Tag-mediated single-step purification and immobilization of recombinant proteins toward protein-engineered advanced materials

Immobilizing the Endogenous 5-Hydroxytryptamine Transporter by Ligand-Directed and Proximity-Catalyzed Acyl Imidazole Chemistry for Affinity Chromatographic Analysis

The sensitivity, selectivity, and accuracy of immobilized protein-based methods are critically dependent on the strategies employed for protein immobilization. Compared with random immobilization approaches, site-specific covalent methods have emerged as promising alternatives, offering enhanced analytical performance. However, these methods typically require genetic modification of the target protein to incorporate a specific tag or prior purification of the protein, posing significant challenges for immobilizing endogenous proteins. Herein, we address these limitations by using the 5-hydroxytryptamine transporter (5-HTT) as a model system. We designed a probe by conjugating fluvoxamine─a specific ligand of 5-HTT─with either a fluorescent reporter or aminopropyl-modified silica gel through an alkyl linker containing an acyl imidazole moiety as the reactive group. By introducing ligand-directed acyl imidazole (LDAI) chemistry, we achieved selective labeling of 5-HTT in live cells and endogenous 5-HTT immobilization without purification in advance. Labeling experiments confirmed the high specificity and favorable kinetics of the LDAI ligands toward 5-HTT. Chromatographic analysis revealed significant improvements in selectivity (5.7-50.9-fold), resolution (1.2-3.0-fold), and sensitivity (1.0-12.0-fold) for analyzing canonical ligands when using immobilized endogenous 5-HTT, compared to His-tagged and Halo-tagged recombinant proteins. This approach, by substituting fluvoxamine with other ligands in the probe, can be generalized for the labeling and immobilization of a wide range of endogenous proteins, offering a versatile platform for advanced protein-based analytical techniques.

Brassinosteroid-induced S-nitrosylation of fructose-1,6-bisphosphate aldolase increased ATP synthesis under low temperatures in mini Chinese cabbage seedlings

Low temperature causes an imbalance in plant energy metabolism homeostasis. Brassinosteroids (BRs) are a class of hormones with important regulatory functions in plant responses to low temperature. S-nitrosylation of proteins is a key pathway for nitric oxide-mediated regulation of plant stress. In this study, we investigated whether S-nitrosylation proteins are involved in regulating energy metabolism in mini Chinese cabbage seedlings at low temperature. Low temperature inhibited the transcriptional accumulation of BrFBA2, BrGAPDH, BrPGK, and BrPK. However, applying exogenous BR and S-nitrosoglutathione significantly upregulated the transcription of these genes and accelerated the release of ATP. Exogenous BR significantly upregulated the S-nitrosylation level of fructose-1,6-bisphosphate aldolase 2 (FBA2) at low temperatures. FBA2 protein S-nitrosylation modification occurred in vitro at Cys-197. OE-BrFBA2 lines showed enhanced S-nitrosylation at low temperatures. Applying exogenous BR enhanced the S-nitrosylation of FBA2 and accelerated ATP release in TRV2-BrFBA2 lines. Exogenous BR treatment was conducive to maintaining the homeostasis of cell energy metabolism in mini Chinese cabbage seedlings at low temperature.

Biohybrid Nanosystem Fabricated with Marine Diatom Thalassiosira pseudonana for Uric Acid Detection

Due to the intense demand for low-cost, environmentally friendly, and stable uric acid (UA) detection methods, a novel biosensing nanosystem made with marine diatom was studied. Reduced by live diatom (Thalassiosira pseudonana), metallic nanoparticles (CuX) were hybridized with the heteronanostructure (Diatom frustule, DF), showing peroxidase activity 2.66-fold over horseradish peroxidase (HRP). To immobilize the enzyme directionally with increasing loading amounts, silaffin peptides (R5 and T8) were designed for tagging the urate oxidase (UoX). The enzyme loading on DF of tagged UoX was 1.76-fold (R5) and 1.54-fold (T8) that of untagged UoX. The activity of immobilized UoX-R5 was 5.29-11.76-fold more than that of free UoX-R5 at various pH levels (5-10) and temperatures (20-60 °C). The nanosystem (UoX-R5 immobilized on CuX-coated diatom frustules, termed as BioHNS) demonstrated a superior linear range of 5 × 10-6 to 1 × 10-3 M and a detection limit of 1.6 μM, surpassing the performance of the majority of reported UA sensors. The recoveries of UA in urine were detected by the BioHNS, ranging from 96.93 to 105.35%, with a relative deviation of less than 5.00%. The BioHNS showed excellent anti-interference and storage stability (2 months). In summary, BioHNS demonstrates significant potential as a sustainable and environmentally friendly biosensor for uric acid detection, highlighting its substantial relevance to the biomedical applications of marine diatoms.

A Comprehensive Guide to Enzyme Immobilization: All You Need to Know

Enzyme immobilization plays a critical role in enhancing the efficiency and sustainability of biocatalysis, addressing key challenges such as limited enzyme stability, short shelf life, and difficulties in recovery and recycling, which are pivotal for green chemistry and industrial applications. Classical approaches, including adsorption, entrapment, encapsulation, and covalent bonding, as well as advanced site-specific methods that integrate enzyme engineering and bio-orthogonal chemistry, were discussed. These techniques enable precise control over enzyme orientation and interaction with carriers, optimizing catalytic activity and reusability. Key findings highlight the impact of immobilization on improving enzyme performance under various operational conditions and its role in reducing process costs through enhanced stability and recyclability. The review presents numerous practical applications of immobilized enzymes, including their use in the pharmaceutical industry for drug synthesis, in the food sector for dairy processing, and in environmental biotechnology for wastewater treatment and dye degradation. Despite the significant advantages, challenges such as activity loss due to conformational changes and mass transfer limitations remain, necessitating tailored immobilization protocols for specific applications. The integration of immobilization with modern biotechnological advancements, such as site-directed mutagenesis and recombinant DNA technology, offers a promising pathway for developing robust, efficient, and sustainable biocatalytic systems. This comprehensive guide aims to support researchers and industries in selecting and optimizing immobilization techniques for diverse applications in pharmaceuticals, food processing, and fine chemicals.

Recombinant bovine serum albumin domain II as bioreceptor for ochratoxin A capture

Established chromatographic techniques for mycotoxin control in foodstuffs require prior sample enrichment and clean-up, typically achieved using immunoaffinity columns (IACs). Bovine serum albumin (BSA) has recently emerged as a cost-effective alternative to antibodies used in IACs. This study aimed at exploring the BSA domain II (BDII), which houses the primary binding site for ochratoxin A (OTA), as a bioreceptor for OTA capture. Recombinant BDII (rBDII) was produced in soluble form by Escherichia coli Origami 2(DE3), fused to a His6 (HisBDII) or thioredoxin-His6 (TrxBDII) tag, with yields up to 19 ± 4.3 mg/Lculture in shake-flask. Fluorescence and circular dichroism (CD) spectroscopy revealed interaction of OTA with both rBDII variants, with estimated binding constants for OTA-HisBDII/TrxBDII complexes in the range of 5.7-9.3 × 104 M-1. CD also showed an α/β structure of rBDII variants, in opposition to the predominant α-helical structure of whole BSA, and slight increase in their α-helical content upon binding to OTA. TrxBDII immobilized on Ni-NTA resin successfully captured OTA from spiked samples at the optimum pH range of 6.5-7.0, allowing OTA extraction, clean-up, and enrichment from spiked white grape juice, with up to 84 ± 7.4 % recovery.

A Strep-Tag Imprinted Polymer Platform for Heterogenous Bio(electro)catalysis

Molecularly imprinted polymers (MIPs) are artificial receptors equipped with selective recognition sites for target molecules. One of the most promising strategies for protein MIPs relies on the exploitation of short surface-exposed protein fragments, termed epitopes, as templates to imprint binding sites in a polymer scaffold for a desired protein. However, the lack of high-resolution structural data of flexible surface-exposed regions challenges the selection of suitable epitopes. Here, we addressed this drawback by developing a polyscopoletin-based MIP that recognizes recombinant proteins via imprinting of the widely used Strep-tag II affinity peptide (Strep-MIP). Electrochemistry, surface-sensitive IR spectroscopy, and molecular dynamics simulations were employed to ensure an utmost control of the Strep-MIP electrosynthesis. The functionality of this novel platform was verified with two Strep-tagged enzymes: an O2-tolerant [NiFe]-hydrogenase, and an alkaline phosphatase. The enzymes preserved their biocatalytic activities after multiple utilization confirming the efficiency of Strep-MIP as a general biocompatible platform to confine recombinant proteins for exploitation in biotechnology.

Engineered Protein Hydrogels as Biomimetic Cellular Scaffolds

The biochemical and biophysical properties of the extracellular matrix (ECM) play a pivotal role in regulating cellular behaviors such as proliferation, migration, and differentiation. Engineered protein-based hydrogels, with highly tunable multifunctional properties, have the potential to replicate key features of the native ECM. Formed by self-assembly or crosslinking, engineered protein-based hydrogels can induce a range of cell behaviors through bioactive and functional domains incorporated into the polymer backbone. Using recombinant techniques, the amino acid sequence of the protein backbone can be designed with precise control over the chain-length, folded structure, and cell-interaction sites. In this review, the modular design of engineered protein-based hydrogels from both a molecular- and network-level perspective are discussed, and summarize recent progress and case studies to highlight the diverse strategies used to construct biomimetic scaffolds. This review focuses on amino acid sequences that form structural blocks, bioactive blocks, and stimuli-responsive blocks designed into the protein backbone for highly precise and tunable control of scaffold properties. Both physical and chemical methods to stabilize dynamic protein networks with defined structure and bioactivity for cell culture applications are discussed. Finally, a discussion of future directions of engineered protein-based hydrogels as biomimetic cellular scaffolds is concluded.

Advancements in nanobody generation: Integrating conventional, in silico, and machine learning approaches

Nanobodies, derived from camelids and sharks, offer compact, single-variable heavy-chain antibodies with diverse biomedical potential. This review explores their generation methods, including display techniques on phages, yeast, or bacteria, and computational methodologies. Integrating experimental and computational approaches enhances understanding of nanobody structure and function. Future trends involve leveraging next-generation sequencing, machine learning, and artificial intelligence for efficient candidate selection and predictive modeling. The convergence of traditional and computational methods promises revolutionary advancements in precision biomedical applications such as targeted drug delivery and diagnostics. Embracing these technologies accelerates nanobody development, driving transformative breakthroughs in biomedicine and paving the way for precision medicine and biomedical innovation.

Development of a label-free electrochemical aptasensor for Rift Valley fever virus detection

In this research, we describe the first aptasensor for the detection of the Rift Valley Fever virus (RVFV). The process involved the selection of aptamers through the systematic evolution of ligands by the exponential enrichment (SELEX) technique. After 12 rounds of selection, 6 aptamers were selected and the corresponding binding affinities were assessed using fluorescence binding assays, revealing dissociation constants ranging from 15.45 to 40.98 nM. Notably, among the aptamers, RV2 and RV3 exhibited the highest binding affinities toward RVFV, with dissociation constants of 15.45 and 18.62 nM, respectively. Thiol-modified aptamers were subsequently immobilized onto screen-printed gold electrodes, facilitating the label-free detection of RVFV through square wave voltammetry. The voltammetric aptasensor demonstrated an excellent sensitivity, with a detection limit of 0.015 ng/mL. In addition, cross-reactivity assessments were conducted, where negligible response was obtained when the aptasensor was exposed to non-specific proteins.

A carbon-based bifunctional heterogeneous enzyme: toward sustainable pollution control

We present a study on an immobilized functional enzyme (IFE), a novel biomaterial with exceptional sustainability in enzyme utility, widely employed across various fields worldwide. However, conventional carriers are prone to eroding the active functional domain of the IFE, thereby weakening its intrinsic enzyme activity. Consequently, there is a burgeoning interest in developing next-generation IFEs. In this study, we engineered a carbon-based bifunctional heterogeneous enzyme (MIP-AMWCNTs@lipase) for the intelligent recognition of di(2-ethylhexyl)phthalate (DEHP), a common plasticizer. The heterogeneous enzyme contains a bifunctional structural domain that both enriches and degrades DEHP. We investigated its dual-response performance for the enrichment and specific removal of DEHP. The imprinting factor of the carrier for DEHP was 3.4, demonstrating selectivity for DEHP. The removal rate reached up to 94.2% over a short period. The heterogeneous enzyme exhibited robust activity, catalytic efficiency, and excellent stability under harsh environmental conditions, retaining 77.7% of its initial lipase activity after 7 cycles. Furthermore, we proposed a stepwise heterogeneous enzyme reaction kinetic model based on the Michaelis-Menten equation to enhance our understanding of enzyme reaction kinetics. Our study employs a dual-effect recognition strategy of molecular blotting and enzyme immobilization to establish a method for the removal of organic pollutants. These findings hold significant implications for the fields of biomaterials and environmental science.

Efficient and easible biocatalysts: Strategies for enzyme improvement. A review

Owing to the environmental friendliness and vast advantages that enzymes offer in the biotechnology and industry fields, biocatalysts are a prolific investigation field. However, the low catalytic activity, stability, and specific selectivity of the enzyme limit the range of the reaction enzymes involved in. A comprehensive understanding of the protein structure and dynamics in terms of molecular details enables us to tackle these limitations effectively and enhance the catalytic activity by enzyme engineering or modifying the supports and solvents. Along with different strategies including computational, enzyme engineering based on DNA recombination, enzyme immobilization, additives, chemical modification, and physicochemical modification approaches can be promising for the wide spread of industrial enzyme usage. This is attributed to the successful application of biocatalysts in industrial and synthetic processes requires a system that exhibits stability, activity, and reusability in a continuous flow process, thereby reducing the production cost. The main goal of this review is to display relevant approaches for improving enzyme characteristics to overcome their industrial application.

A universal method for surface-based binding assays by preparing immobilized β2-adrenergic receptor stationary phase using solid binding peptide as a fusion tag

Protein functionalized surface has the potential to develop new assays for determining the drug-like properties of potential compounds and discovering specific partners of G protein-coupled receptors (GPCRs). However, a universal method for purifying and immobilizing functional GPCRs has remained elusive. To this end, we developed a general and rapid way to purify and immobilize β2-adrenergic receptor (β2AR) by silicon-specific peptide. We screened CotB1p as a tag from six silica-binding peptides (minTBP-1, CotB1p, SB7, Car9, and Si4-1) by examining their affinity to macroporous silica gel. We investigated the adsorption and desorption of CotB1p-tagged β2-adrenoceptor (β2AR-CotB1p) under diverse conditions to propose a protocol for receptor purification and immobilization. Under optimized conditions, β2AR immobilization were achieved by directly immersing cell lysates harboring the receptor with silica gel, and the elution of the receptor without demonstratable contaminants was realized by including l-arginine/L-lysine in the elutes. This allows purification of the receptor from Escherichia coli (E.coli) lysates with a purity of 95 %. The immobilized receptor was utilized as a stationary phase to reveal the tag impact on ligand-binding outputs by comparing the CotB1p-strategy with a typical covalent method. The KAs of salbutamol, chlorprenaline, tulobuterol, and terbutaline on β2AR-CotB1p column were 1.26 × 106, 6.59 × 106, 7.90 × 106, and 8.97 × 105 M-1 respectively, which were two orders of magnitude higher than those on the Halo-β2AR column. The whole immobilization was accomplished within 30 min without the requirement of any special treatment, resulting in enhanced accuracy for determining receptor-ligand binding parameters. Taken together, CotB1p-mediated strategy is simple, rapid, and universal for purification or immobilization of unstable biomolecules like GPCRs for analytical and biological applications.

Oriented immobilization of nanobodies using SpyCatcher/SpyTag significantly enhances the capacity of affinity chromatography

The use of nanobodies (Nbs) in affinity chromatography for biomacromolecule purification is gaining popularity. However, high-performance Nb-based affinity resins are not readily available, mainly due to the lack of suitable immobilization methods. In this study, we explored an autocatalytic coupling strategy based on the SpyCatcher/SpyTag chemistry to achieve oriented immobilization of Nb ligands. To facilitate this approach, a variant cSpyCatcher003 (cSC003) was coupled onto agarose microspheres, providing a specific attachment site for SpyTagged nanobody ligands. The cSC003 easily purified from Escherichia coli through a two-step procedure, exhibits exceptional alkali resistance and structural recovery capability, highlighting its robustness as a linker in the coupling strategy. To validate the effectiveness of cSC003-derivatized support, we employed VHSA, a nanobody against human serum albumin (HSA), as the model ligand. Notably, the immobilization of SpyTagged VHSA onto the cSC003-derivatized support was achieved with a coupling efficiency of 90 %, significantly higher than that of traditional thiol-based coupling method. This improvement directly correlated to the preservation of the native conformation of nanobodies during the coupling process. In addition, the Spy-immobilized resin demonstrated better performance in the binding capacity, with a 3-fold improvement in capture efficiency, underscoring the advantages of the Spy immobilization strategy for oriented immobilization of VHSA ligands. Moreover, online purification and immobilization of SpyTagged VHSA from crude bacterial lysate was achieved using the cSC003-derivatized support. The resulting resin exhibited high binding specificity towards HSA, yielding a purity above 95 % directly from human serum, and maintained good stability throughout multiple purification cycles. These findings highlight the potential of the Spy immobilization strategy for developing Nb-based affinity chromatographic materials, with significant implications for biopharmaceutical downstream processes.

Microbial Immobilized Enzyme Biocatalysts for Multipollutant Mitigation: Harnessing Nature's Toolkit for Environmental Sustainability

The ever-increasing presence of micropollutants necessitates the development of environmentally friendly bioremediation strategies. Inspired by the remarkable versatility and potent catalytic activities of microbial enzymes, researchers are exploring their application as biocatalysts for innovative environmental cleanup solutions. Microbial enzymes offer remarkable substrate specificity, biodegradability, and the capacity to degrade a wide array of pollutants, positioning them as powerful tools for bioremediation. However, practical applications are often hindered by limitations in enzyme stability and reusability. Enzyme immobilization techniques have emerged as transformative strategies, enhancing enzyme stability and reusability by anchoring them onto inert or activated supports. These improvements lead to more efficient pollutant degradation and cost-effective bioremediation processes. This review delves into the diverse immobilization methods, showcasing their success in degrading various environmental pollutants, including pharmaceuticals, dyes, pesticides, microplastics, and industrial chemicals. By highlighting the transformative potential of microbial immobilized enzyme biocatalysts, this review underscores their significance in achieving a cleaner and more sustainable future through the mitigation of micropollutant contamination. Additionally, future research directions in areas such as enzyme engineering and machine learning hold immense promise for further broadening the capabilities and optimizing the applications of immobilized enzymes in environmental cleanup.

Intein Based Fusion Proteins: Great Tags for the Soluble Production and Convenient Purification of Recombinant Proteins

Background

The main problem in the recombinant protein expression in E. coli strains, especially for high-yield production, is the accumulation in un-folded and inactive inclusion bodies. A suitable solution is the direction into the soluble cytoplasmic products by solubilizing tags. The use of inteins with self-cleaving ability, in addition to increase the chance of soluble protein expression, facilitates their purification process.

Evidence Acquisition

In this review article, papers related to the use of intein tags for soluble expression or protein purification were collected regardless the time limit. Available databases including Pubmed, google scholar, ScienceDirect, Web of Science, Scopus, and Embase was searched. The best condition for soluble expression or purification was focused in all articles.

Results

There are various intein tags commercially available in expression vectors that results in gaining our goal in facilitating the recombinant protein solubilization as well as its simple purification. It is enough to induce the self-cleavage property of the intein, which varies according to the type of intein used. In this way, the target protein is easily separated from the purification tag without the need to add protease enzymes such as enterokinase or treatment with various chemicals. The most common affinity tag in intein-based systems is Chitin Binding Domain attached to the chitin resin.

Conclusions

In this review article, we introduced proteins or peptides which produced in fusion to intein tags and discussed about their expression condition and purification process in order to enhance the chance of soluble expression and intein cleavage in a single stage, respectively.

Extremozyme-Based Biosensors for Environmental Pollution Monitoring: Recent Developments

Extremozymes combine high specificity and sensitivity with the ability to withstand extreme operational conditions. This work presents an overview of extremozymes that show potential for environmental monitoring devices and outlines the latest advances in biosensors utilizing these unique molecules. The characteristics of various extremozymes described so far are presented, underlining their stability and operational conditions that make them attractive for biosensing. The biosensor design is discussed based on the detection of photosynthesis-inhibiting herbicides as a case study. Several biosensors for the detection of pesticides, heavy metals, and phenols are presented in more detail to highlight interesting substrate specificity, applications or immobilization methods. Compared to mesophilic enzymes, the integration of extremozymes in biosensors faces additional challenges related to lower availability and high production costs. The use of extremozymes in biosensing does not parallel their success in industrial applications. In recent years, the "collection" of recognition elements was enriched by extremozymes with interesting selectivity and by thermostable chimeras. The perspectives for biosensor development are exciting, considering also the progress in genetic editing for the oriented immobilization of enzymes, efficient folding, and better electron transport. Stability, production costs and immobilization at sensing interfaces must be improved to encourage wider applications of extremozymes in biosensors.

The impact of chemical properties of the solid-liquid-adsorbate interfaces on the entropy-enthalpy compensation involved in adsorption

Despite extensive studies on the thermodynamic mechanism governing molecular adsorption at the solid-water interface, a comprehensive understanding of the crucial role of interface properties in mediating the entropy-enthalpy compensation during adsorption is lacking, particularly at a quantitative level. Herein, we employed two types of surface models (hydroxyapatite and graphene) along with a series of amino acids to successfully elucidate how distinct interfacial features dictate the delicate balance between entropy and enthalpy variations. The adsorption of all amino acids on the hydroxyapatite surface is an enthalpy-dominated process, where the water-induced enthalpic component of the free energy and the surface-adsorbate electrostatic interaction term alternatively act as the driving force for adsorption in different regions of the surface. Although favorable interactions are observed between amino acids and the graphene surface, the entropy-enthalpy compensation exhibits dependence on the molecular size of the adsorbates. For small amino acids, favorable enthalpy changes predominantly determine their adsorption behavior; however, larger amino acids tend to bind more tightly with the graphene surface, which is thermodynamically dominated by the entropy variations despite the structural characteristics of amino acids. This study reveals specific entropy-enthalpy mechanisms underlying amino acid adsorption at the solid-liquid interface, providing guidance for surface design and synthesis of new biomolecules.

Preparation of a novel metallothionein-AuNP composite material by genetic modification and AuS covalent combination

Metallothionein (MTs) can be used in the prevention and treatment of tumors and diabetes due to its antioxidant properties. However, it is necessary to solve its non-transmembrane properties and further improve its antioxidant activity, increase its fluorescence visualization and enhance its stability to meet practical applications in the biomedical field. Here, we report the preparation of a novel metallothionein-AuNP composite material with high transmembrane ability, fluorescence visualization, antioxidant activity, and stability by genetic modification (introducing transduction peptide TAT, fluorescence tag GFP and increasing sulfydryl groups) and immobilization technology (covalently bonding with AuNPs). The transmembrane activity of modified proteins was verified by immunofluorescence. Increasing the sulfhydryl content within a certain range can enhance the antioxidant activity of the protein. In addition, GFP were used to further simplify the imaging of the metallothionein-AuNP composite in cells. XPS results indicated that AuNPs can immobilize metallothionein through AuS covalent bonds. TGA characterization and degradation experiments showed that thermal and degradation stability of the immobilized material was significantly improved. This work provides new ideas to construct metallothionein composites with high transmembrane ability, antioxidant activity, fluorescence visualization and stability to meet novel applications in the biomedical field.

Efficient Biosynthesis of Difucosyllactose via De Novo GDP-l-Fucose Pathway in Metabolically Engineered Escherichia coli

Difucosyllactose (DFL) is an important component of human milk oligosaccharides (HMOs) and has significant benefits for the growth and development of infants. So far, a few microbial cell factories have been constructed for the production of DFL, which still have problems of low production and high cost. Herein, a high-level de novo pathway DFL-producing strain was constructed by multistep optimization strategies in Escherichia coli BL21star(DE3). We first efficiently synthesized the intermediate 2'-fucosyllactose (2'-FL) in E. coli BL21star(DE3) by the advisable stepwise strategy. The truncated α-1,3/4-fucosyltransferase (Hp3/4FT) was then introduced into the engineered strain to achieve de novo biosynthesis of DFL. ATP-dependent protease (Lon) and GDP-mannose hydrolase (NudK) were deleted, and mannose-6-phosphate isomerase (ManA) was overexpressed to improve GDP-l-fucose accumulation. The regulator RcsA was overexpressed to fine-tune the expression level of pathway genes, thereby increasing the synthesis of DFL. The final strain produced 6.19 g/L of DFL in the shake flask and 33.45 g/L of DFL in the 5 L fermenter, which were the highest reported titers so far. This study provides a more economical, sustainable, and effective strategy to produce the fucosylated human milk oligosaccharides (HMOs).

On-column refolding and off-column assembly of parvovirus B19 virus-like particles from bacteria-expressed protein

Virus-like particles (VLPs) are nanometric structures composed of structural components of virions, keeping most of the cellular recognition and internalization properties, but are non-infective as they are deprived of their genetic material. VLPs have been a versatile platform for developing vaccines by carrying their own or heterologous antigenic epitopes. Moreover, VLPs can also be used as nanovessels for encapsulating molecules with therapeutic applications, like enzymes, nucleic acids, and drugs. Parvovirus B19 (B19V) VLPs can be self-assembled in vitro from the denatured major viral particle protein VP2 by equilibrium dialysis. Despite its fair productivity, this process is currently a time-consuming task. Affinity chromatography is used as an efficient step for concentration and purification, but it is only sometimes seen as a method that facilitates the oligomerization of proteins. In this research, we report a novel approach for the in vitro assembly of B19V VLPs through the immobilization of the denatured VP2 into an immobilized metal affinity chromatography (IMAC) column, followed by the on-column folding and the final VLP assembly upon protein elution. This method is suitable for the fast production of B19V VLPs. KEY POINTS: • Biotechnological applications for inclusion bodies • Efficient single-step purification and immobilization strategies • Rapid VLP assembly strategy.

Recombinant protein purification and immobilization strategies based on peptides with dual affinity to iron oxide and silica

Iron oxide and silica-based materials have emerged as attractive protein purification and immobilization matrices. His6 has been reported as an effective affinity tag for both iron oxide and silica. Here, the silica-binding tags CotB1p and Car9 were shown to work as effectively as iron oxide-binding tags. Using EGFP as a model protein, commercially available bare iron oxide (BIONs) or silicon dioxide (BSiNs) nanoparticles as low-cost purification/immobilization matrices, and non-hazardous and mild binding and elution conditions, adsorption and desorption studies were performed with lysates from Escherichia coli-producing cells to compare the performance of these dual-affinity tags. Under the conditions tested, the His6 tag stood out as the best-performing tag, followed by CotB1p. Our findings concluded the promising combination of these tags, BIONs and BSiNs for one-step purification of recombinant proteins, and two-step purification and immobilization of recombinant proteins without intermediate buffer exchange. This proof of concept work set the ground for future evaluation of these purification and immobilization strategies using other proteins with different properties, which will be of interest to expand their utility and applicability.

Research progress of multi-enzyme complexes based on the design of scaffold protein

Multi-enzyme complexes designed based on scaffold proteins are a current topic in molecular enzyme engineering. They have been gradually applied to increase the production of enzyme cascades, thereby achieving effective biosynthetic pathways. This paper reviews the recent progress in the design strategy and application of multi-enzyme complexes. First, the metabolic channels in the multi-enzyme complex have been introduced, and the construction strategies of the multi-enzyme complex emerging in recent years have been summarized. Then, the discovered enzyme cascades related to scaffold proteins are discussed, emphasizing on the influence of the linker on the fusion enzyme (fusion protein) and its possible mechanism. This review is expected to provide a more theoretical basis for the modification of multi-enzyme complexes and broaden their applications in synthetic biology.

Synthesis of micron-sized magnetic agarose beads chelated with nickel ions towards the affinity-based separation of histidine-tagged/rich proteins

Developing high-performance magnetic particles for the effective separation and purification of target proteins has become an important topic in the area of biomedical research. In this work, a simple and novel strategy was proposed for fabricating magnetic Fe3O4@agarose-iminodiacetic acid-Ni microspheres (MAIN), which can efficiently and selectively isolate histidine-tagged/rich proteins (His-proteins). Based on the thermoreversible sol-gel transition of agarose, basic magnetic agarose microspheres were prepared through the inverse emulsion method, in which the emulsion contained agarose and amine-modified Fe3O4 nanoparticles. The size of the emulsion was controlled by the emulsification of a high-speed shear machine, which improved the specific surface area of MAIN. Subsequently, the amine-modified Fe3O4 nanoparticles were covalently crosslinked with agarose through epichlorohydrin, which could avoid leakage of the magnetic source during use and increase the stability of MAIN. The microsized MAIN exhibited a clearly visible spherical core-shell structure with a diameter range from 3.4 μm to 9.8 μm, and excellent suspension ability in aqueous solution. The maximum adsorption capacity of MAIN for histidine-rich bovine hemoglobin was 1069.2 mg g-1 at 35 °C, which was higher than those of commercialized and most reported magnetic agarose microspheres/nanoparticles. The MAIN showed excellent adsorption ability and selectivity toward His-proteins in a mixture of histidine-rich bovine serum albumin (BSA) and histidine-poor lysozyme (LYZ). When the amount of LYZ was 5-fold higher than that of BSA, the recovery of BSA reached 75.0%. To prove its practicability, MAIN was successfully employed for the enrichment of histidine-tagged RSV-F0 from the cell culture medium supernatant. According to the optimized conditions, MAIN could enrich approximately 0.1 mg of RSV-F0 from 1 mL of complex biological sample. Therefore, we believe that the novel MAIN could be applicable for efficient separation and purification of His-proteins from complex biological systems.

N-terminal LysSN-His-tag improves the production of intracellular recombinant protein in Bacillus subtilis

Choosing fusion tags to enhance the recombinant protein levels in the cytoplasm of Bacillus subtilis has been limited. Our previous study demonstrated that His-tag at the N-terminus could increase the expression levels of the low-expression gene egfp, while significantly reducing the high-expression genes gfp+ and bgaB in the cytoplasm of B. subtilis. In this study, we aimed to prove the potential of a fusion tag, the combination of the N-terminal domain of B. subtilis lysyl tRNA synthetase (LysSN) and His-tag with varying numbers of histidine (6xHis, 8xHis, 10xHis) by investigating their effects on the expression levels of egfp, gfp+ and bgaB in B. subtilis. For the low-expression gene, LysSN-xHis-tag could enhance the fluorescent intensity of EGFP 23.5 times higher than EGFP without a fusion tag, and 1.5 times higher than that fused with only His-tag. For high-expression genes, the expression level of BgaB and GFP+ was 2.9 and 12.5 times higher than that of His-tag, respectively. The number of histidines in LysSN-xHis-tag did not influence the expression levels of the high-expression genes but affected the expression levels of the low-expression gene.

Non-covalent binding tags for batch and flow biocatalysis

Enzyme immobilization offers considerable advantage for biocatalysis in batch and continuous flow reactions. However, many currently available immobilization methods require that the surface of the carrier is chemically modified to allow site specific interactions with their cognate enzymes, which requires specific processing steps and incurs associated costs. Two carriers (cellulose and silica) were investigated here, initially using fluorescent proteins as models to study binding, followed by assessment of industrially relevant enzyme performance (transaminases and an imine reductase/glucose oxidoreductase fusion). Two previously described binding tags, the 17 amino acid long silica-binding peptide from the Bacillus cereus CotB protein and the cellulose binding domain from the Clostridium thermocellum, were fused to a range of proteins without impairing their heterologous expression. When fused to a fluorescent protein both tags conferred high avidity specific binding with their respective carriers (low nanomolar K_d values). The CotB peptide (CotB1p) induced protein aggregation in the transaminase and imine reductase/glucose oxidoreductase fusions when incubated with the silica carrier. The Clostridium thermocellum cellulose binding domain (CBDclos) allowed immobilization of all the proteins tested, but immobilization led to loss of enzymatic activity in the transaminases (< 2-fold) and imine reductase/glucose oxidoreductase fusion (> 80%). A transaminase-CBDclos fusion was then successfully used to demonstrate the application of the binding tag in repetitive batch and a continuous-flow reactor.

A systematic review about affinity tags for one-step purification and immobilization of recombinant proteins: integrated bioprocesses aiming both economic and environmental sustainability

The present study reviewed and discussed the promising affinity tags for one-step purification and immobilization of recombinant proteins. The approach used to structure this systematic review was The Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) methodology. The Scopus and Web of Science databases were used to perform the bibliographic survey by which 267 articles were selected. After the inclusion/exclusion criteria and the screening process, from 25 chosen documents, we identified 7 types of tags used in the last 10 years, carbohydrate-binding module tag (CBM), polyhistidine (His-tag), elastin-like polypeptides (ELPs), silaffin-3-derived pentalysine cluster (Sil3k tag), N-acetylmuramidase (AcmA tag), modified haloalkane dehalogenase (HaloTag®), and aldehyde from a lipase polypeptide (Aldehyde tag). The most used bacterial host for expressing the targeted protein was Escherichia coli and the most used expression vector was pET-28a. The results demonstrated two main immobilization and purification methods: the use of supports and the use of self-aggregating tags without the need of support, depending on the tag used. Besides, the chosen terminal for cloning the tag proved to be very important once it could alter enzyme activity. In conclusion, the best tag for protein one-step purification and immobilization was CBM tag, due to the eco-friendly supports that can be provided from industry wastes, the fast immobilization with high specificity, and the reduced cost of the process.

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.

Covalent binding modes between BMP-2-derived peptides and graphene in 3D scaffolds determine their osteoinductivity and capacity for calvarial defect repair in vivo

Covalent introduction of bioactive molecules is one of main strategies to significantly enhance the biological activities of bone repair materials. In this study, three most-commonly used chemical groups were respectively introduced on graphene (GP), followed by covalent binding with bone morphogenetic protein-2 (BMP-2) -derived peptides, ensuring that the same molar mass of peptides was bound to different functionalized GP (f-GP). Then the same amount of composites composed of different f-GP and peptides were respectively compounded with poly (lactic-co-glycolic acid) to fabricate 3D scaffolds. In vivo study demonstrated that the scaffolds containing ammonized GP covalently bound with the peptides through amide binding could reach best efficiency of promoting ectopic bone regeneration and repairing calvarial defect probably because the most positive charges on the peptide chain and surface of the ammonized GP could absorb more specific proteins in vivo and have better interactions with them, thereby differentiating most inducible cells into osteogenic cells. Our results indicate that the performances of scaffolds containing covalently bound bioactive molecules can be controlled by the covalent binding mode, and that our prepared scaffold containing ammonized GP covalently bound with the BMP-2-derived peptides through amide binding possess inspiring potential applicable prospects for bone tissue regeneration and engineering.

Recycling of hyoscyamine 6β-hydroxylase for the in vitro production of anisodamine and scopolamine

The tropane alkaloids hyoscyamine, anisodamine, and scopolamine are extensively used medicines. In particular, scopolamine has the greatest value in the market. Hence, strategies to enhance its production have been explored as an alternative to traditional field-plant cultivation. In this work, we developed biocatalytic strategies for the transformation of hyoscyamine into its products utilizing a recombinant Hyoscyamine 6β-hydroxylase (H6H) fusion protein to the chitin-binding domain of the chitinase A1 from Bacillus subtilis (ChBD-H6H). Catalysis was carried out in batch, and recycling of H6H constructions was performed via affinity-immobilization, glutaraldehyde crosslinking, and adsorption-desorption of the enzyme to different chitin matrices. ChBD-H6H utilized as free enzyme achieved complete conversion of hyoscyamine in 3- and 22-h bioprocesses. Chitin particles demonstrated to be the most convenient support for ChBD-H6H immobilization and recycling. Affinity-immobilized ChBD-H6H operated in a three-cycle bioprocess (3 h/cycle, 30 °C) yielded in the first and third reaction cycle 49.8% and 22.2% of anisodamine and 0.7% and 0.3% of scopolamine, respectively. However, glutaraldehyde crosslinking decreased enzymatic activity in a broad range of concentrations. Instead, the adsorption-desorption approach equaled the maximal conversion of the free enzyme in the first cycle and retained higher enzymatic activity than the carrier-bound strategy along the consecutive cycles. The adsorption-desorption strategy permitted the reutilization of the enzyme in a simple and economical manner while exploiting the maximal conversion activity displayed by the free enzyme. This approach is valid since other enzymes present in the E. coli lysate do not interfere with the reaction. KEY POINTS: • A biocatalytic system for anisodamine and scopolamine production was developed. • Affinity-immobilized ChBD-H6H in ChP retained catalytic activity. • Enzyme-recycling by adsorption-desorption strategies improves product yields.

Biomimetic one-pot preparation of surface biofunctionalized silica-coated magnetic composites for dual enzyme oriented immobilization without pre-purification

Surface functioned magnetic silica particles are efficient carriers to achieve facilitated separation and recycling of biocatalysts. However, traditional methods of modifying magnetic silica particles required time-costly sequential coating and surface modification steps and toxic solvents. Herein, a green and efficient routine was proposed to prepare the surface modified silica-coated magnetic microspheres (SCEs@SiO₂ @Fe₃O₄) in one-pot. The elastin-like polypeptides (ELPs)-SpyCatcher chimera (SCEs) were purified by inverse transition cycling with high yield (275 mg/L) and incorporated into the magnetic silica spheres based on the biomimetic silicification capability of ELPs as proved by the EDS and SEM mapping. No SCEs leaked was observed within 48 h, indicating excellent stability in buffer. Then, the biofunctionalized carriers were used to purify and immobilize the target dual enzymes (xylanase-linker-SpyTag-linker-lichenase, bienzymes) directly from the crude cell lysis solution by the spontaneous isopeptide bond reaction between SpyCatcher and SpyTag. The immobilized bienzymes were sphere-like magnetic silica particles with uniform size, which had good magnetic responsiveness. The immobilization yield, immobilization efficiency and activity recovery for xylanase were 86%, 84 % and 72 %, while for lichenase was 92 %, 86 % and 79 %, respectively. Besides, the immobilized bienzymes showed good reusability (>60 %, 10 times for xylanase, >95 %, 8 times for lichenase). The SCEs modified silica-coated magnetic microspheres are expected to provide versatile platforms for single-step of purification and immobilization of multienzymes, offering great potentials in the field of biocatalysis.

Novel Approach for the Isolation and Immobilization of a Recombinant Transaminase: Applying an Advanced Nanocomposite System

The increasing application of recombinant enzymes demands not only effective and sustainable fermentation, but also highly efficient downstream processing and further stabilization of the enzymes by immobilization. In this study, a novel approach for the isolation and immobilization of His-tagged transaminase from Chromobacterium violaceum (CvTA) has been developed. A recombinant of CvTA was simultaneously isolated and immobilized by binding on silica nanoparticles (SNPs) with metal affinity linkers and additionally within poly(lactic acid) (PLA) nanofibers. The linker length and the nature of the metal ion significantly affected the enzyme binding efficiency and biocatalytic activity of CvTA-SNPs. The formation of PLA nanofibers by electrospinning enabled rapid embedding of CvTA-SNPs biocatalysts and ensured enhanced stability and activity. The developed advanced immobilization method reduces the time required for enzyme isolation, purification and immobilization by more than fourfold compared to a classical stepwise technique.

Megaprimer-Based PCR to Synthesize Fusion Genes for Cloning

Megaprimer-based polymerase chain reaction (PCR) strategies allow the versatile and fast assembly and amplification of a myriad of tailor-made or random DNA sequences readily available for conventional or restriction-free (RF) cloning.In this chapter, we present a megaprimer-based PCR protocol that enables the expeditious construction of customized fusion genes ready for cloning into commercial expression plasmids. With the expanding use of protein tag technology in the most diverse application fields, this protocol remains a versatile and affordable solution for the synthesis and fusion of peptide tags/domains of interest.

Poly-Histidine-Tagged Protein Purification Using Immobilized Metal Affinity Chromatography (IMAC)

His-tagging is the most widespread and versatile strategy used to purify recombinant proteins for biochemical and structural studies. Recombinant DNA methods are first used to engineer the addition of a short tract of poly-histidine tag (His-tag) to the N-terminus or C-terminus of a target protein. The His-tag is then exploited to enable purification of the "tagged" protein by immobilized metal affinity chromatography (IMAC). In this chapter, we describe efficient procedures for the isolation of highly purified His-tagged target proteins from an Escherichia coli host using IMAC in a bind-wash-elute strategy that can be performed under both native and denaturing conditions.

1Progress, applications, challenges and prospects of protein purification technology

Protein is one of the most important biological macromolecules in life, which plays a vital role in cell growth, development, movement, heredity, reproduction and other life activities. High quality isolation and purification is an essential step in the study of the structure and function of target proteins. Therefore, the development of protein purification technologies has great theoretical and practical significance in exploring the laws of life activities and guiding production practice. Up to now, there is no forthcoming method to extract any proteins from a complex system, and the field of protein purification still faces significant opportunities and challenges. Conventional protein purification generally includes three steps: pretreatment, rough fractionation, and fine fractionation. Each of the steps will significantly affect the purity, yield and the activity of target proteins. The present review focuses on the principle and process of protein purification, recent advances, and the applications of these technologies in the life and health industry as well as their far-reaching impact, so as to promote the research of protein structure and function, drug development and precision medicine, and bring new insights to researchers in related fields.

Preparation of nickel-chelated iminodiacetate-functionalized macroporous agarose monolith using modular and clickable building blocks for affinity separation of histidine-tagged recombinant proteins

Selective separation and purification of protein from complex medium is required to completely investigate the structure and function of the target protein. In this study, a composite macroporous agarose monolith containing iminodiacetate-chelated Ni²⁺ ligands was synthesized for selective separation and purification of histidine-tagged recombinant proteins. The large and interconnected pores in the monolith enabled fast binding of proteins with high matrix tolerance in treating complex mediums. To realize the selective protein binding, the iminodiacetate was directly conjugated to epoxy-functionalized agarose monolith via simple chemical reactions between epoxy and imino groups. After chelated Ni²⁺, the composite monolith could bind histidine-tagged recombinant proteins through the coordination interaction between transition metal ions and the imidazole ring of histidine. To further increase the binding capacities of the monolith, a hydrophilic intermediate polymer chain containing multiple iminodiacetate immobilization sites was conjugated to the azide-functionalized agarose monolith via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The morphology and chemical composition of the composite agarose monolith were characterized systematically. The protein binding capacities of the obtained composite agarose monolith were subsequently investigated. The binding capacities of the composite agarose monolith towards the model proteins Gp10 and Lys84 were 0.93 and 0.51 mg/mL, respectively. The protein binding of the composite agarose monolith could be manipulated by adjusting the temperature and concentrations of imidazole. These results demonstrate that the composite agarose monolith could be used as an affinity medium for rapid separation and purification of histidine-tagged recombinant proteins from biological samples.

Putting precision and elegance in enzyme immobilisation with bio-orthogonal chemistry

The covalent immobilisation of enzymes generally involves the use of highly reactive crosslinkers, such as glutaraldehyde, to couple enzyme molecules to each other or to carriers through, for example, the free amino groups of lysine residues, on the enzyme surface. Unfortunately, such methods suffer from a lack of precision. Random formation of covalent linkages with reactive functional groups in the enzyme leads to disruption of the three dimensional structure and accompanying activity losses. This review focuses on recent advances in the use of bio-orthogonal chemistry in conjunction with rec-DNA to affect highly precise immobilisation of enzymes. In this way, cost-effective combination of production, purification and immobilisation of an enzyme is achieved, in a single unit operation with a high degree of precision. Various bio-orthogonal techniques for putting this precision and elegance into enzyme immobilisation are elaborated. These include, for example, fusing (grafting) peptide or protein tags to the target enzyme that enable its immobilisation in cell lysate or incorporating non-standard amino acids that enable the application of bio-orthogonal chemistry.

Programmable Polyproteams of Tyrosine Ammonia Lyases as Cross-Linked Enzymes for Synthesizing p-Coumaric Acid

Ideal immobilization with enhanced biocatalyst activity and thermostability enables natural enzymes to serve as a powerful tool to yield synthetically useful chemicals in industry. Such an enzymatic method strategy becomes easier and more convenient with the use of genetic and protein engineering. Here, we developed a covalent programmable polyproteam of tyrosine ammonia lyases (TAL-CLEs) by fusing SpyTag and SpyCatcher peptides into the N-terminal and C-terminal of the TAL, respectively. The resulting circular enzymes were clear after the spontaneous isopeptide bonds formed between the SpyTag and SpyCatcher. Furthermore, the catalytic performance of the TAL-CLEs was measured via a synthesis sample of p-Coumaric acid. Our TAL-CLEs showed excellent catalytic efficiency, with 98.31 ± 1.14% yield of the target product—which is 4.15 ± 0.08 times higher than that of traditional glutaraldehyde-mediated enzyme aggregates. They also showed over four times as much enzyme-activity as wild-type TAL does and demonstrated good reusability, and so may become a good candidate for industrial enzymes.

A Rationally Designed Building Block of the Putative Magnetoreceptor MagR

The ability of animals to perceive guidance cues from Earth's magnetic field for orientation and navigation has been supported by a wealth of behavioral experiments, yet the nature of this sensory modality remains fascinatingly unresolved and wide open for discovery. MagR has been proposed as a putative magnetoreceptor based on its intrinsic magnetism and its complexation with a previously suggested key protein in magnetosensing, cryptochrome, to form a rod-like polymer structure. Here, we report a rationally designed single-chain tetramer of MagR (SctMagR), serving as the building block of the hierarchical assembly of MagR polymer. The magnetic trapping experiment and direct magnetic measurement of SctMagR demonstrated the possibility of magnetization of nonmagnetic cells via overexpressing a single protein, which has great potential in various applications. SctMagR, as reported in this study, serves as a prototype of designed magnetic biomaterials inspired by animal magnetoreception. The features of SctMagR provide insights into the unresolved origin of the intrinsic magnetic moment, which is of considerable interest in both biology and physics. © 2022 Bioelectromagnetics Society.

Recent progress in the applications of silica-based nanoparticles

Functionalized silica nanoparticles (SiO2 NPs) have attracted great attention due to their promising distinctive, versatile, and privileged physiochemical characteristics. These enhanced properties make this type of functionalized nanoparticles particularly appropriate for different applications. A lack of reviews that summarizes the fabrications of such nanomaterials and their different applications in the same work has been observed in the literature. Therefore, in this work, we will discuss the recent signs of progress in the fabrication of functionalized silica nanoparticles and their attractive applications that have been extensively highlighted (advanced catalysis, drug-delivery, biomedical applications, environmental remediation applications, and wastewater treatment). These applications have been selected for demonstrating the role of the surface modification step on the various properties of the silica surface. In addition, the current challenges in the applications of functionalized silica nanoparticles and corresponding strategies to discuss these issues and future perspectives for additional improvement have been addressed.

Modulation of MagR magnetic properties via iron-sulfur cluster binding

Iron-sulfur clusters are essential cofactors found in all kingdoms of life and play essential roles in fundamental processes, including but not limited to respiration, photosynthesis, and nitrogen fixation. The chemistry of iron-sulfur clusters makes them ideal for sensing various redox environmental signals, while the physics of iron-sulfur clusters and its host proteins have been long overlooked. One such protein, MagR, has been proposed as a putative animal magnetoreceptor. It forms a rod-like complex with cryptochromes (Cry) and possesses intrinsic magnetic moment. However, the magnetism modulation of MagR remains unknown. Here in this study, iron-sulfur cluster binding in MagR has been characterized. Three conserved cysteines of MagR play different roles in iron-sulfur cluster binding. Two forms of iron-sulfur clusters binding have been identified in pigeon MagR and showed different magnetic properties: [3Fe-4S]-MagR appears to be superparamagnetic and has saturation magnetization at 5 K but [2Fe-2S]-MagR is paramagnetic. While at 300 K, [2Fe-2S]-MagR is diamagnetic but [3Fe-4S]-MagR is paramagnetic. Together, the different types of iron-sulfur cluster binding in MagR attribute distinguished magnetic properties, which may provide a fascinating mechanism for animals to modulate the sensitivity in magnetic sensing.

Mini Review: Advances in 2-Haloacid Dehalogenases

The 2-haloacid dehalogenases (EC 3.8.1.X) are industrially important enzymes that catalyze the cleavage of carbon-halogen bonds in 2-haloalkanoic acids, releasing halogen ions and producing corresponding 2-hydroxyl acids. These enzymes are of particular interest in environmental remediation and environmentally friendly synthesis of optically pure chiral compounds due to their ability to degrade a wide range of halogenated compounds with astonishing efficiency for enantiomer resolution. The 2-haloacid dehalogenases have been extensively studied with regard to their biochemical characterization, protein crystal structures, and catalytic mechanisms. This paper comprehensively reviews the source of isolation, classification, protein structures, reaction mechanisms, biochemical properties, and application of 2-haloacid dehalogenases; current trends and avenues for further development have also been included.