Preparation of a modified crosslinked chitosan/polyvinyl alcohol blended affinity membrane for purification of His-tagged protein

Affinity purification/immobilization of poly histidine-tagged proteins by nickel-functionalized porous chitosan membranes

Although immobilized metal ion affinity chromatography (IMAC) is one of the most effective methods for purifying his-tagged proteins, it has limitations such as expensive commercial resins and non-specific binding of unwanted proteins to the nickel immobilized on the resin. In this study, biocompatible chitosan and porous chitosan membranes as alternative resins were synthesized for protein immobilization and purification, but finally porous chitosan membrane was selected due to its higher porosity and consequently higher nickel adsorption. Once the membrane was functionalized with nickel ions and its metal adsorption confirmed by EDS and ICP methods, it was used to immobilize and purify recombinant β-NGF as a protein model with his-tag tail in batch-fashion. Protein binding and purification were also approved by FTIR and UV-Vis spectroscopy and SDS-PAGE technique. Our results indicated that the protein of interest could bind to the nickel-functionalized porous chitosan membrane with high efficiency at pH=7. Furthermore, for protein purification, the pH value of 6 and an imidazole concentration of 750 mM were suggested for the final elution buffer. In conclusion, nickel-functionalized porous chitosan membrane could be a suitable alternative to IMAC for low cost and specific protein immobilization and purification.

One-Step Purification and Immobilization of Glycosyltransferase with Zn-Ni MOF for the Synthesis of Rare Ginsenoside Rh2

Uridine diphosphate (UDP)-glucosyltransferases (UGTs) have received increasing attention in the field of ginsenoside Rh2 conversion. By harnessing the metal chelation between transition metal ions and imidazole groups present on His-tagged enzymes, a specific immobilization of the enzyme within metal-organic frameworks (MOFs) is achieved. This innovative approach not only enhances the stability and reusability of the enzyme but also enables one-step purification and immobilization. Consequently, the need for purifying crude enzyme solutions is effectively circumvented, resulting in significant cost savings during experimentation. The use of immobilized enzymes in catalytic reactions has shown great potential for achieving higher conversion rates of ginsenoside Rh2. In this study, highly stable mesoporous Zn-Ni MOF materials were synthesized at 150 °C by a solvothermal method. The UGT immobilized on the Zn-Ni MOF (referred to as UGT@Zn-Ni MOF) exhibited superior pH adaptability and thermal stability, retaining approximately 76% of its initial activity even after undergoing 7 cycles. Furthermore, the relative activity of the immobilized enzyme remained at an impressive 80.22% even after 45 days of storage. The strong specific adsorption property of Zn-Ni MOF on His-tagged UGT was confirmed through analysis using polyacrylamide gel electrophoresis. UGT@Zn-Ni MOF was used to catalyze the conversion reaction, and the concentration of rare ginsenoside Rh2 was generated at 3.15 μg/mL. The results showed that Zn-Ni MOF is a material that can efficiently purify and immobilize His-tagged enzyme in one step and has great potential for industrial applications in enzyme purification and ginsenoside synthesis.

Ni(II) functionalized polyhedral oligomeric silsesquioxane based capillary monolith for purification of histidine-tagged proteins by immobilized metal affinity micro-chromatography

A new capillary monolithic stationary phase was synthesized for the purification of histidine tagged proteins by immobilized metal affinity micro-chromatography (μ-IMAC). For this purpose, mercaptosuccinic acid (MSA) linked-polyhedral oligomeric silsesquioxane [MSA@poly(POSS-MA)] monolith 300 μm in diameter was obtained by thiol-methacrylate polymerization using methacryl substituted-polyhedral oligomeric silsesquioxane (POSS-MA) and MSA as the thiol functionalized agent in a fused silica capillary tubing. Ni(II) cations were immobilized onto the porous monolith via metal-chelate complex formation with double carboxyl functionality of bound MSA segments. μ-IMAC separations aiming the purification of histidine tagged-green fluorescent protein (His-GFP) from Escherichia coli extract were carried out on Ni(II)@MSA functionalized-poly(POSS-MA) [Ni(II)@MSA@poly(POSS-MA)] capillary monolith. His-GFP was succesfully isolated by μ-IMAC on Ni(II)@MSA@poly(POSS-MA) capillary monolith with the isolation yield of 85 % and the purity of 92 % from E. coli extract. Higher His-GFP isolation yields were obtained with lower His-GFP feed concentrations and lower feed flow rates. The monolith was used for consecutive His-GFP purifications with a tolerable decrease in equilibrium His-GFP adsorption over five runs.

Immobilization of Recombinant Endoglucanase (CelA) from Clostridium thermocellum on Modified Regenerated Cellulose Membrane

Cellulases are being widely employed in lignocellulosic biorefineries for the sustainable production of value-added bioproducts. However, the high production cost, sensitivity, and non-reusability of free cellulase enzymes impede their commercial applications. Enzyme immobilization seems to be a potential approach to address the aforesaid complications. The current study aims at the production of recombinant endoglucanase (CelA) originated from the cellulosome of Clostridium thermocellum in Escherichia coli (E. coli), followed by immobilization using modified regenerated cellulose (RC) membranes. The surface modification of RC membranes was performed in two different ways: one to generate the immobilized metal ion affinity membranes RC-EPI-IDA-Co2+ (IMAMs) for coordination coupling and another to develop aldehyde functional group membranes RC-EPI-DA-GA (AMs) for covalent bonding. For the preparation of IMAMs, cobalt ions expressed the highest affinity effect compared to other metal ions. Both enzyme-immobilized membranes exhibited better thermal stability and maintained an improved relative activity at higher temperatures (50–90 °C). In the storage analysis, 80% relative activity was retained after 15 days at 4 °C. Furthermore, the IMAM- and AM-immobilized CelA retained 63% and 53% relative activity, respectively, after being reused five times. As to the purification effect during immobilization, IMAMs showed a better purification fold of 3.19 than AMs. The IMAMs also displayed better kinetic parameters, with a higher Vmax of 15.57 U mg−1 and a lower Km of 36.14 mg mL−1, than those of AMs. The IMAMs were regenerated via treatment with stripping buffer and reloaded with enzymes and displayed almost 100% activity, the same as free enzymes, up to 5 cycles of regeneration.

Molecularly Imprinted Affinity Membrane: A Review

A molecularly imprinted affinity membrane (MIAM) can perform separation with high selectivity due to its unique molecular recognition introduced from the molecular-printing technique. In this way, a MIAM is able to separate a specific or targeted molecule from a mixture. In addition, it is possible to achieve high selectivity while maintaining membrane permeability. Various methods have been developed to produce a MIAM with high selectivity and productivity, with their respective advantages and disadvantages. In this paper, the MIAM is reviewed comprehensively, from the fundamentals of the affinity membrane to its applications. First, the development of a MIAM and various preparation methods are presented. Then, applications of MIAMs in sensor, metal ion separation, and organic compound separation are discussed. The last part of the review discusses the outlook of MIAMs for future development.

Aqueous Strippable Polymer Coating for Highly Efficient Primary Radioactive Uranium Decontamination with Versatility on Diversified Surface

The decontamination of radioactive materials on the surfaces of nuclear facilities has generated large quantities of waste from the rapid development of the nuclear industry, posing a potential threat globally. Strippable coating has been employed for some time to remove radioactive contamination due to its high performance and removability, flexibility, and compatibility with various substrates. Herein, an aqueous strippable coating based on an adsorbent/polyvinyl alcohol (PVA) polymer was developed to remove radioactive uranium from stainless-steel surfaces that showed greater decontamination than that of DeconGel, with an efficiency of 87.2% for 5 g/L uranium and 95.5% for 22.5 g/L uranium, along with a high repeatability and better mechanical properties. Furthermore, the prepared coating was versatile and could be applied to a range of substrate surfaces (lacquered, aluminum, glass, plastic, and ceramic), with outstanding performance ranging from 79.2 to 95.4% for 1 g/L uranium. The prepared coating could also be applied through brushing or spraying to horizontal or vertical substrates. The exceptional performance could be due to the synergistic effect of the introduction of ethylene diamine tetra-acetic acid disodium salt (EDTA-2Na) as a chelating agent and the nano-adsorbent CaCO₃/TiO₂.

Recent Developments of Liquid Chromatography Stationary Phases for Compound Separation: From Proteins to Small Organic Compounds

Compound separation plays a key role in producing and analyzing chemical compounds. Various methods are offered to obtain high-quality separation results. Liquid chromatography is one of the most common tools used in compound separation across length scales, from larger biomacromolecules to smaller organic compounds. Liquid chromatography also allows ease of modification, the ability to combine compatible mobile and stationary phases, the ability to conduct qualitative and quantitative analyses, and the ability to concentrate samples. Notably, the main feature of a liquid chromatography setup is the stationary phase. The stationary phase directly interacts with the samples via various basic mode of interactions based on affinity, size, and electrostatic interactions. Different interactions between compounds and the stationary phase will eventually result in compound separation. Recent years have witnessed the development of stationary phases to increase binding selectivity, tunability, and reusability. To demonstrate the use of liquid chromatography across length scales of target molecules, this review discusses the recent development of stationary phases for separating macromolecule proteins and small organic compounds, such as small chiral molecules and polycyclic aromatic hydrocarbons (PAHs).

Recent trends in sorbents for bioaffinity chromatography

Isolation or enrichment of biological molecules from complex biological samples is mostly a prerequisite in proteomics, genomics, and glycomics. Different techniques have been used to advance the efficiency of the purification of biological molecules. Bioaffinity chromatography is one of the most powerful technique that plays an important role in the isolation of target biological molecules by the specific interactions with ligands that are immobilized on different support materials. This review examines the recent developments in bioaffinity chromatography particularly over the past 5 years in the literature. Also properties of supports, immobilization techniques, types of binding agents, and methods used in bioaffinity chromatography applications are summarized.