Weak partitioning chromatography for anion exchange purification of monoclonal antibodies

Weak partitioning chromatography (WPC) is an isocratic chromatographic protein separation method performed under mobile phase conditions where a significant amount of the product protein binds to the resin, well in excess of typical flowthrough operations. The more stringent load and wash conditions lead to improved removal of more tightly binding impurities, although at the cost of a reduction in step yield. The step yield can be restored by extending the column load and incorporating a short wash at the end of the load stage. The use of WPC with anion exchange resins enables a two-column cGMP purification platform to be used for many different mAbs. The operating window for WPC can be easily established using high throughput batch-binding screens. Under conditions that favor very strong product binding, competitive effects from product binding can give rise to a reduction in column loading capacity. Robust performance of WPC anion exchange chromatography has been demonstrated in multiple cGMP mAb purification processes. Excellent clearance of host cell proteins, leached Protein A, DNA, high molecular weight species, and model virus has been achieved.     

High performance anion exchange chromatography of reduced oligosaccharides from sialomucins

High performance anion exchange chromatography on pellicular ion exchange resins under high pH conditions with detection of sugars using a pulsed amperometric detector has been developed as a method for the separation and analysis of reduced oligosaccharides liberated from mucins by alkaline borohydride treatment. Ovine, bovine and porcine submaxillary mucins were used as models to develop the method. Although neutral reduced di-to tetraoligosaccharides were poorly retained on the column, a variety of sialylated reduced oligosaccharides could be separated efficiently. Treatment of the samples with sialidase and rechromatography identified the sialylated compounds in the elution profile. A striking finding was the greatly delayed elution times given byN-glycolylneuraminic acid containing compounds in comparison with the correspondingN-acetylneuraminic acid containing analogues. The elution profiles for the product from the mucins closely corresponded to those expected for the major oligosaccharides from these mucins. The procedures described will be useful for analysing sialomucins on a microscale without resorting to radiolabelling procedures.     

Combination of size-exclusion chromatography and ion exchange adsorption for improving the proteomic analysis of plasma-derived extracellular vesicles

Extracellular vesicles (EVs) are lipid membrane vesicles released by live cells that carry a variety of biomolecules, including nucleic acids, lipids, and proteins. Recently, proteins in plasma-derived EVs have emerged as novel biomarkers with essential functions in the diagnosis and prognosis of human diseases. However, the current methods of isolating EVs from plasma often lead to coisolated impurities in biological fluids. Therefore, before performing any research protocol, the process of extracting EVs from plasma for proteomic analysis must be optimized. In this study, two EV isolation strategies, size exclusion chromatography (SEC) and SEC combined with ion exchange adsorption (SEC + IEA), were compared in terms of the purity and quantity of protein in EVs. Our results demonstrated that, compared to single-step SEC, SEC combined with IEA could produce plasma-derived EVs with a higher purity by decreasing the abundance of lipoprotein. Additionally, with MS analysis, we demonstrated that the combination approach maintained the stability and improved the purity of EVs in many plasma samples. Furthermore, by combining SEC with IEA, more cancer-associated proteins were detected in the plasma of various cancer samples.     

Structural and performance characteristics of representative anion exchange resins used for weak partitioning chromatography

Weak partitioning chromatography (WPC) has been proposed for the purification of monoclonal antibodies using an anion exchange (AEX) resin to simultaneously remove both acidic and basic protein impurities. Despite potential advantages, the relationship between resin structure and WPC performance has not been evaluated systematically. In this work, we determine the structure of representative AEX resins (Fractogel® EMD TMAE HiCap, Q Sepharose FF, and POROS 50 HQ) using transmission electron microscopy and inverse size exclusion chromatography and characterize protein interactions while operating these resins under WPC conditions using two mAb monomers, a mAb dimer, mAb multimers, and BSA as model products and impurities. We determine the isocratic elution behavior of the weakly bound monomer and dimer species and the adsorptive and mass transfer properties of the strongly bound multimers and BSA by confocal laser scanning microscopy. The results show that for each resin, using the product K_p value as guidance, salt, and pH conditions can be found where mAb multimers and BSA are simultaneously removed. Isocratic elution and adsorption mechanisms are, however, different for each resin and for the different components. Under WPC conditions, the Fractogel resin exhibited very slow diffusion of both mAb monomer and dimer species but fast adsorption for both mAb multimers and BSA with high capacity for BSA, while the Sepharose resin, because of its small pore size, was unable to effectively remove mAb multimers. The POROS resin was instead able to bind both multimers and BSA effectively, while exhibiting a greater resolution of mAb monomer and dimer species. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:425–434, 2017     

需钠弧菌外膜囊泡的蛋白质组分析与异源蛋白的递送

[背景] 需钠弧菌（Vibrio natriegens）是一种快速生长的革兰氏阴性菌,作为一种新兴工具在生物技术领域有重要的应用潜力。此前的研究主要集中在开发利用V. natriegens成为体内外重组蛋白生产的工具。然而,许多支持细菌进行快速生长和蛋白质生产的生理活动大部分仍未确定。外膜囊泡（Outer Membrane Vesicle,OMV）是由革兰氏阴性细菌普遍产生的一种球形小泡,其不仅具有重要的功能,而且还可以作为一种应用于疫苗治疗的高效运载工具。[目的] 表征指数生长期OMV的蛋白质组并利用OMV进行异源蛋白的递送。[方法] 使用透射电镜、动态光散射和质谱学的方法,观察OMV的形态及粒径分布并鉴定蛋白组成。以超折叠绿色荧光蛋白（Superfolded Green Fluorescent Protein,sfGFP）作为货物蛋白来确定OMV蛋白载体。[结果] 从细菌培养的指数期中期和末期分别提取的OMV中鉴定到了288个和317个蛋白。这些蛋白分属不同的功能组,包括ABC转运蛋白、鞭毛、双组分系统。相比之下,同时鉴定了全细胞样品,其在指数期中期和末期分别含有1 480个和1 565个蛋白。我们筛选OMV的蛋白作为候选载体发现了一种属于OmpA家族的蛋白（命名为OmpA24）,其能够将sfGFP以融合货物蛋白的形式运载到OMV中。[结论] 首次证实V. natriegens能够在指数生长期产生OMV,并展示了第一个不同生长时期OMV和全细胞的蛋白质组鉴定结果。OmpA24是将外源融合货物蛋白呈递到OMV中的有前景的载体。本研究有助于促进V. natriegens在蛋白表达和OMV介导的分泌中的应用。     

细菌吸附及转运芳香族化合物的研究进展

芳香族化合物是一类具有苯环结构的有机物,它们结构稳定,不易分解,并可通过食物链进行生物富集和生物放大,对生态环境及人类健康造成极大危害。细菌具有超强的分解代谢能力,能降解多环芳烃(polycyclic aromatic hydrocarbons, PAHs)等多种难降解芳香族污染物。吸附和转运是细菌进行芳香族化合物细胞内代谢的前提。虽然芳香族化合物的细菌降解已取得较为显著的研究进展,但吸附和转运机理仍不甚清楚。本文讨论了细菌对芳香族化合物的吸附有积极作用的细胞表面疏水性、生物被膜形成和细菌趋化性等影响因素,总结了FadL家族、TonB依赖性受体蛋白、OmpW家族等外膜转运系统和主要协同转运蛋白超家族(major facilitator superfamily, MFS)转运体、ATP结合盒(ATP-binding cassette, ABC)转运蛋白等内膜转运系统对该类化合物跨膜运输作用,并对跨膜转运机制进行了讨论和阐述,旨在为芳香族污染物的防控和治理提供一定理论参考。     

Isolation and purification of lactoferrin and immunoglobulin G from bovine colostrum with serial cation-anion exchange chromatography

High-value dairy proteins such as lactoferrin (LF) and immunoglobulin (IgG) were separated from bovine colostrum. The whey was initially adjusted to pH 6.8 with 1 mol/L NaOH and then went through centrifugation, precipitation, and filtration to eliminate the fat and caseins in bovine colostrum. The treated whey was further ultra-filtrated to partially remove both other proteins and carbohydrates under 50 kD molecular weight. Then the ultra-filtrated whey was passed through cation and anion exchange columns in series. The LF and IgG were adsorbed on cation and anion exchanger, respectively, due to their different pI. Both the cation and anion exchange columns were washed with de-ionized water followed by successive elution with sodium chloride solutions of increasing molarities (0.27 and 0.85 mol/L; 17 and 51 mmol/L) in a stepwise manner, respectively. After desalted, the elution was freeze-dried. Finally, the LF and IgG with respective purities of 95.0% and 96.6% were obtained.     

Production,optimization, purification,characterization, and anti-cancer application of extracellular L-glutaminase produced from the marine bacterial isolate

Abstract

L-glutaminase from bacterial sources has been proven to be effective and economical agents in cancer therapy, food industry and high-value chemicals like threonine. In the present study, a newly isolated bacterial strain was potentially producing extracellular L-glutaminase, it identified as Bacillus subtilis OHEM11 (MK389501) using the 16S rRNA gene. L-glutaminase production optimized and the optimum factors for production under submerged fermentation were at pH 6.5–7.0 and 35?°C after 28?hr using rhamnose and glutamine as carbon and nitrogen sources, respectively, while bagasse was the best inducer for the production under solid-state fermentation. Ethanol precipitation and ion-exchange chromatography using QFF are the purification steps. L-glutaminase was purified to 2-fold with specific activity 89.78?U/mg and its molecular weight about 54.8?kDa with the alkaline property of the enzyme makes it clear having carcinostatic property; maximum enzyme activity at pH 8.2 and 40?°C and retained about 90% activity for 1?hr. The cytotoxicity effect of L-glutaminase indicated a significant safety on Vero cells with high anticancer activity against NFS-60, HepG-2, and MCF-7 cancer cell lines. The outcomes demonstrated that L-glutaminase could be applied in many biotechnological applications such as pharmaceutical and food processing.     

The effect of protein a cycle number on the performance and lifetime of an anion exchange polishing step

Most mAb platform purification processes consist of an affinity capture step followed by one or two polishing steps. An understanding of the performance linkages between the unit operations can lead to robust manufacturing processes. In this study, a weak‐partitioning anion‐exchange chromatography polishing step used in a mAb purification process was characterized through high‐throughput screening (HTS) experiments, small‐scale experiments including a cycling study performed on qualified scale‐down models, and large‐scale manufacturing runs. When material from a Protein A column that had been cycled <10× was loaded on the AEX resin, early breakthrough of impurities and premature loss of capacity was observed. As the cycle number on the Protein A resin increased, the capacity of the subsequent AEX step increased. Different control strategies were considered for preventing impurity breakthrough and improving AEX resin lifetimes. Depth filtration of the Protein A peak pool significantly improved the AEX resin capacity, robustness, and lifetime. Further, the turbidity of the Protein A pool has the potential for use as an in‐process control parameter for monitoring the performance of the AEX step. Biotechnol. Bioeng. 2013; 110: 1142–1152. © 2012 Wiley Periodicals, Inc.     

VAP-A and its binding partner CERT drive biogenesis of RNA-containing extracellular vesicles at ER membrane contact sites

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Comparison of theN-glycoloylneuraminic andN-acetylneuraminic acid content of platelets and their precursors using high performance anion exchange chromatography

N-Acetylneuraminic acid (Neu5Ac) andN-glycoloylneuraminic acid (Neu5Gc) are distributed widely in nature. Using a Carbopac PA-1 anion exchange column, we have determined the ratios of Neu5Ac and Neu5Gc in hydrolysates of platelets and their precursors: a rat promegakaryoblastic (RPM) cell line and a human megakaryoblastic leukemia cell line (MEG-01). The ratio of Neu5Gc:Neu5Ac in cultured RPM cells is 16:1, whereas in platelet rich plasma and cultured MEG-01 cells it is 1:38 and 1:28, respectively. The nature of these sialic acids from RPM cells was verified using thin layer chromatography and liquid secondary ion mass spectrometry. The relevance of increased Neu5Gc levels in early stages of development is discussed.Abbreviations Neu5Ac N-acetylneuraminic acid - Neu5Gc N-glycoloylneuraminic acid - RPM rat promegakaryoblast - MEG-01 human megakaryoblastic leukaemia cell line - PAD pulsed amperometric detection - WGA wheat germ agglutinin - FCS foetal calf serum - PPEADF phosphatidylethanolamine dipalmitoyl - LSIMS liquid secondary ion mass spectrometry - HPAEC high performance anion exchange chromatography - TBA thiobarbituric acid     

Expression of caltrin in the baculovirus system and its purification in high yield and purity by cobalt (II) affinity chromatography

Direct protein extraction from animals is the only approach available to obtain caltrin, calcium transport inhibitor. Here we report the expression and purification of caltrin, previously shown to hinder the influx of calcium into epididymal spermatozoa. Cloning of the caltrin gene into the pCDNA3.1 V5/His-TOPO vector and the subsequent ligation of the caltrin-His sequence into the transfer vector pBacPAK9 allowed the expression of recombinant caltrin using the baculovirus expression vector system (BEVS). Recombinant His-tagged caltrin was purified utilising both nickel (II)-nitrilotriacetic acid (Ni(2+)-NTA) and cobalt (II)-carboxymethylaspartate (Co(2+)-CmAsp) immobilised metal affinity chromatography (IMAC). Using the BEVS, caltrin-His was identified in the supernatant and in the cell lysate, suggesting that caltrin is a secreted protein. Based on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot results, purified recombinant caltrin-His was ascertained to be approximately 14.5kDa. Purification under the Co(2+) system yielded significantly purer protein samples when compared to the Ni(2+) system. Furthermore, Co(2+) was observed to bind the recombinant caltrin-His protein with higher efficiency and specificity and to yield a higher total protein concentration. Collectively, our results indicate that the Co(2+) system would be a better approach for purifying caltrin-His proteins than the Ni(2+).     

Refolding and purification of recombinant human (Pro)renin receptor from Escherichia coli by ion exchange chromatography

Purification of the recombinant human renin receptor (rhRnR) is a major aspect of its biological or biophysical analysis, as well as structural research. A simple and efficient method for the refolding and purification of rhRnR expressed in Escherichia coli with weak anion‐exchange chromatography (WAX) was presented in this work. The solution containing denatured rhRnR in 8.0 mol/L urea extracted from the inclusion bodies was directly injected into the WAX column. The aggregation was prevented and the soluble form of renatured rhRnR in aqueous solution was obtained after desorption from the column. Effects of the extracting solutions, the pH values and urea concentrations in the mobile phase, as well as the sample size on the refolding and purification of rhRnR were investigated, indicating that the above mentioned factors had remarkable influences on the efficiency of refolding, purification and mass recovery of rhRnR. Under the optimal conditions, rhRnR was successfully refolded and purified simultaneously by WAX in one step within only 30 min. The result was satisfactory with mass recovery of 71.8% and purity of 94.8%, which was further tested by western blotting. The specific binding of the purified rhRnR to recombinant human renin was also determined using surface plasmon resonance (SPR). The association constant of rhRnR to recombinant human renin was calculated to be 3.25 × 10⁸ L/mol, which demonstrated that rhRnR was already renatured and simultaneously purified in one step using WAX. All of the above demonstrate that protein folding liquid chromatography (PFLC) should be a powerful tool for the purification and renaturation of rhRnR. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:864–871, 2014     

Pentavalent outer membrane vesicles of Vibrio cholerae induce adaptive immune response and protective efficacy in both adult and passive suckling mice models

Recently, we demonstrated oral immunizations with single serotype outer membrane vesicles of Vibrio cholerae induced serogroup specific protective immunity in the RITARD model. In our present study, we advanced our research by formulating multi-serotype outer membrane vesicles, mixing the OMVs of five virulent V. cholerae strains. Four doses of oral immunization with cholera pentavalent outer membrane vesicles (CPMVs) induced V. cholerae specific B and T cell responses. CPMVs-immunized mice generated long lasting serum IgG, IgA, IgM as well as mucosal sIgA and also elicited a higher percentage of CD4+ T cell distribution in spleen. Our study revealed that in vitro CPMVs-activated dendritic cells were secreting T cell polarizing cytokines, IL-12p40, IL-4, IL-6 and IL-1β. Moreover, purified splenic CD4+ T cells of immunized mice also secreted IL-4, IL-13 and IL-17 cytokines, indicating the initiation of Th2 and Th17 cell mediated immune responses. CPMVs immunized adult female mice and their offspring were significantly protected from heterologous challenge with wild type V. cholerae. CPMVs could be exploited for the development of a novel non-living vaccine against circulating cholera in near future.     

High yield purification and first structural characterization of the full‐length bacterial toxin CNF1

The Cytotoxic Necrotizing Factor 1 (CNF1) is a bacterial toxin secreted by certain Escherichia coli strains causing severe pathologies, making it a protein of pivotal interest in toxicology. In parallel, the CNF1 capability to influence important neuronal processes, like neuronal arborization, astrocytic support, and efficient ATP production, has been efficiently used in the treatment of neurological diseases, making it a promising candidate for therapy. Nonetheless, there are still some unsolved issues about the CNF1 mechanism of action and structuration probably caused by the difficulty to achieve sufficient amounts of the full‐length protein for further studies. Here, we propose an efficient strategy for the production and purification of this toxin as a his‐tagged recombinant protein from E. coli extracts (CNF1‐H8). CNF1‐H8 was expressed at the low temperature of 15°C to diminish its characteristic degradation. Then, its purification was achieved using an immobilized metal affinity chromatography (IMAC) and a size exclusion chromatography so as to collect up to 8 mg of protein per liter of culture in a highly pure form. Routine dynamic light scattering (DLS) experiments showed that the recombinant protein preparations were homogeneous and preserved this state for a long time. Furthermore, CNF1‐H8 functionality was confirmed by testing its activity on purified RhoA and on HEp‐2 cultured cells. Finally, a first structural characterization of the full‐length toxin in terms of secondary structure and thermal stability was performed by circular dichroism (CD). These studies demonstrate that our system can be used to produce high quantities of pure recombinant protein for a detailed structural analysis. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:150–159, 2018