Hydrophobic interaction chromatography of proteins

The influence of mixed salts on the capacity of HIC adsorbers: A predictive correlation to the surface tension and the aggregation temperature

Hydrophobic interaction chromatography (HIC) is one of the most frequently used purification methods in downstream processing of biopharmaceuticals. During HIC, salts are the governing additives contributing to binding strength, binding capacity, and protein solubility in the liquid phase. A relatively recent approach to increase the dynamic binding capacity (DBC) of HIC adsorbers is the use of salt mixtures. By mixing chaotropic with kosmotropic salts, the DBC can strongly be influenced. For salt mixtures with a higher proportion of chaotropic than kosmotropic salt, higher DBCs were achieved compared with single salt approaches. By measuring the surface tensions of the protein salt solutions, the cavity theory-proposed by Melander and Horváth-that higher surface tensions lead to higher DBCs, was found to be invalid for salt mixtures. Aggregation temperatures of lysozyme in the salt mixtures, as a degree of hydrophobic forces, were correlated to the DBCs. Measuring the aggregation temperatures has proven to be a fast analytical methodology to estimate the hydrophobic interactions and thus can be used as a measure for an increase or decrease in the DBCs. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:346-354, 2016.

Online Hydrophobic Interaction Chromatography-Mass Spectrometry for Top-Down Proteomics

Recent progress in top-down proteomics has led to a demand for mass spectrometry (MS)-compatible chromatography techniques to separate intact proteins using volatile mobile phases. Conventional hydrophobic interaction chromatography (HIC) provides high-resolution separation of proteins under nondenaturing conditions but requires high concentrations of nonvolatile salts. Herein, we introduce a series of more-hydrophobic HIC materials that can retain proteins using MS-compatible concentrations of ammonium acetate. The new HIC materials appear to function as a hybrid form of conventional HIC and reverse phase chromatography. The function of the salt seems to be preserving protein structure rather than promoting retention. Online HIC-MS is feasible for both qualitative and quantitative analysis. This is demonstrated with standard proteins and a complex cell lysate. The mass spectra of proteins from the online HIC-MS exhibit low charge-state distributions, consistent with those commonly observed in native MS. Furthermore, HIC-MS can chromatographically separate proteoforms differing by minor modifications. Hence, this new HIC-MS combination is promising for top-down proteomics.

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%.

Three dimensional liquid chromatography coupling ion exchange chromatography/hydrophobic interaction chromatography/reverse phase chromatography for effective protein separation in top-down proteomics

To address the complexity of the proteome in mass spectrometry (MS)-based top-down proteomics, multidimensional liquid chromatography (MDLC) strategies that can effectively separate proteins with high resolution and automation are highly desirable. Although various MDLC methods that can effectively separate peptides from protein digests exist, very few MDLC strategies, primarily consisting of 2DLC, are available for intact protein separation, which is insufficient to address the complexity of the proteome. We recently demonstrated that hydrophobic interaction chromatography (HIC) utilizing a MS-compatible salt can provide high resolution separation of intact proteins for top-down proteomics. Herein, we have developed a novel 3DLC strategy by coupling HIC with ion exchange chromatography (IEC) and reverse phase chromatography (RPC) for intact protein separation. We demonstrated that a 3D (IEC-HIC-RPC) approach greatly outperformed the conventional 2D IEC-RPC approach. For the same IEC fraction (out of 35 fractions) from a crude HEK 293 cell lysate, a total of 640 proteins were identified in the 3D approach (corresponding to 201 nonredundant proteins) as compared to 47 in the 2D approach, whereas simply prolonging the gradients in RPC in the 2D approach only led to minimal improvement in protein separation and identifications. Therefore, this novel 3DLC method has great potential for effective separation of intact proteins to achieve deep proteome coverage in top-down proteomics.

Examination of salivary proteins as biomarkers of pathological conditions. Literature review

Saliva is universally available biofluid, easy to collect. Comprehensive analysis and identification of the proteomic content of human saliva may contribute to the understanding of oral pathophysiology and provide a foundation for the recognition of potential biomarkers of human disease. These features make it an ideal biological material for the early detection of many diseases of different origin, and enable non-invasive diagnostics. The presence of protein markers in saliva was found with usage of capillary electrophoresis and mass spectrometry.

Separation of mAbs molecular variants by analytical hydrophobic interaction chromatography HPLC: overview and applications

Hydrophobic interaction chromatography-high performance liquid chromatography (HIC-HPLC) is a powerful analytical method used for the separation of molecular variants of therapeutic proteins. The method has been employed for monitoring various post-translational modifications, including proteolytic fragments and domain misfolding in etanercept (Enbrel®); tryptophan oxidation, aspartic acid isomerization, the formation of cyclic imide, and α amidated carboxy terminus in recombinant therapeutic monoclonal antibodies; and carboxy terminal heterogeneity and serine fucosylation in Fc and Fab fragments. HIC-HPLC is also a powerful analytical technique for the analysis of antibody-drug conjugates. Most current analytical columns, methods, and applications are described, and critical method parameters and suitability for operation in regulated environment are discussed, in this review.

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.

Effective protein separation by coupling hydrophobic interaction and reverse phase chromatography for top-down proteomics

One of the challenges in proteomics is the proteome's complexity, which necessitates the fractionation of proteins prior to the mass spectrometry (MS) analysis. Despite recent advances in top-down proteomics, separation of intact proteins remains challenging. Hydrophobic interaction chromatography (HIC) appears to be a promising method that provides high-resolution separation of intact proteins, but unfortunately the salts conventionally used for HIC are incompatible with MS. In this study, we have identified ammonium tartrate as a MS-compatible salt for HIC with comparable separation performance as the conventionally used ammonium sulfate. Furthermore, we found that the selectivity obtained with ammonium tartrate in the HIC mobile phases is orthogonal to that of reverse phase chromatography (RPC). By coupling HIC and RPC as a novel two-dimensional chromatographic method, we have achieved effective high-resolution intact protein separation as demonstrated with standard protein mixtures and a complex cell lysate. Subsequently, the separated intact proteins were identified by high-resolution top-down MS. For the first time, these results have shown the high potential of HIC as a high-resolution protein separation method for top-down proteomics.

Fusion tags for protein solubility, purification and immunogenicity in Escherichia coli: the novel Fh8 system

Proteins are now widely produced in diverse microbial cell factories. The Escherichia coli is still the dominant host for recombinant protein production but, as a bacterial cell, it also has its issues: the aggregation of foreign proteins into insoluble inclusion bodies is perhaps the main limiting factor of the E. coli expression system. Conversely, E. coli benefits of cost, ease of use and scale make it essential to design new approaches directed for improved recombinant protein production in this host cell. With the aid of genetic and protein engineering novel tailored-made strategies can be designed to suit user or process requirements. Gene fusion technology has been widely used for the improvement of soluble protein production and/or purification in E. coli, and for increasing peptide's immunogenicity as well. New fusion partners are constantly emerging and complementing the traditional solutions, as for instance, the Fh8 fusion tag that has been recently studied and ranked among the best solubility enhancer partners. In this review, we provide an overview of current strategies to improve recombinant protein production in E. coli, including the key factors for successful protein production, highlighting soluble protein production, and a comprehensive summary of the latest available and traditionally used gene fusion technologies. A special emphasis is given to the recently discovered Fh8 fusion system that can be used for soluble protein production, purification, and immunogenicity in E. coli. The number of existing fusion tags will probably increase in the next few years, and efforts should be taken to better understand how fusion tags act in E. coli. This knowledge will undoubtedly drive the development of new tailored-made tools for protein production in this bacterial system.

Fusion tags for protein solubility, purification and immunogenicity in Escherichia coli: the novel Fh8 system

Proteins are now widely produced in diverse microbial cell factories. The Escherichia coli is still the dominant host for recombinant protein production but, as a bacterial cell, it also has its issues: the aggregation of foreign proteins into insoluble inclusion bodies is perhaps the main limiting factor of the E. coli expression system. Conversely, E. coli benefits of cost, ease of use and scale make it essential to design new approaches directed for improved recombinant protein production in this host cell. With the aid of genetic and protein engineering novel tailored-made strategies can be designed to suit user or process requirements. Gene fusion technology has been widely used for the improvement of soluble protein production and/or purification in E. coli, and for increasing peptide's immunogenicity as well. New fusion partners are constantly emerging and complementing the traditional solutions, as for instance, the Fh8 fusion tag that has been recently studied and ranked among the best solubility enhancer partners. In this review, we provide an overview of current strategies to improve recombinant protein production in E. coli, including the key factors for successful protein production, highlighting soluble protein production, and a comprehensive summary of the latest available and traditionally used gene fusion technologies. A special emphasis is given to the recently discovered Fh8 fusion system that can be used for soluble protein production, purification, and immunogenicity in E. coli. The number of existing fusion tags will probably increase in the next few years, and efforts should be taken to better understand how fusion tags act in E. coli. This knowledge will undoubtedly drive the development of new tailored-made tools for protein production in this bacterial system.

The role of ligands on protein retention in adsorption chromatography: a surface energetics approach

Protein adsorption onto hydrophobic chromatographic supports has been investigated using a colloid theory surface energetics approach. The surface properties of commercially available chromatographic beads, Toyopearl Phenyl 650-C, and Toyopearl Butyl 650-C, have been experimentally determined by contact angle and zeta potential measurements. The adsorption characteristics of these beads, which bear the same backbone matrix but harbor different ligands, have been studied toward selected model proteins, in the hydrated as well as dehydrated state. There were two prominent groups of proteins observed with respect to the chromatographic supports presented in this work: loosely retained proteins, which were expected to have lower average interaction energies, and the strongly retained proteins, which were expected to have higher average interaction energies. Results were also compared and contrasted with calculations derived from adsorbent surface energies determined by inverse liquid chromatography. These results showed a good qualitative agreement, and the interaction energy minima obtained from these extended Derjaguin, Landau, Verwey and Overbeek calculations were shown to correlate well with the experimentally determined adsorption behavior of each protein.

Calcium-dependent structural changes in human reticulocalbin-1

Human reticulocalbin-1 (hRCN1) has six EF-hand motifs and binds Ca(2+). hRCN1 is a member of the CREC family localized in the secretory pathway, and its cellular function remains unclear. In this study, we established a new bacterial expression and purification procedure for hRCN1. We observed that hRCN1 binds Ca(2+) in a cooperative manner and the Ca(2+) binding caused an increase in the α-helix content of hRCN1. On the other hand, hRCN1 did not change the structure with Mg(2+) loading. hRCN1 is a monomeric protein, and its overall structure became more compact upon Ca(2+) binding, as revealed by gel-filtration column chromatography and small-angle X-ray scattering. This is the first report of conformational changes in the CREC family upon Ca(2+) binding. Our data suggest that CREC family member interactions with target proteins are regulated in the secretory pathway by conformational changes upon Ca(2+) binding.

The Fh8 tag: a fusion partner for simple and cost-effective protein purification in Escherichia coli

Downstream processing is still a major bottleneck in recombinant protein production representing most of its costs. Hence, there is a continuing demand of novel and cost-effective purification processes aiming at the recovery of pure and active target protein. In this work, a novel purification methodology is presented, using the Fh8 solubility enhancer tag as fusion handle. The binding properties of Fh8 tag to a hydrophobic matrix were first studied via hydrophobic interaction chromatography (HIC). The Fh8 tag was then evaluated as a purification handle by its fusion to green fluorescent protein and superoxide dismutase. The purification efficiency of the Fh8-HIC strategy was compared to the immobilized metal ion affinity chromatography (IMAC) using the His6 tag. Results showed that the Fh8-HIC binding mechanism is calcium-dependent in a low salt medium, making the purification process highly selective. Both target proteins were biologically active, even when fused to Fh8, and were successfully purified by HIC, achieving efficiencies identical to those of IMAC. Thus, the Fh8 acts as an effective affinity tag that, together with its previously reported solubility enhancer capability, allows for the design of inexpensive and successful recombinant protein production processes in Escherichia coli.

Protein purification by aminosquarylium cyanine dye-affinity chromatography

The most selective purification method for proteins and other biomolecules is affinity chromatography. This method is based on the unique biological-based specificity of the biomolecule-ligand interaction and commonly uses biological ligands. However, these ligands may present some drawbacks, mainly because of their cost and lability. Dye-affinity chromatography overcomes the limitations of biological ligands and is widely used owing to the low cost of synthetic dyes and to their resistance to biological and chemical degradation. In this work, immobilized aminosquarylium cyanine dyes are used in order to exploit affinity interactions with standard proteins such as lysozyme, α-chymotrypsin and trypsin. These studies evaluate the affinity interactions occurring between the immobilized ligand and the different proteins, as a reflection of the sum of several molecular interactions, namely ionic, hydrophobic and van der Waals, spread throughout the structure, in a defined spatial manner. The results show the possibility of using an aminosquarylium cyanine dye bearing a N-hexyl pendant chain, with a ligand density of 1.8 × 10(-2) mmol of dye/g of chromatographic support, to isolate lysozyme, α-chymotrypsin and trypsin from a mixture. The application of a decreasing ammonium sulfate gradient resulted in the recovery of lysozyme in the flowthrough. On the other hand, α-chymotrypsin and trypsin were retained, involving different interactions with the ligand. In conclusion, this study demonstrates the potential applicability of ligands such as aminosquarylium cyanine dyes for the separation and purification of proteins by affinity chromatography.

Strategies to characterize fungal lipases for applications in medicine and dairy industry

Lipases are water-soluble enzymes that act on insoluble substrates and catalyze the hydrolysis of long-chain triglycerides. Lipases play a vital role in the food, detergent, chemical, and pharmaceutical industries. In the past, fungal lipases gained significant attention in the industries due to their substrate specificity and stability under varied chemical and physical conditions. Fungal enzymes are extracellular in nature, and they can be extracted easily, which significantly reduces the cost and makes this source preferable over bacteria. Soil contaminated with spillage from the products of oil and dairy harbors fungal species, which have the potential to secrete lipases to degrade fats and oils. Herein, the strategies involved in the characterization of fungal lipases, capable of degrading fatty substances, are narrated with a focus on further applications.

Cloning, overexpression, purification, and characterization of a polyextremophilic β-galactosidase from the Antarctic haloarchaeon Halorubrum lacusprofundi

Background

Halorubrum lacusprofundi is a cold-adapted halophilic archaeon isolated from Deep Lake, a perennially cold and hypersaline lake in Antarctica. Its genome sequencing project was recently completed, providing access to many genes predicted to encode polyextremophilic enzymes active in both extremely high salinity and cold temperatures.

Results

Analysis of the genome sequence of H. lacusprofundi showed a gene cluster for carbohydrate utilization containing a glycoside hydrolase family 42 β-galactosidase gene, named bga. In order to study the biochemical properties of the β-galactosidase enzyme, the bga gene was PCR amplified, cloned, and expressed in the genetically tractable haloarchaeon Halobacterium sp. NRC-1 under the control of a cold shock protein (cspD2) gene promoter. The recombinant β-galactosidase protein was produced at 20-fold higher levels compared to H. lacusprofundi, purified using gel filtration and hydrophobic interaction chromatography, and identified by SDS-PAGE, LC-MS/MS, and ONPG hydrolysis activity. The purified enzyme was found to be active over a wide temperature range (−5 to 60°C) with an optimum of 50°C, and 10% of its maximum activity at 4°C. The enzyme also exhibited extremely halophilic character, with maximal activity in either 4 M NaCl or KCl. The polyextremophilic β-galactosidase was also stable and active in 10–20% alcohol-aqueous solutions, containing methanol, ethanol, n-butanol, or isoamyl alcohol.

Conclusion

The H. lacusprofundi β-galactosidase is a polyextremophilic enzyme active in high salt concentrations and low and high temperature. The enzyme is also active in aqueous-organic mixed solvents, with potential applications in synthetic chemistry. H. lacuprofundi proteins represent a significant biotechnology resource and for developing insights into enzyme catalysis under water limiting conditions. This study provides a system for better understanding how H. lacusprofundi is successful in a perennially cold, hypersaline environment, with relevance to astrobiology.

Hydrophobic interaction chromatography to analyze glycoproteins

Hydrophobic interaction chromatography (HIC) is one of many separation techniques that can be used to analyze proteins. The separation mechanism is based on the adsorption of the hydrophobic region of the protein to the hydrophobic ligands attached to the column in the presence of high salt. The proteins are then eluted by descending salt concentration. Here we describe the use of this HIC technique to evaluate the hydrophobicity of different monoclonal antibodies (mAbs) and to separate different heterogeneities that occur in mAb.