Separation of full and empty adeno-associated virus capsids by anion-exchange chromatography using choline-type salts

Development of clinically desirable adeno-associated virus (AAV) vectors with optimal genome design requires rapid and accurate analytical methods to assess AAV quality. Anion-exchange (AEX) chromatography provides a powerful analytical method for full/empty AAV capsid ratio determination. However, the current AEX methodology for separation of empty and full AAV capsids largely relies on the use of the highly toxic tetramethylammonium chloride (TMAC). Here, we describe a novel analytical AEX method for separation of empty and full AAV capsids that uses only non-toxic, choline-type compounds that contain structural similarity to the quaternary ammonium ligand present on the surface of AEX resin. Choline-Cl gradient, combined with sensitive fluorescence detection, allowed a safe and effective separation of empty and full AAV capsids with reproducible empty/full ratio determination. The choline-based assay was suitable for commonly used serotypes, AAV2, AAV5, AAV6, and AAV8. The limit of detection was ∼3.9 × 108 virus particles in the assay. A gradient-hold step-gradient elution with choline-Cl resulted in enhanced baseline separation of empty and full AAV8 capsids. In summary, the use of choline-Cl in the AEX assay is recommended for empty/full capsid ratio determination and other applications in AAV production, and it eliminates the necessity of using toxic TMAC.

Comparison of LC-MS-based methods for the determination of carboxylic acids in animal matrices

Carboxylic acids (CAs) are key players in human and animal metabolism. As they are hardly retained under reversed-phase liquid chromatography (RP-LC) conditions in their native form, derivatization is an option to make them accessible to RP-LC and simultaneously increase their response for mass spectrometric detection. In this work, two RP-LC tandem mass spectrometry-based methods using aniline or 3-nitrophenylhydrazine (3-NPH) as derivatization agents were compared with respect to several factors including completeness of derivatization, apparent recoveries (RAs) in both cow feces and ruminal fluid, and concentrations obtained in feces and ruminal fluid of cows. Anion exchange chromatography coupled to high-resolution mass spectrometry (AIC-HR-MS) served as reference method. Derivatization efficiencies were close to 100% for 3-NPH derivatization but variable (20-100%) and different in solvent solutions and matrix extracts for aniline derivatization. Likewise, average RAs of 13C-labeled short-chain fatty acids as internal standards were around 100% for 3-NPH derivatization but only 45% for aniline derivatization. Quantification of CAs in feces and ruminal fluid of cows initially fed a forage-only diet and then transitioned to a 65% high-grain diet which yielded similar concentrations for 3-NPH derivatization and AIC-HR-MS, but concentrations determined by aniline derivatization were on average five times lower. For these reasons, derivatization with aniline is not recommended for the quantitative analysis of CAs in animal samples.

Preparation of Jellyfish Mucin

A mucin-type glycoprotein extracted from various species of jellyfish (JF) is named qniumucin (Q-mucin). Compared with general mucins, most of which are from mammals including humans, Q-mucin can be collected on a relatively large scale with high yield. Owing to its simple structure with low heterogeneity, Q-mucin has a potential to be developed into material mucins which opens various applications valuable to humans. On the basis of our present knowledge, here, we describe our protocol for the extraction of Q-mucin, which can be extracted from any JF species worldwide. Experimental protocols to identify the structure of Q-mucin are also introduced.

Development of tandem cation exchange chromatography for high purity extracellular vesicle isolation: The effect of ligand steric availability

Purification of extracellular vesicles for research and therapeutic applications requires updated methodology to address the limitations of traditional ultracentrifugation and other size-based separation techniques. Their downfalls include induced extracellular vesicle aggregation, low yields, poor scalability and one-dimensionality of the separation process, as the size or sedimentation speed of extracellular vesicles is often the only selection criterion. Ion exchange chromatography is a promising alternative or supplementary method candidate, as it offers a different approach for extracellular vesicle separation, which is surface charge. For now, mostly anion exchange chromatography has been evaluated for extracellular vesicle purification, as it successfully relies on the strongly negative surface charge of extracellular vesicles. However, as extracellular vesicles are very complex in their structure, also cation exchange chromatography could be applicable, due to individual cationic domains on the extracellular vesicle surface. Here, we compare anion exchange chromatography to different types of cation exchange chromatography for the purification of platelet extracellular vesicle samples also containing plasma-derived impurities. We found that the choice of resin structure used for cation exchange chromatography is critical for binding platelet extracellular vesicles, as a conventional-type cation exchanger was found to only capture and elute less than 20% of extracellular vesicles. With the tentacle-type resin, it was possible to obtain comparable platelet extracellular vesicle yields (over 90%) with cation exchange chromatography compared to anion exchange chromatography, as well as superior purity, especially when it was combined to conventional cation exchange resin.

Evaluating orthogonality between ion-pair reversed phase, anion exchange, and hydrophilic interaction liquid chromatography for the separation of synthetic oligonucleotides

The orthogonality of separation between ion-pair reversed phase (IP-RP), anion exchange (AEX), and hydrophilic interaction liquid chromatography (HILIC) was evaluated for oligonucleotides. A polythymidine standard ladder was first used to evaluate the three methods and showed zero orthogonality, where retention and selectivity were based on oligonucleotide charge/size under all three conditions. Next, a model 23-mer synthetic oligonucleotide containing 4 phosphorothioate bonds with 2' fluoro and 2'-O-methyl ribose modifications typical of small interfering RNA was used for evaluating orthogonality. The resolution and orthogonality were evaluated between the three modes of chromatography in terms of selectivity differences for nine common impurities, including truncations (n-1, n-2), addition (n + 1), oxidation, and de-fluorination. We first evaluated different ion-pairing reagents that provided the best separation of the key impurities while suppressing diastereomer separation due to phosphorothioate linkages. Although different ion-pairing reagents affected resolution, very little orthogonality was observed. We then compared the retention times between IP-RP, HILIC, and AEX for each impurity of the model oligonucleotide and observed various selectivity changes. The results suggest that coupling HILIC with either AEX or IP-RP provide the highest degree of orthogonality due to the differences in retention for hydrophilic nucleobases and modifications under HILIC conditions. IP-RP provided the highest overall resolution for the impurity mixture, whereas more co-elution was observed with HILIC and AEX. The unique selectivity patterns offered by HILIC provides an interesting alternative to IP-RP or AEX, in addition to the potential for coupling with multidimensional separations. Future work should explore orthogonality for oligonucleotides with subtle sequence differences such as nucleobase modifications and base flip isomers, longer strands such as guide RNA and messenger RNA, and other biotherapeutic modalities such as peptides, antibodies, and antibody-drug-conjugates.

A comprehensive method for modeling and simulating ion exchange chromatography of complex mixtures

In recent years, many biological-based products have been developed, representing a significant fraction of income in the pharmaceutical market. Ion exchange chromatography is an important downstream step for the purification of target recombinant proteins present in clarified cell extracts, together with many other unknown impurities. This work develops a robust approach to model and simulate the purification of untagged heterologous proteins, so that the improved conditions to carry out an ion exchange chromatography are identified in a rational basis prior to the real purification run itself. Purification of the pneumococcal surface protein A (PspA4Pro) was used as a case study. This protein is produced by recombinant Escherichia coli and is a candidate for the manufacture of improved pneumococcal vaccines. The developed method combined experimental and computational procedures. Different anion exchange operating conditions were mapped in order to gather a broad range of representative experimental data. The equilibrium dispersive and the steric mass action equations were used to model and simulate the process. A training strategy to fit the model and separately describe the elution profiles of PspA4Pro and other proteins of the cell extract was applied. Based on the simulation results, a reduced ionic strength was applied for PspA4Pro elution, leading to increases of 14.9% and 11.5% for PspA4Pro recovery and purity, respectively, compared to the original elution profile. These results showed the potential of this method, which could be further applied to improve the performance of ion exchange chromatography in the purification of other target proteins under real process conditions.

Investigating purification and activity analysis of urease enzyme extracted from jack bean source: A green chemistry approach

Urease is an enzyme of historical importance in the field of biochemistry, generally microbial and plant urease is the primary sources of urease. The significant applications of urease enzyme are found to be foremost in food industry, medical equipment's and biosensors. In this work, urease has been extracted from Jack bean meal using ammonium sulphate and acetone precipitation. A significant amount of urease was precipitated and concentrated at 60% saturated solution of ammonium sulphate. The obtained precipitates were dissolved in 50 mM phosphate buffer (pH 8) after centrifugation, and subjected to sodium dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to determine the molecular weight of urease. Results obtained from the SDS-PAGE were validated using Zymography. Anion exchange chromatography was used to separate the desired protein at different pH (7.0, 7.5 and 8.0). The eluted fractions were assessed for urease activity using phenol-nitroprusside dependent ammonia release assay. Under these assay conditions, one unit of urease activity was calibrated as the amount of enzyme liberating 1 μM of NH3 from urea per unit time. The eluted fraction and Zymography analysis show the purified urease observed at 90 kDa and activity of purified urease, respectively. The obtained results for specific activity (173.67Units mg) and % purification (99.71%) for urease has been compared with the available literature, which are found to be in close relation with existing results. The proposed method is a novel approach which has recorded highest % purification and specific activity. Furthermore, it can be suitable for extracting urease from jack bean source for various industrial applications.

Dendrimer-functionalized hydrothermal nanosized carbonaceous spheres as superior anion exchangers for ion chromatographic separation

Polyamidamine (PAMAM) dendrimer-functionalized hydrothermal nanosized carbonaceous spheres (HNCSs) were prepared and utilized as latexes for agglomerated anion exchange chromatography (AEC) stationary phase. The high-concentration and scalable production of monodisperse HNCSs (73-98 nm) was accomplished via the polyquaternium-7-assisted hydrothermal carbonization of fructose. The novel PAMAM-based quaternizations of HNCSs were designed by the amidation with PAMAM and epoxy-amine addition reaction with glycidol in aqueous solution. The mild functionalization condition leads to well-kept morphology of HNCSs, which forms one even latex layer on the sulfonated surface of polystyrene-divinylbenzene microbeads for the construction of AEC packing. Under isocratic elution, seven common inorganic anions and five organic acids were baseline separated in 9 min on prepared packing with efficiencies of 54,000-79,800 plates m^-1 and asymmetry factor (As) of 1.02-1.12. The obtained separation efficiency, peak symmetry, and analysis time were superior to reported or typical commercial counterparts. The quick separation of polarizable anions in 7 min and carbohydrates in 5 min could also be carried out with symmetrical peaks (As: 1.00-1.18) and high efficiencies (49,700-62,100 N/m). Favorable stability and reproducibility were proved by continuous flushing and injection. The constructed packings were further applied to the determination of thiosulfate and sulfate in water reducer, galacturonic acid in Angelica polysaccharide hydrolysate, and fluoride samples in 4 min.

Purification and characterization of chitinase produced by thermophilic fungi Thermomyces lanuginosus

BACKGROUND

In the past few years, the production of shrimp shell waste from the seafood processing industries has confronted a significant surge. Furthermore, insignificant dumping of waste has dangerous effects on both nature and human well-being. This marine waste contains a huge quantity of chitin which has several applications in different fields. The chitinase enzyme can achieve degradation of chitin, and the chitin itself can be used as the substrate as well for production of chitinase. In the current study, the chitinase enzyme was produced by Thermomyces lanuginosus. The extracellular chitinase was purified from crude extract using ammonium sulfate precipitation followed by DEAE-cellulose ion-exchange chromatography and Sephadex G-100 gel filtration chromatography. The stability and activity of chitinase with different pH, temperature, different times for a reaction, in the presence of different metal ions, and different concentration of enzyme and substrate were analyzed.

RESULT

The chitinase activity was found to be highest at pH 6.5, 50 °C, and 60 min after the reaction began. and the chitinase showed the highest activity and stability in the presence of β-mercaptoethanol (ME). The SDS-PAGE of denatured purified chitinase showed a protein band of 18 kDa.

CONCLUSION

The characterization study concludes that Cu²⁺, Hg²⁺, and EDTA have an inhibitory effect on chitinase activity, whereas β-ME acts as an activator for chitinase activity. The utilization of chitin to produce chitinase and the degradation of chitin using that chitinase enzyme would be an opportunity for bioremediation of shrimp shell waste.

Sustainable valorization of meat processing wastewater with synergetic eutectic mixture based purification of R-Phycoerythrin from porphyrium cruentium

Wastewater effluent from meat processing industries are enriched with nutrients but remain underutilized. Therefore, an efficient method was administered by employing this resource for the cultivation of Porphyreum cruentium. The cultured biomass was exposed to a one-step disruption and selective purification method using a protic deep eutectic solvent to obtain a commercially significant pigment, R-Phycoerythrin (R-PE). Six protic deep eutectic solvents (pDES) were synthesized and their thermophysical activity determined. A synergy between microwave and cavitation (MACE-DLPME) has been achieved for the effective recovery of these membrane proteins. The addition of pDES provides the selective medium for the concentration of R-PE. Optimization of the MACE-DLPME method yields 95.9% (w/w) of R-PE. Preparative size exclusion chromatography resulted in (28 µg/g) of R-PE. Further ultra-purification by anion exchange chromatography enhances the purity fold of R-PE to 125. The resulting ultrapure fraction exhibits enhanced anti-platelet activity (1.56 mg/g ascorbic acid equivalent).

Determination of arsenic chemical species in rice grains using high-performance liquid chromatography coupled to hydride generator with atomic fluorescence detector (HPLC-HG-AFS)

The objective of this work is the validation and implementation of an analytical method for the determination of arsenic chemical species in rice grain samples using High-performance liquid chromatography coupled to a hydride generator with atomic fluorescence detector (HPLC-HG-AFS). The extraction protocol developed was based on HNO₃ 0.28 M (90 °C, 2 h), microwave-assisted. The results showed recovery percentages of arsenite (As (III)) (99–101%), arsenate (As (V)) (91–96%), dimethylarsinic acid (DMA) (92–102%) and monomethylarsonic acid (MMA) (94–97%). The precision of the method presented coefficients of variation lower than 7% and 8% for repeatability and reproducibility respectively. The detection limits were 2.5, 3.75, 7.5 and 4.0 µg kg⁻¹ for As (III), As (V), DMA and MMA respectively. The proposed methodology is reliable for the quantification of As species, because they are conserved during the extraction.•

The extraction protocol developed was based on Microwave-assisted acid extraction.

•

This methodology offers good sensitivity, precision, accuracy, detection and quantification limits.

•

It was successfully applied to determination of arsenic chemical species in rice grains.

Towards a more complete glycome: Advances in ion chromatography-mass spectrometry (IC-MS) for improved separation and analysis of carbohydrates

To date, few tools are available for the analysis of the glycome without derivatization, a process which is known to introduce issues such as differential loss of sialic acid and incomplete labeling. We have previously reported the use of ion chromatography-mass spectrometry (IC-MS) to analyze native sialylated and sulfated glycans. Here, we introduce improvements to IC column technology, enabling the separation of neutral glycans while maintaining charge separation capabilities. When implemented in an IC-MS workflow, this enables the structural characterization of a broad array of chemically distinct glycans. With the newly developed IC column and modified IC-MS instrumentation configuration, we qualitatively investigated O-glycome profiles in bovine fetuin and porcine gastric mucins. The improved chromatographic resolution in combination with high-resolution MS data present a powerful tool for glycan structural identification.

Highly selective recovery of medium chain carboxylates from co-fermented organic wastes using anion exchange with carbon dioxide expanded methanol desorption

The aim of this work was to recover a mixture of carboxylates ranging from 2 to 7 carbon atoms using a strong anion exchange resin, followed by desorption with CO₂-expanded methanol. Medium chain carboxylates hexanoate and heptanoate adsorbed better than acetate, and the corresponding medium chain carboxylic acids desorbed easier than acetic acid. Consequently, hexanoate and heptanoate were concentrated up to 14.6 and 20.7 times, respectively. These findings will enable effective separation and purification of the produced carboxylic acids. Notably, the presence of inorganic ions in the sample, such as chloride, decreased the adsorption affinity compared to a synthetic mixture only of carboxylates.

A simple procedure to obtain a medium-size oligogalacturonic acids fraction from orange peel and apple pomace wastes

Pectin oligosaccharides, which can be obtained from fruit wastes, have proven their potential as plant immune-system elicitors. Although the precise size of active species is still under investigation, medium size oligosaccharides have been reported as the most active. Three defined oligogalacturonic acid (OGAs) mixtures were produced from commercial pectin, orange peel and apple pomace residues. The methodology developed involves two sequential acid treatments followed by stepwise ethanol precipitation. Without the need of chromatographic separations, three different fractions were obtained. The fractions were analyzed by high performance anion exchange chromatography (HPAEC) and were completely characterized by mass spectrometry, showing that the small size, medium size and large size fractions contained OGAs of degree of polymerization 3 to 9, 6 to 18, and 16 to 55, respectively.

Sample Displacement Batch Chromatography of Proteins

In downstream processing, large-scale chromatography plays an important role. For its development, screening experiments followed by pilot-plant chromatography are mandatory steps. Here we describe fast, simple, and inexpensive methods for establishing a preparative chromatography for the separation of complex protein mixtures, based on sample displacement batch chromatography. The methods are demonstrated by anion-exchange chromatography of a human plasma protein fraction (Cohn IV-4), including the screening step and upscaling of the chromatography by a factor of one hundred. The results of the screening experiments and the preparative chromatography are monitored by SDS-PAGE electrophoresis. In summary, we provide a protocol, which should be easily adaptable for the chromatographic large-scale purification of other proteins, in the laboratory as well as in the manufacturing of biopharmaceuticals. These protocols cover the initial piloting steps for establishing a large-scale sample batch chromatography. The results from the piloting steps may also be applied for packed columns for performing simulated-moving-bed (SMB) chromatography rather than batch chromatography.

Pre-purification of diatom pigment protein complexes provides insight into the heterogeneity of FCP complexes

BACKGROUND

Although our knowledge about diatom photosynthesis has made huge progress over the last years, many aspects about their photosynthetic apparatus are still enigmatic. According to published data, the spatial organization as well as the biochemical composition of diatom thylakoid membranes is significantly different from that of higher plants.

RESULTS

In this study the pigment protein complexes of the diatom Thalassiosira pseudonana were isolated by anion exchange chromatography. A step gradient was used for the elution process, yielding five well-separated pigment protein fractions which were characterized in detail. The isolation of photosystem (PS) core complex fractions, which contained fucoxanthin chlorophyll proteins (FCPs), enabled the differentiation between different FCP complexes: FCP complexes which were more closely associated with the PSI and PSII core complexes and FCP complexes which built-up the peripheral antenna. Analysis by mass spectrometry showed that the FCP complexes associated with the PSI and PSII core complexes contained various Lhcf proteins, including Lhcf1, Lhcf2, Lhcf4, Lhcf5, Lhcf6, Lhcf8 and Lhcf9 proteins, while the peripheral FCP complexes were exclusively composed of Lhcf8 and Lhcf9. Lhcr proteins, namely Lhcr1, Lhcr3 and Lhcr14, were identified in fractions containing subunits of the PSI core complex. Lhcx1, Lhcx2 and Lhcx5 proteins co-eluted with PSII protein subunits. The first fraction contained an additional Lhcx protein, Lhcx6_1, and was furthermore characterized by high concentrations of photoprotective xanthophyll cycle pigments.

CONCLUSION

The results of the present study corroborate existing data, like the observation of a PSI-specific antenna complex in diatoms composed of Lhcr proteins. They complement other data, like e.g. on the protein composition of the 21 kDa FCP band or the Lhcf composition of FCPa and FCPb complexes. They also provide interesting new information, like the presence of the enzyme diadinoxanthin de-epoxidase in the Lhcx-containing PSII fraction, which might be relevant for the process of non-photochemical quenching. Finally, the high negative charge of the main FCP fraction may play a role in the organization and structure of the native diatom thylakoid membrane. Thus, the results present an important contribution to our understanding of the complex nature of the diatom antenna system.

Multi-epitope insert modulates solubility-based and chromatographic purification of human papilloma virus 16 L1-based vaccine without inhibiting virus-like particle assembly

The separation of heterogeneous protein mixtures has always been characterized by a trade-off between purity and yield. One way this issue has been addressed in the past is by recombinantly modifying protein to improve separations. Such modifications are mostly employed in the form of tags used specifically for affinity chromatography, though it is also possible to make changes to a protein that will have a sizeable impact on its hydrophobicity and charge/charge distribution. As such, it should also be possible to use protein tags to modulate phase separations and protein-resin binding kinetics when performing ion exchange chromatography. Here, we employed a three-step purification scheme on E. coli expressed, His-tagged, human papilloma virus 16 L1-based recombinant proteins (rHPV 16 L1) that consisted of an inclusion body (IB) wash step, a diethylaminoethyl (DEAE) anion exchange chromatography (AEX) step, and an immobilized metal affinity chromatography (IMAC) polishing step. Purification of the wild type rHPV 16 L1 protein (WT) was characterized by substantial losses during the IB wash but relatively high yield over the DEAE column. In contrast, purification of modified rHPV 16 L1, a chimeric version of the WT protein that had the last 34 amino acids replaced with an MHC class II multi-epitope insert derived from tetanus toxin and diphtheria toxin (WTΔC34-2TEp), was characterized by little to no losses in the IB wash but had a relatively low yield over the DEAE column. Since the fate of these proteins was to be used in vaccine formulations, it is important to note that the modifications made to the WTΔC34-2TEp protein had little to no effect on its ability to assemble into virus-like particles (VLPs). These results demonstrate that modifications of the WT protein via the recombinant insertion of immunofunctional polypeptides can modulate both phase-based separation and charge-based chromatographic processes. Additionally, incorporation of the specific, multi-epitope tag used in this study may prove to be beneficial in recombinant HPV vaccine development due to its potential to improve phase separation yield and vaccine immunogenicity without inhibiting VLP formation.

Retention and diffusion characteristics of oligonucleotides in a solid phase with polymer grafted anion-exchanger

In the chromatographic separation process of oligonucleotides (ONs), mechanistic understanding of their binding and diffusion processes is of significant importance to determine operating conditions in a fast and robust way. In this work, we determined the number of binding sites and the diffusivities of ONs in a polymer grafted anion exchange chromatography through linear gradient experiments (LGE) being carried out at selected four to five gradient slopes. Synthetic poly (T)s with length ranging from 3 to 90-mer were employed as a model of an antisense oligonucleotide with typical lengths of 10 - 30 bases. Comparison of the retention was also conducted between the grafted anion exchanger with a conventional ligand and an anion monolith disk. For the ONs up to 50 bases, the number of binding sites determined can be correlated with the length of ONs, and the grafted resin showed a better diffusion and narrower peak width compared to the nongrafted one. The retention behavior became similar for porous media when the longer ONs (> 50mer) were applied. The results obtained suggest that antisense ONs can be separated with grafted ligands without sacrificing mass transfer properties.

Purification of Lumbricus terrestris erythrocruorin (LtEc) with anion exchange chromatography

The naturally extracellular hemoglobin (erythrocruorin) of the Canadian nightcrawler, Lumbricus terrestris (LtEc), is a unique oxygen transport protein that may be an effective substitute for donated human blood. Indeed, this ultra-high molecular weight (~3.6 MDa) hemoglobin has already been shown to avoid the side effects associated with previous hemoglobin-based oxygen carriers and its high thermal stability (T_m = 56°C) and resistance to heme oxidation (k_ox = 0.04 hr^-1 × 10³ at 20°C) allow it to be stored for long periods of time without refrigeration. However, before it can be tested in human clinical trials, an effective and scalable purification process for LtEc must be developed. We have previously purified LtEc for animal studies with tangential flow filtration (TFF), which allows rapid and scalable purification of LtEc based on its relatively large size, but that type of size-based purification may not be able to specifically remove some impurities and high MW (>500 kDa) contaminants like endotoxin (MW = ~1-4 MDa). Anion exchange (AEX) and immobilized metal affinity chromatography (IMAC) are two purification methods that have been previously used to purify mammalian hemoglobins, but they have not yet been used to purify large invertebrate hemoglobins like LtEc. Therefore, the goal of this study was to determine if AEX and IMAC resins could successfully purify LtEc from crude earthworm homogenate, while also preserving its macromolecular structure and function. Both processes were able to produce purified LtEc with low levels of endotoxin, but IMAC purification induced significantly higher levels of heme oxidation and subunit dissociation than AEX. In addition, the IMAC process required an additional desalting step to enable LtEc binding. In contrast, AEX produced highly pure LtEc that was not dissociated. LtEc purified by AEX also exhibits similar oxygen binding characteristics (P₅₀ = 27.33 ± 1.82 mm Hg, n = 1.58 ± 0.17) to TFF-purified LtEc (P₅₀ = 28.84 ± 0.40 mm Hg, n = 1.93 ± 0.02). Therefore, AEX appears to be the optimal method for LtEc purification.

Bridging size and charge variants of a therapeutic monoclonal antibody by two-dimensional liquid chromatography

Monoclonal antibodies are heterogeneous in nature and may contain numerous variants with differences in size, charge, and hydrophobicity, which may impact clinical efficacy, immunogenicity, and safety. Characterization of antibody variants is necessary to build structure-function correlation and establish a proper control strategy. Isolation and enrichment of variants by conventional chromatographic peak fractionation is labor-intensive and time-consuming. The instability of fractions during isolation and subsequent characterization may also be a concern. Hence, it is desirable to analyze antibody variants in an online and real-time manner. Here we demonstrate a 2D-LC methodology - multiple heart-cutting IEC-SEC- as an investigational tool to facilitate a charge variant characterization study. Both IEC modes - anion exchange (AEX) and cation exchange (CEX) chromatography are discussed. Using this approach, direct bridging of size and charge variants of an antibody molecule was achieved without offline peak fractionation. It was observed that antibody aggregates elute late on both the AEX and CEX columns, presumably due to secondary hydrophobic interactions. Additionally, we overcame the solvent mismatch issue and developed a 2D SEC-IEC method to confirm the bridging results. This is the first reported SEC-IEC 2D-LC application for the characterization of antibody size and charge variants.

High-Grade Purification of Third-Generation HIV-Based Lentiviral Vectors by Anion Exchange Chromatography for Experimental Gene and Stem Cell Therapy Applications

Lentiviral vectors (LVs) have been increasingly used in clinical gene therapy applications particularly due to their efficient gene transfer ability, lack of interference from preexisting viral immunity, and long-term gene expression they provide. Purity of LVs is essential in in vivo applications, for a high therapeutic benefit with minimum toxicity. Accordingly, laboratory scale production of LVs frequently involves transient cotransfection of 293T cells with packaging and transfer plasmids in the presence of CaPO₄. After clearance of the cellular debris by low-speed centrifugation and filtration, lentivectors are usually concentrated by high-speed ultracentrifugation in sucrose cushion. Concentrated viral samples are then purified by anion exchange chromatography (AEX) after benzonase treatment to remove the residual cellular DNA. Here, we describe an improved practical method for LV purification using AEX, useful for experimental studies concerning gene and stem cell therapy.

Production of 191Pt from an iridium target by vertical beam irradiation and simultaneous alkali fusion

We have developed a new method for producing ¹⁹¹Pt from an iridium target. Alkali fusion of iridium was successfully performed using a vertical beam irradiation method and a mixed target of Ir and Na₂O₂, which resulted in easy dissolution of the irradiated iridium target. A trace amount of Pt^ⅣCl₆^2- was isolated from bulk Ir^ⅣCl₆^2- by solvent extraction and anion exchange chromatography. The production yield of ¹⁹¹Pt was 7.1 ± 0.4 (MBq/μA h, EOB) by proton irradiation at 30 MeV. The radioplatinum product (n.c.a.) was prepared at a radiochemical purity of 97% for Pt^ⅣCl₆^2-, and 95% for Pt^ⅡCl₄^2-, respectively.

Direct 3D printing of monolithic ion exchange adsorbers

Monolithic adsorbers with anion exchange (AEX) properties have been 3D printed in an easy one-step process, i.e. not requiring post-functionalization to introduce the AEX ligands. The adsorber, 3D printed using a commercial digital light processing (DLP) printer, was obtained by copolymerisation of a bifunctional monomer bearing a positively charged quaternary amine as well as an acrylate group, with the biocompatible crosslinker polyethylene glycol diacrylate (PEGDA). To increase the surface area, polyethylene glycol was introduced into the material formulation as pore forming agent. The influence of photoinitiator (Omnirad 819) and photoabsorber (Reactive Orange 16, RO16) concentration was investigated in order to optimize printing resolution, allowing to reliably 3D print features as small as 200 μm and of highly complex Schoen Gyroids. Protein binding was measured on AEX adsorbers with a range of ligand densities (0.00, 2.03, 2.60 and 3.18 mmol/mL) using bovine serum albumin (BSA) and c-phycocyanin (CPC) as model proteins. The highest equilibrium binding capacity was found for the material presenting the lowest ligand density analysed (2.03 mmol/mL), adsorbing 73.7 ± 5.9 mg/mL and 38.0 ± 2.2 mg/mL of BSA and CPC, respectively. This novel 3D printed material displayed binding capacities in par or even higher than commercially available chromatographic resins. We expect that the herein presented approach of using bifunctional monomers, bearing commonly used chromatography ligands, will help overcome the material limitations currently refraining 3D printing applications in separation sciences.

A rapid and effective method for purification of a heat-resistant lectin from potato (Solanum tuberosum) tubers

The potato lectin has been identified to consist of two chitin-binding modules, each containing twin hevein domains. Based on the thermotolerance of the hevein polypeptide, a simple, rapid, and effective protocol for the small-scale purification of the potato lectin has been developed in this study. The method involves only one anion exchange chromatographic step beyond the ammonium sulfate precipitation and the heating treatment. With this method, the potato lectin, a glycoprotein with molecular mass of approximately 60 kDa was found and purified to homogeneity with 9513.3 u/mg of specific hemagglutination (HA) activity in 76.8% yield. The homogeneity was confirmed by SDS-PAGE electrophoresis and reverse-phase HPLC analysis. The purified lectin was identified using MS-based peptide sequencing (MALDI-TOF/TOF) and showed a 100% Confidence Interval as being homologous to hevein domains in potato lectin. The periodic acid-Schiff staining and ferric-orcinol assay for pentose, as well as its HA activity inhibition by chitosan oligomers further confirmed the purified lectin as a potato chitin-binding lectin. It is noteworthy that the purified potato lectin exhibited heat resistance, by which, together with a short time precipitation by ammonium sulfate, more than 96% of the total proteins in the crude extract were removed. The lectin therefore was easily resolved from the other remining proteins on a DEAE-methyl polyacrylate column.

Characterization of IgM in Norwegian cleaner fish (lumpfish and wrasses)

The use of cleaner fish in Norwegian aquaculture has to a large extent been based on wild catches, but breeding of lumpfish and ballan wrasse is currently increasing. Due to disease problems and required vaccine development, tools to study immune responses and a better understanding of the immune system in these species is demanded. The present study comprises lumpfish (Cyclopterus lumpus) and five species of wrasses: Ballan wrasse (Labrus bergylta), rock cook (Centrolabrus exoletus), cuckoo wrasse (Labrus mixtus), corkwing wrasse (Symphodus melops), and goldsinny wrasse (Ctenolabrus rupestris). We present a comparison of the IgM sequences, phylogenetic relationship to other teleosts and characteristic features of IgM in the species studied. The lumpfish IgM heavy chain sequence was assembled from high throughput cDNA sequencing whereas the wrasse sequences were determined by molecular cloning. The secreted form of the IgM heavy chain from all species consisted of four constant Ig domains. IgM was purified from lumpfish and ballan wrasse sera by gel filtration followed by anion exchange chromatography, and polyclonal sera were produced against these proteins. Antisera against ballan wrasse IgM showed cross-reactivity to all analyzed species of wrasses, some cross-reactivity to lumpfish, very low reaction to salmon, and no reaction to cod. Anti- IgM sera against lumpfish cross-reacted to the light chain of all species studied. Wrasses and lumpfish IgM showed high binding affinities for protein A. IgM concentration in adult ballan wrasse (700-800 g) was measured by single radial immunodiffusion assay and found to be 13.4 mg/ml which is about 36% of the total protein concentration. The IgM concentration in lumpfish (600-3600 g) was estimated to 1-2.6 mg/ml, which corresponds to approximately 3% of the total protein concentration.

Design and Purification of Subunit Vaccines for Prevention of Clostridium difficile Infection

Clostridium difficile is a gram-positive bacterium responsible for a large proportion of nosocomial infections in the developed world. C. difficile secretes toxins A and B (TcdA and TcdB) and both toxins act synergistically to induce a spectrum of pathological responses in infected individuals ranging from pseudomembranous colitis to C. difficile-associated diarrhea. Toxins A and B have been actively investigated as components of prophylactic vaccine as well as targets for therapeutic intervention with antibodies. Expression of such toxins by recombinant technology is often difficult and may require special handling and adherence to strict safety regulations during the manufacturing process due to the inherent toxicity of the proteins. Both toxins are large proteins (308 kDa and 270 kDa, respectively) and contain distinct domains mediating cell attachment, cellular translocation, and enzymatic (glucosidase) activity. Here we describe methods to produce fragments of Toxin B for their subsequent evaluation as components of experimental C. difficile vaccines. Methods presented include selection of fragments encompassing distinct functional regions of Toxin B, purification methods to yield high quality proteins, and analytical evaluation techniques. The approach presented focuses on Toxin B but could be applied to the other component, Toxin A, and/or to any difficult to express or toxic protein.

Dataset on protein composition of a human plasma sub-proteome able to modulate the Dengue 2 virus infection in Huh 7.5 cells

The four serotypes of dengue virus (DENV1-4) are the causal agents of the emerging disease Dengue Fever and its severe forms. DENV is inoculated into human blood through a mosquito bite. Thus, plasma is an important media for DENV dissemination in infected persons and several important interactions should take place for the virus with human plasma proteins that strongly influence or may determine the course of the infection. This dataset contains 239 proteins identified in the elution fractions of human plasma subjected to DE-52 anion exchange chromatography. Data on DENV2 infection of Huh 7.5 cells in presence of the human plasma fraction is also presented.

Expression and characterization of a cytosolic glucose 6 phosphate dehydrogenase isoform from barley (Hordeum vulgare) roots

In plant cells, glucose 6 phosphate dehydrogenase (G6PDH-EC 1.1.1.49) regulates the oxidative pentose phosphate pathway (OPPP), a metabolic route involved in the production of NADPH for various biosynthetic processes and stress response. In this study, we report the overexpression of a cytosolic G6PDH isoform from barley (Hordeum vulgare) roots in bacteria, and the biochemical characterization of the purified recombinant enzyme (HvCy-G6PDH). A full-length cDNA coding for a cytosolic isoform of G6PDH was isolated, and the sequence was cloned into pET3d vector; the protein was overexpressed in Escherichia coli BL21 (DE3) and purified by anion exchange and affinity chromatography. The kinetic properties were calculated: the recombinant HvCy-G6PDH showed KMs and KINADPH comparable to those observed for the enzyme purified from barley roots; moreover, the analysis of NADPH inhibition suggested a competitive mechanism. Therefore, this enzyme could be utilised for the structural and regulatory characterization of this isoform in higher plants.

Expression, purification and characterization of inactive and active forms of ERK2 from insect expression system

Extracellular signal-regulated kinase 2 (ERK2) is a serine/threonine protein kinase involved in many cellular programs, such as cell proliferation, differentiation, motility and programed cell-death. It is therefore considered an important target in the treatment of cancer. In an effort to support biochemical screening and small molecule drug discovery, we established a robust system to generate both inactive and active forms of ERK2 using insect expression system. We report here, for the first time, that inactive ERK2 can be expressed and purified with 100% homogeneity in the unphosphorylated form using insect system. This resulted in a significant 20-fold yield improvement compared to that previously reported using bacterial expression system. We also report a newly developed system to generate active ERK2 in insect cells through in vivo co-expression with a constitutively active MEK1 (S218D S222D). Isolated active ERK2 was confirmed to be doubly phosphorylated at the correct sites, T185 and Y187, in the activation loop of ERK2. Both ERK2 forms, inactive and active, were well characterized by biochemical activity assay for their kinase function. Inactive and active ERK2 were the two key reagents that enabled successful high through-put biochemical assay screen and structural drug discovery studies.

Chromatographic isolation of the functionally active MutS protein covalently linked to deoxyribonucleic acid

DNA metabolism is based on formation of different DNA-protein complexes which can adopt various conformations. To characterize functioning of such complexes, one needs a solution-based technique which allows fixing a complex in a certain transient conformation. The crosslinking approach is a popular tool for such studies. However, it is under debate if the protein components retain their natural activities in the resulting crosslinked complexes. In the present work we demonstrate the possibility of obtaining pure DNA conjugate with functionally active protein using as example MutS protein from Escherichia coli mismatch repair system. A conjugate of a chemically modified mismatch-containing DNA duplex with MutS is fixed by thiol-disulfide exchange reaction. To perform a reliable test of the protein activity in the conjugate, such conjugate must be thoroughly separated from the uncrosslinked protein and DNA prior to the test. In the present work, we employ anion exchange chromatography for this purpose for the first time and demonstrate this technique to be optimal for the conjugate purification. The activity test is a FRET-based detection of DNA unbending. We show experimentally that MutS in the conjugate retains its ability to unbend DNA in response to ATP addition and find out for the first time that the DNA unbending rate increases with increasing ATP concentration. Since the crosslinked complexes contain active MutS protein, they can be used in further experiments to investigate MutS interactions with other proteins of the mismatch repair system.

Preparation of high purity egg phosvitin using anion exchange chromatography

Egg yolk phosvitin serves as a warehouse to provide metal ions for embryo development. It is significant for mineral metabolism study and also of great potential to be developed into functional foods with mineral absorption promoting ability. In this study, phosvitin was first extracted from yolk granules using 10% NaCl, dialysed and then adjusted to various pHs to remove impurities. The purity of phosvitin extracts was increased from 54.5% to 63.7% at decreasing pH from 8.0 to 5.5, and started to decrease afterwards. Both the yield and recovery were significantly decreased at decreasing pHs, especially at pHs close to its pI (pH 4.0), indicating the occurrence of co-precipitation of phosvitin with HDL. The extract prepared at pH 8.0 showed the highest recovery of 82.7%; its purity was increased from 54.5% to 97.1% by anion exchange chromatography, with a recovery of 42.0%. This simple method could be scaled up for industrial production.

A purification system for 64Cu produced by a biomedical cyclotron for antibody PET imaging

Ion exchange is a simple and efficient method for separating no-carrier-added ⁶⁴Cu from an irradiated Ni target. We developed a semi-automated two-round ⁶⁴Cu separation system equipped with a strong-base anion exchange resin column. We first verified the efficiency of the system using a non-radioactive substitute consisting of 25 mg of Ni and 127 ng of Cu, and confirmed that Cu was completely eluted at the second round of the separation step. After the bombardment, separation of ⁶⁴Cu from the Ni target was achieved with high radiochemical purity. ⁶⁴Cu produced and separated in this study had an extremely low level of Ni impurity. It could be used for labeling monoclonal antibodies for antibody positron emission tomography imaging and synthesizing radiopharmaceuticals.

Cell-Based Microscale Isolation of Glycoaminoglycans for Glycomics Study

Glycomics research requires the isolation of glycans from cells for structural characterization and functional studies of the glycans. A method for cell-based microscale isolation and quantification of highly sulfated, moderately sulfated, and nonsulfated glycosaminoglycans (GAGs) was developed using Chinese hamster ovary (CHO) cells. This microscale isolation relies on a mini-strong anion exchange spin column eluted stepwise with different concentrations of sodium chloride solution. Hyaluronic acid, chondroitin sulfate, and heparin were used to optimize the isolation of the endogenous glycosaminoglycans in CHO cells. This method can also be used to determine the presence of nonsulfated GAGs including heparosan, hyaluronic acid, and nonsulfated chondroitin.