorption capacity increases with decreasing particle diameter of the adsorbent and is influenced by the method of contacting the supernatant with the adsorbent. The rate of desorption depends largely on the adsorption conditions, which is an indication of different orientations of the adsorbed enzyme.

Hydrophobic interaction chromatography of proteins on Separon hema. I. The effect of an initial salt concentration on the separation of proteins

The influence of an initial salt concentration, phi(0), on the gradient separation of proteins using hydrophobic interaction chromatography on Separon HEMA 1000 was investigated. The results obtained were compared with the retention times and peak widths calculated according to a mathematical model.

Simultaneous purification of hexokinase, class-I fructose-bisphosphate aldolase, triosephosphate isomerase and phosphoglycerate kinase from Trypanosoma brucei

A method is presented for the simultaneous purification of hexokinase, fructose-bisphosphate aldolase, triosephosphate isomerase and phosphoglycerate kinase, and the partial purification of glycerol-3-phosphate dehydrogenase (NAD+), 6-phosphofructokinase, glucosephosphate isomerase, and glycerol kinase from Trypanosoma brucei. As a first step, the glycosomes, microbody-like organelles of Trypanosomatidae, containing almost exclusively enzymes involved in glucose and glycerol metabolism [Opperdoes, F. R. and Borst, P. (1977) FEBS Lett. 80, 360-364], were purified eightfold from homogenates with an average yield of 38%. Subsequently, the glycosomal content was subjected to hydrophobic interaction chromatography on phenyl-Sepharose. This step results in pure hexokinase (15% final yield) and almost pure triosephosphate isomerase, while the other glycosomal enzymes elute as mixtures of two or three enzymes. Triosephosphate isomerase was further purified to homogeneity on CM-cellulose (33% final yield), while phosphoglycerate kinase and fructose-bisphosphate aldolase were separated from each other and purified to homogeneity by affinity chromatography using ATP-Sepharose (25% and 30% final yields, respectively). Fructose-bisphosphate aldolase was further characterized as a typical class I enzyme.

Separation of heparin on Sepharose CL-4B in the presence of high concentrations of ammonium sulphate

Heparin was fractionated by chromatography on Sepharose CL-4B/3.8-2.0 M ammonium sulphate in 0.01 M hydrochloric acid at 4 degrees C based on a principle different from that of gel filtration--possibly due to multiple interaction mechanisms including those based on hydrophobic bonds. The results of the fractionation were very similar to those of chromatography on Phenyl-Sepharose CL-4B/3.8-2.0 M ammonium sulphate in 0.01 M hydrochloric acid at room temperature. That is, the separation was related to the molecular size distribution, N-acetyl content and anticoagulant activities. As the result of studies on a set of Sepharose 4B gels with different degrees of cross-linking, it has been shown that the introduction of the cross-linked structure, -O-CH2-CH(OH)-CH2-O-, into the gel matrix enhances the interaction between the Sepharose CL-4B gel and heparin, indicating that heparin retention by the highly cross-linked Sepharose 4B gel surpasses that by Phenyl-Sepharose CL-4B.

Hydrophobic interaction chromatography of the rabbit uterine progesterone receptor

The chromatographic behavior of the rabbit uterine progesterone receptor interaction on several different hydrophobic matrices was characterized. Receptor, prepared in 0.6 M NaCl, exhibited a progressive retardation of elution, followed by retention, on a series of alkyl agarose columns as the length of the alkyl chain [(CH2)nH-] increased (n = 0-10), reflecting the presence of hydrophobic regions on the protein. Adsorption did not occur directly at the steroid binding site of the molecule and did not require activation to the DNA-binding form. Elution could be achieved by a decrease in the ionic strength of the buffer or the addition of glycerol, resulting in partial purification of receptor. Receptor bound tightly to phenyl agarose, although elution of the receptor under mild conditions (decreasing salt gradient, increasing glycerol gradient) resulted in poor yield and only modest purification. Passage of the non-activated progesterone receptor over Reactive Blue Sepharose effectively removed albumin, presumably by a hydrophobic interaction, although receptor was not retained. In the activated form, approximately 25% of receptor was bound to Reactive Blue Sepharose, reflecting an interaction of the Cibacron Blue dye with the polynucleotide binding site of the receptor. Hydrophobic chromatography may be an important adjunct to methods for purification of the progesterone receptor.

Characteristics of protein-aqueous medium interactions measured by partition in aqueous Ficoll-Dextran biphasic system

Partitioning of a number of proteins in the aqueous Ficoll-400-Dextran-70 biphasic system was studied at pH 7.4 under varied ionic compositions. The relative hydrophobicities of the proteins have been estimated, and the contributions of the interactions of the ionogenic and non-ionic groups of a protein with an aqueous environment to the total hydrophobicity of the protein have been evaluated. Some arguments in support of the biological significance of the effect of ionic composition on the relative hydrophobicity of biological macromolecules are given. Possible applications of the partition technique to protein research are discussed.