Immobilized metal ion affinity chromatography: a review on its applications

Cytochrome c oxidase oxygen reduction reaction induced by cytochrome c on nickel-coordination surfaces based on graphene oxide in suspension

BACKGROUND

The electrochemical and spectroscopic investigation of bacterial electron-transfer proteins stabilized on solid state electrodes has provided an effective approach for functional respiratory enzyme studies.

METHODS

We assess the biocompatibility of carboxylated graphene oxide (CGO) functionalized with Nickel nitrilotriacetic groups (CGO-NiNTA) ccordinating His-tagged cytochrome c oxidase (CcO) from Rhodobacter sphaeroides.

RESULTS

Kinetic studies employing UV-visible absorption spectroscopy confirmed that the immobilized CcO oxidized horse-heart cytochrome c (Cyt c) albeit at a slower rate than isolated CcO. The oxygen reduction reaction as catalyzed by immobilized CcO could be clearly distinguished from that arising from CGO-NiNTA in the presence of Cyt c and dithiothreitol (DTT) as a sacrificial reducing agent. Our findings indicate that while the protein content is about 3.7‰ by mass with respect to the support, the contribution to the oxygen consumption activity averaged at 56.3%.

CONCLUSIONS

The CGO-based support stabilizes the free enzyme which, while capable of Cyt c oxidation, is unable to carry out oxygen consumption in solution on its own under our conditions. The turnover rate for the immobilized CcO was as high as 240 O₂ molecules per second per CcO unit.

GENERAL SIGNIFICANCE

In vitro investigations of electron flow on isolated components of bacterial electron-transfer enzymes immobilized on the surface of CGO in suspension are expected to shed new light on microbial bioenergetic functions, that could ultimately contribute toward the improvement of performance in living organisms.

Analysis of Complexation Interactions between Metal Ions and Drugs under Pseudo-physiological pH Conditions by a High-throughput Screening Method Using a Solid-phase Extraction Cartridge

A high-throughput screening method for the complexation between metal ions and drugs was established by combining solid-phase extraction (SPE) using a nitrilotriacetic acid (NTA) modified silica spin cartridge with subsequent HPLC analysis. First, a test metal ion solution was passed through the NTA cartridge, then a test drug solution diluted in phosphate buffered saline (pH 7.4) was passed through the metal-chelated NTA cartridge. The complexation behavior between the metal and the drug on the NTA cartridge was evaluated by HPLC quantification of the drug in the SPE eluate. Comprehensive analysis of the complexation behavior between 11 different metal ions and 55 drugs showed that Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺, Cr³⁺ and Fe³⁺ formed complexes with 12, 5, 4, 2, 1 and 1 kinds of drugs, respectively. Bromazepam selectively formed complexes with Cu²⁺, Ni²⁺ and Co²⁺.

Aptamers vs. antibodies as capture probes in optical porous silicon biosensors

Over the past decade aptamers have emerged as a promising class of bioreceptors for biosensing applications with significant advantages over conventional antibodies. However, experimental studies comparing aptasensors and immunosensors, under equivalent conditions, are limited and the results are inconclusive, in terms of benefits and limitations of each bioreceptor type. In the present work, the performance of aptamer and antibody bioreceptors for the detection of a his-tagged protein, used as a model target, is compared. The bioreceptors are immobilized onto a nanostructured porous silicon (PSi) thin film, used as the optical transducer, and the target protein is detected in a real-time and label-free format by reflective interferometric Fourier transform spectroscopy. For the antibodies, random-oriented immobilization onto the PSi nanostructure results in a poor biosensing performance. Contrary, Fc-oriented immobilization of the antibodies shows a similar biosensing performance to that exhibited by the aptamer-based biosensor, in terms of binding rate, dynamic detection range, limit of detection and selectivity. The aptasensor outperforms in terms of its reusability and storability, while the immunosensor could not be regenerated for subsequent experiments.

Current technologies to endotoxin detection and removal for biopharmaceutical purification

Endotoxins are the major contributors to the pyrogenic response caused by contaminated pharmaceutical products, formulation ingredients, and medical devices. Recombinant biopharmaceutical products are manufactured using living organisms, including Gram-negative bacteria. Upon the death of a Gram-negative bacterium, endotoxins (also known as lipopolysaccharides) in the outer cell membrane are released into the lysate where they can interact with and form bonds with biomolecules, including target therapeutic compounds. Endotoxin contamination of biologic products may also occur through water, raw materials such as excipients, media, additives, sera, equipment, containers closure systems, and expression systems used in manufacturing. The manufacturing process is, therefore, in critical need of methods to reduce and remove endotoxins by monitoring raw materials and in-process intermediates at critical steps, in addition to final drug product release testing. This review paper highlights a discussion on three major topics about endotoxin detection techniques, upstream processes for the production of therapeutic molecules, and downstream processes to eliminate endotoxins during product purification. Finally, we have evaluated the effectiveness of endotoxin removal processes from a perspective of high purity and low cost.

Evaluation of Iminodiacetic Acid (IDA) as an Ionogenic Group for Adsorption of IgG1 Monoclonal Antibodies by Membrane Chromatography

Iminodiacetic acid (IDA) is one of the chelating ligands most frequently employed in immobilized metal-ion affinity chromatography (IMAC) due to its ability to act as electron-pair donor, forming stable complexes with intermediate and borderline Lewis metal ions (electron acceptor). Thus, IDA can also be employed in ion exchange chromatography to purify positively charged proteins at neutral pH values. This study aimed to evaluate IDA as an ionogenic group (ion exchanger) immobilized on poly (ethylene vinyl alcohol) (PEVA) hollow fiber membranes for immunoglobulin G₁ (IgG₁) monoclonal antibody (MAb) purification. IDA-PEVA membranes showed considerable promise for MAb purification, since IgG₁ was recovered in eluted fractions with traces of contaminants as confirmed by Western blotting and ELISA analysis. Quantification of IgG₁ showed that a purity of 94.2% was reached in the elution step. Breakthrough curve and batch adsorption experiments showed that the MAb dynamic binding capacity (DBC) of 3.10 mg g^-1 and the maximum adsorption capacity of 70 mg g^-1 were of the same order of magnitude as those found in the literature. The results obtained showed that the IDA-PEVA hollow fiber membrane could be a powerful adsorbent for integrating large-scale processes for purification of MAb from cell culture supernatant.

Challenges and Advances in the Fabrication of Monolithic Bioseparation Materials and their Applications in Proteomics Research

High-performance liquid chromatography integrated with tandem mass spectrometry (HPLC-MS/MS) has become a powerful technique for proteomics research. Its performance heavily depends on the separation efficiency of HPLC, which in turn depends on the chromatographic material. As the "heart" of the HPLC system, the chromatographic material is required to achieve excellent column efficiency and fast analysis. Monolithic materials, fabricated as continuous supports with interconnected skeletal structure and flow-through pores, are regarded as an alternative to particle-packed columns. Such materials are featured with easy preparation, fast mass transfer, high porosity, low back pressure, and miniaturization, and are next-generation separation materials for high-throughput proteins and peptides analysis. Herein, the recent progress regarding the fabrication of various monolithic materials is reviewed. Special emphasis is placed on studies of the fabrication of monolithic capillary columns and their applications in separation of biomolecules by capillary liquid chromatography (cLC). The applications of monolithic materials in the digestion, enrichment, and separation of phosphopeptides and glycopeptides from biological samples are also considered. Finally, advances in comprehensive 2D HPLC separations using monolithic columns are also shown.

Interactions between an amphipathic di-histidine peptide and a metal affinity chromatographic resin derived from a bis(tacn)butane chelating ligand

The interactive behavior of an amphipathic peptide with the Cu²⁺ , Ni²⁺ , and Zn²⁺ complexes of 1,4-bis(triazacyclonon-1-yl)butane), bis(tacn)^but , immobilized onto Sepharose CL-4B, has been investigated. The effects of incubation time, as well as the incubation buffer pH and ionic strength, have been examined. The binding data have been interrogated using Langmuir, Langmuir-Freundlich, bi-Langmuir, and Temkin isothermal models and Scatchard plots. These results confirm that this amphipathic peptide binds with relatively high capacities to the immobilized Cu²⁺ - and Ni²⁺ -1,4-bis(triazacyclonon-1-yl)butane)-Sepharose CL-4B sorbents via at least two discrete sites. However, the corresponding immobilized Zn²⁺ -sorbent had low binding capacity. Moreover, the magnitude of the binding capacities of these sorbents was dependent on the pH and ionic strength of the incubation buffer. These results are relevant to the isolation of E. coli expressed recombinant proteins that incorporate this and related amphipathic peptide tags, containing two or more histidine residues, located at the N- or C-terminus of the recombinant protein, and the co-purification of low abundance host cell proteins of diverse structure, by immobilized metal ion affinity chromatographic methods.

Purification of Recombinant ADAMTSL2

Recombinantly produced proteins are used in many biological disciplines. However, their purity and quality are vital for downstream applications used to determine their structure and functions. Several purification and detection strategies can be used in combination to obtain protein samples with homogeneity and structural conformity. Here we detail the protocols involved in the purification of ADAMTSL2 from mammalian cells. We also describe the protocols used to validate the purity of the protein samples.

Nanoparticle-supported temperature responsive polymer brushes for affinity separation of histidine-tagged recombinant proteins

We developed a modular approach for the preparation of nanoparticle-supported polymer brushes carrying repeating iminodiacetate units for affinity separation of histidine-tagged recombinant proteins. The nanoparticle-supported polymer brushes were prepared via the combination of surface-initiated atom transfer radical polymerization with Cu(I)-catalyzed azide-alkyne cycloaddition reaction. The nanocomposite materials were characterized to determine the particle size, morphology, organic content, densities of polymer chains and the affinity ligand. Protein binding assay illustrated that the iminodiacetate-rich polymer brushes enable to selectively bind histidine-tagged recombinant proteins in the presence of abundant interfering proteins. More importantly, the protein binding capacity can be tuned by adjusting the environmental temperature. STATEMENT OF SIGNIFICANCE: The nanoparticle core-polymer brush structure enables selective binding of histidine-tagged recombinant proteins via multiple metal-coordination interactions. The soft and flexible structure of the polymer brushes was found beneficial for lowering the steric hindrance in protein binding. Taking advantage of the conformational changes of the polymer brushes at different temperatures, it is possible to modulate the protein binding on the nanocomposite by adjusting the environmental temperature. In general, the iminodiacetate-rich core-brush nano adsorbents are attractive for purifying histidine-tagged recombinant proteins practically. The synthetic approach reported here may be expanded to develop other advanced functional materials for applications in various biomedical fields ranging from biosensors to drug delivery.

Promiscuity of host cell proteins in the purification of histidine tagged recombinant xylanase A by IMAC procedures: A case study with a Ni2+-tacn-based IMAC system

Determination of the extent of host cell protein (HCP) contamination is an essential pre-requisite to validate the chromatographic purification of recombinant proteins. This study explores how different experimental conditions affect the HCP profiles generated during the immobilised metal ion affinity chromatographic (IMAC) purification with a Ni²⁺-1,4,7-triaza-cyclononane (tacn) Sepharose FF™ sorbent of the Bacillus halodurans N- and C-terminal His₆-tagged xylanase A, expressed by Escherichia coli BL21(DE3) cells, and captured directly from cell lysates. Comparative studies were also carried out under identical loading, wash and elution conditions using nitrilotriacetic acid (NTA), also immobilised onto an agarose support and complexed with Ni²⁺ ions. High-resolution tandem mass spectrometry of the tryptic peptides derived from the proteins present in the IMAC flow-through, wash and elution fractions confirmed that the E. coli BL21(DE3) HCP profiles were dependent on the choice of adsorbent. With feedstocks containing the N- or C-terminal His₆-tagged xylanase A, in several instances the same E. coli BL21(DE3) HCPs were found to co-elute with the tagged protein from either adsorbent, indicating a preferential ability of some HCPs to bind to both the IMAC resin and to the recombinant protein. This promiscuous behaviour has been found to be due to factors other than just the presence of histidine-rich motifs within the amino acid sequences of these HCPs. This case study demonstrates that the choice of protein expression and separation conditions impact on the levels of HCP contamination when different IMAC systems are employed.

Cost-effective production of tag-less recombinant protein in Nicotiana benthamiana

Plants have recently received a great deal of attention as a means of producing recombinant proteins. Despite this, a limited number of recombinant proteins are currently on the market and, if plants are to be more widely used, a cost-effective and efficient purification method is urgently needed. Although affinity tags are convenient tools for protein purification, the presence of a tag on the recombinant protein is undesirable for many applications. A cost-effective method of purification using an affinity tag and the removal of the tag after purification has been developed. The family 3 cellulose-binding domain (CBM3), which binds to microcrystalline cellulose, served as the affinity tag and the small ubiquitin-related modifier (SUMO) and SUMO-specific protease were used to remove it. This method, together with size-exclusion chromatography, enabled purification of human interleukin-6 (hIL6) with a yield of 18.49 mg/kg fresh weight from leaf extracts of Nicotiana benthamiana following Agrobacterium-mediated transient expression. Plant-produced hIL6 (P-hIL6) contained less than 0.2 EU/μg (0.02 ng/mL) endotoxin. P-hIL6 activated the Janus kinase-signal transducer and activator of transcriptional pathways in human LNCaP cells, and induced expression of IL-21 in activated mouse CD4+ T cells. This approach is thus a powerful method for producing recombinant proteins in plants.

Expression of recombinant tachyplesin I in Pichia pastoris

The development of antibiotic-resistant bacteria has become a major public health problem, prompting the search for alternative solutions. Tachyplesin I (TP-I) is an antimicrobial peptide, which exhibits potent and broad-spectrum activities against bacteria, fungi, viruses, and tumor cells. However, limited amounts of TP-I produced in horseshoe crab restrict its large-scale use. In order to solve this problem, a eukaryotic expression system of Pichia pastoris with high TP-I expression was constructed by gene engineering. To achieve high expression of TP-I, 74 amino acid-long peptide (4TP-1) was designed containing 4 copies of TP-I, and specific cleavage sites for pancreatic elastase (-Ala↓ or -Gly↓) and carboxypeptidase A (cleaves C terminal amino acid); these cleavage sites for enzymes were located between the four copies of TP-I. The gene sequence for the designed peptide was synthesized taking into consideration codon preferences for P. pastoris, and cloned into the highly efficient expression vector pGAPZα B. Host Pichia pastoris strain GS115 cells were transfected by the constructed expression vector pGAPZα B-4tp-I by electroporation. Tricine-SDS-PAGE electrophoresis was carried out to detect the expression of target peptides in the fermentation medium. This analysis showed a protein band of 3.3 kDa, identical to that of chemically synthesized TP-I, verifying that successful synthesis and secretion of TP-I by genetically engineered P. pastoris. The concentration of TP-I in the fermentation broth was 27.24-29.53 mg/L. High-resolution mass spectrometry analysis documented that the TP-I monomer had the same molecular weight, 2262.85, as the designed 17-amino acid sequence. The recombinant TP-I peptide displayed different levels of bactericidal activity against Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus. Thus, the present study demonstrated the feasibility of achieving high levels of expression of TP-I in P. pastoris.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

Infectious diseases claim millions of lives each year. Robust and accurate diagnostics are essential tools for identifying those who are at risk and in need of treatment in low-resource settings. Inorganic complexes and metal-based nanomaterials continue to drive the development of diagnostic platforms and strategies that enable infectious disease detection in low-resource settings. In this review, we highlight works from the past 20 years in which inorganic chemistry and nanotechnology were implemented in each of the core components that make up a diagnostic test. First, we present how inorganic biomarkers and their properties are leveraged for infectious disease detection. In the following section, we detail metal-based technologies that have been employed for sample preparation and biomarker isolation from sample matrices. We then describe how inorganic- and nanomaterial-based probes have been utilized in point-of-care diagnostics for signal generation. The following section discusses instrumentation for signal readout in resource-limited settings. Next, we highlight the detection of nucleic acids at the point of care as an emerging application of inorganic chemistry. Lastly, we consider the challenges that remain for translation of the aforementioned diagnostic platforms to low-resource settings.

Overview of Characterizing Cancer Glycans with Lectin-Based Analytical Methods

Glycosylation is a post-translational modification that is often altered in disease development and progression, including cancer. In cancerous patients, the abnormal expression of glycosylation enzymes leads to aberrant glycosylation, which has been linked to malignant tissues. Due to aberrant glycosylation, the presence of specific glycans can be used as biomarkers for identifying the type and stage of cancer. Glycan structures are heterogeneous, with different protein glycoforms having different functional activities. Lectins are an important tool in glycan analysis due to their specificity in binding to unique glycan linkages and monosaccharide units, which allows for the identification of unique glycan structural properties. In this review, we will discuss the use of lectins in microarrays and chromatography for characterizing glycan structures.

Size of Protein is a Major Factor that Affects Retention on Preparative IMAC Columns

Immobilized metal affinity chromatography (IMAC) is a specific high-capacity technique used in large-scale purification of proteins. IMAC exploits the ability of immobilized metal ions to form coordination bonds with atoms in the side chains of certain amino acids. The technique is generally robust. However, several factors still affect column binding capacity, retention, yield and purity of proteins during IMAC. It was observed that the recovery of 6× histidine, (His)₆-tagged proteins from metal affinity columns differ significantly depending on the size of the protein. To test this observation, we determined the effect of protein size, flow-rate, number and position of (His)₆ tag on the retention of highly expressing proteins on commercial Ni²⁺ and Co²⁺ IMAC columns. All experiments were performed in phosphate buffer to eliminate interference of amine-containing buffers with the binding of the (His)₆ tag to the columns. Column retention was determined as the ratio of protein of interest in the supernatant (input) to flow-through (output). Data obtained suggest that regardless of the flow-rate, (His)₆ tag position and number, the size of protein is a major factor affecting column retention and therefore recovery during column IMAC purification. Small and medium-sized proteins (~ 50 kDa) have higher column retention than bigger proteins, resulting in higher recovery. These outcomes provide important information to consider when performing IMAC.

Process for production and purification of Lethal Toxin Neutralizing Factor (LTNF) from E. coli and its economic analysis

BACKGROUND

Purification of peptides offers unique challenges with respect to obtaining the desired process yield and selectivity. Lethal Toxin Neutralizing Factor (LTNF) is a peptide that is known to neutralize snake venom in mice when the peptide is preincubated with the venom prior to intravenous injection. A process for producing highly purified recombinant LTNF has been developed. The process has been modelled in SuperPro designer using laboratory data for a plant capable of producing 10 Kg of purified rLTNF. Economic analysis has been performed for manufacturing 3 ton of purified rLTNF.

RESULTS

The process developed produces peptide in the form of concatemer that has been specifically designed to accumulate as insoluble inclusion bodies (IB) during expression in E. coli. A cation exchange chromatography step has been developed to capture the rLTNF concatemer at 140 g/L dynamic binding capacity. Further, the purified concatemer is cleaved completely into monomeric rLTNF using alpha-chymotrypsin enzyme. Finally, a reversed phase high performance liquid chromatography has been designed to purify rLTNF with a recovery of more than 90% and purity greater than 98%. The overall process recovery is 78±2% resulting in 3.36 g of purified product per batch. Techno-economic evaluation of the process has been performed to demonstrate its economic feasibility against currently marketed antivenom products.

CONCLUSIONS

The developed process is able to produce purified rLTNF with 78±2% recovery. The study shows that recombinant technology can be used to produce rLTNF cost effectively and shows potential as a substitute for currently available antivenoms against snakebite.

Assessing histidine tags for recruiting deoxyribozymes to catalyze peptide and protein modification reactions

We evaluate the ability of hexahistidine (His6) tags on peptide and protein substrates to recruit deoxyribozymes for modifying those substrates. For two different deoxyribozymes, one that creates tyrosine-RNA nucleopeptides and another that phosphorylates tyrosine side chains, we find substantial improvements in yield, kobs, and Km for peptide substrates due to recruiting by His6/Cu(2+). However, the recruiting benefits of the histidine tag are not observed for larger protein substrates, likely because the tested deoxyribozymes either cannot access the target peptide segments or cannot function when these segments are presented in a structured protein context.

Affinity induced immobilization of adenylate cyclase from the crude cell lysate for ATP conversion

The development of an orientation immobilization technique via affinity between polyhistidine tags and metal ions aims at maintaining biocatalytic activity of the enzymes. In this work, to tackle the issue of the immobilization of adenylate cyclase (AC), a simple and effective approach of synthesizing iminodiacetic acid (IDA)-Ni²⁺ particles was applied for simultaneously purifying and immobilizing his-tagged AC. We chose agarose particles as carriers, and then decorated them with IDA, leading to the formation of a coordination combination of Ni²⁺. The porous carriers with a large pore size of 50 nm and a specific surface area of 45.8 m²/g exhibited favorable enzymatic activity and loading capacity. The optimal pH of the immobilized enzyme increased from 8.0 to 9.0 and the optimal temperature increased from 30 °C to 35 °C, compared to the free AC. Moreover, the immobilized AC retained a residual activity of approximately 80% after storing it at 25 °C for 48 h, whereas only 40% of the activity was left in the free AC at the same conditions. Maximum yield of cyclic adenosine-3', 5'- monophosphate (cAMP) reached up to the summit of the reaction. The immobilized AC by affinity adsorption will provide a promising route for the industrial production of cAMP.

Affinity functionalization of PVA-co-PE nanofibrous membrane with Ni(ii)-chelated ligand for bovine hemoglobin adsorption

Ni(ii)-Chelated PVA-co-PE nanofibrous membrane can be prepared easily and this study provides an exploratory research for the large-scale purification of BHb.

Development of immobilized Sn4+ affinity chromatography material for highly selective enrichment of phosphopeptides

In this work, we first immobilized tin(IV) ion on polydopamine-coated magnetic graphene (magG@PDA) to synthesize Sn⁴⁺ -immobilized magG@PDA (magG@PDA-Sn⁴⁺ ) and successfully applied the material to highly selective enrichment of phosphopeptides. The material gathered the advantages of large surface area of graphene, superparamagnetism of Fe₃ O₄ , good hydrophilicity and biocompatibility of polydopamine, and strong interaction between Sn⁴⁺ and phosphopeptides. The enrichment performance of magG@PDA-Sn⁴⁺ toward phosphopeptides from digested β-casein at different concentrations, with and without added digested BSA was investigated and compared with magG@PDA-Ti⁴⁺ . The results showed high selectivity and sensitivity of the Sn⁴⁺ -IMAC material toward phosphopeptides, as good as the Ti⁴⁺ -IMAC material. Finally, magG@PDA-Sn⁴⁺ was applied to the analysis of endogenous phosphopeptides from a real sample, human saliva, with both MALDI-TOF MS and nano-LC-ESI-MS/MS. The results indicated that the as-synthesized Sn⁴⁺ -IMAC material not only has good enrichment performance, but also could serve as a supplement to the Ti⁴⁺ -IMAC material and expand the phosphopeptide coverage enriched by the single Ti⁴⁺ -IMAC material, demonstrating the broad application prospects of magG@PDA-Sn⁴⁺ in phosphoproteome research.

New Interface for Purification of Proteins: One-Dimensional TiO2 Nanotubes Decorated by Fe3O4 Nanoparticles

In this work, a high surface area interface, based on anodic one-dimensional (1D) TiO₂ nanotubes homogeneously decorated by Fe₃O₄ nanoparticles (TiO₂NTs@Fe₃O₄NPs) is reported for the first time for an unprecedented purification of His-tagged recombinant proteins. Excellent purification results were achieved from the model protein mixture, as well as from the whole cell lysate (with His-tagged ubiquitin). Compared to a conventional immobilized-metal affinity chromatography (IMAC) system, specific isolation of selected His-tagged proteins on behalf of other proteins was significantly enhanced on TiO₂NTs@Fe₃O₄NPs interface under optimized binding and elution conditions. The combination of specific isolation properties, magnetic features, biocompatibility, and ease of preparation of this material consisting of two basic metal oxides makes it a suitable candidate for future purification of recombinant proteins in biotechnology. The principally new material bears a large potential to open new pathways for discoveries in nanobiotechnology and nanomedicine.

Integrative approach for the analysis of the proteome-wide response to bismuth drugs in Helicobacter pylori

An integrative metalloproteomic approach to unveil the role of antimicrobial metals in general using bismuth as an example.

Bismuth drugs, despite being clinically used for decades, surprisingly remain in use and effective for the treatment of Helicobacter pylori infection, even for resistant strains when co-administrated with antibiotics. However, the molecular mechanisms underlying the clinically sustained susceptibility of H. pylori to bismuth drugs remain elusive. Herein, we report that integration of in-house metalloproteomics and quantitative proteomics allows comprehensive uncovering of the bismuth-associated proteomes, including 63 bismuth-binding and 119 bismuth-regulated proteins from Helicobacter pylori, with over 60% being annotated with catalytic functions. Through bioinformatics analysis in combination with bioassays, we demonstrated that bismuth drugs disrupted multiple essential pathways in the pathogen, including ROS defence and pH buffering, by binding and functional perturbation of a number of key enzymes. Moreover, we discovered that HpDnaK may serve as a new target of bismuth drugs to inhibit bacterium-host cell adhesion. The integrative approach we report, herein, provides a novel strategy to unveil the molecular mechanisms of antimicrobial metals against pathogens in general. This study sheds light on the design of new types of antimicrobial agents with multiple targets to tackle the current crisis of antimicrobial resistance.

Catalase purification from rat liver with iron-chelated poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) cryogel discs

In this study, iron-chelated poly(hydroxyethyl methacrylate-N-methacryloyl-(l)-glutamic acid) (PHEMAGA/Fe(3+)) cryogel discs were prepared. The PHEMAGA/Fe(3+) cryogel discs were characterized by elemental analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, swelling tests, and surface area measurements. The PHEMAGA/Fe(3+) cryogel discs had large pores ranging from 10 to 100 µm with a swelling degree of 9.36 g H2O/g cryogel. Effects of pH, temperature, initial catalase concentration, and flow rate on adsorption capacity of the PHEMAGA/Fe(3+) cryogel discs were investigated. Maximum catalase adsorption capacity (62.6 mg/g) was obtained at pH 7.0, 25°C, and 3 mg/ml initial catalase concentration. The PHEMAGA/Fe(3+) cryogel discs were also tested for the purification of catalase from rat liver. After tissue homogenization, purification of catalase was performed using the PHEMAGA/Fe(3+) cryogel discs and catalase was obtained with a yield of 54.34 and 16.67 purification fold.

T7 Endonuclease I Mediates Error Correction in Artificial Gene Synthesis

Efficacy of de novo gene synthesis largely depends on the quality of overlapping oligonucleotides used as template for PCR assembly. The error rate associated with current gene synthesis protocols limits the efficient and accurate production of synthetic genes, both in the small and large scales. Here, we analysed the ability of different endonuclease enzymes, which specifically recognize and cleave DNA mismatches resulting from incorrect impairments between DNA strands, to remove mutations accumulated in synthetic genes. The gfp gene, which encodes the green fluorescent protein, was artificially synthesized using an integrated protocol including an enzymatic mismatch cleavage step (EMC) following gene assembly. Functional and sequence analysis of resulting artificial genes revealed that number of deletions, insertions and substitutions was strongly reduced when T7 endonuclease I was used for mutation removal. This method diminished mutation frequency by eightfold relative to gene synthesis not incorporating an error correction step. Overall, EMC using T7 endonuclease I improved the population of error-free synthetic genes, resulting in an error frequency of 0.43 errors per 1 kb. Taken together, data presented here reveal that incorporation of a mutation-removal step including T7 endonuclease I can effectively improve the fidelity of artificial gene synthesis.

PET imaging of 64Cu-DOTA-scFv-anti-PSMA lipid nanoparticles (LNPs): Enhanced tumor targeting over anti-PSMA scFv or untargeted LNPs

INTRODUCTION

Single chain (scFv) antibodies are ideal targeting ligands due to their modular structure, high antigen specificity and affinity. These monovalent ligands display rapid tumor targeting but have limitations due to their fast urinary clearance.

METHODS

An anti-prostate membrane antigen (PSMA) scFv with a site-specific cysteine was expressed and evaluated in a prostate cancer xenograft model by Cu-64 PET imaging. To enhance tumor accumulation, the scFv-cys was conjugated to the co-polymer DSPE-PEG-maleimide that spontaneously assembled into a homogeneous multivalent lipid nanoparticle (LNP).

RESULTS

The targeted LNP exhibited a 2-fold increase in tumor uptake compared to the scFv alone using two different thiol ester chemistries. The anti-PSMA scFv-LNP exhibited a 1.6 fold increase in tumor targeting over the untargeted LNP.

CONCLUSIONS

The targeted anti-PSMA scFv-LNP showed enhanced tumor accumulation over the scFv alone or the untargeted DOTA-micelle providing evidence for the development of this system for drug delivery.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

Anti-tumor scFv antibody fragments have not achieved their therapeutic potential due to their fast blood clearance. Conjugation to an LNP enables multivalency to the tumor antigen as well as increased molecular size for chemotherapy drug delivery.

Structure-Based Design and Synthesis of a New Phenylboronic-Modified Affinity Medium for Metalloprotease Purification

Metalloproteases are emerging as useful agents in the treatment of many diseases including arthritis, cancer, cardiovascular diseases, and fibrosis. Studies that could shed light on the metalloprotease pharmaceutical applications require the pure enzyme. Here, we reported the structure-based design and synthesis of the affinity medium for the efficient purification of metalloprotease using the 4-aminophenylboronic acid (4-APBA) as affinity ligand, which was coupled with Sepharose 6B via cyanuric chloride as spacer. The molecular docking analysis showed that the boron atom was interacting with the hydroxyl group of Ser176 residue, whereas the hydroxyl group of the boronic moiety is oriented toward Leu175 and His177 residues. In addition to the covalent bond between the boron atom and hydroxyl group of Ser176, the spacer between boronic acid derivatives and medium beads contributes to the formation of an enzyme-medium complex. With this synthesized medium, we developed and optimized a one-step purification procedure and applied it for the affinity purification of metalloproteases from three commercial enzyme products. The native metalloproteases were purified to high homogeneity with more than 95% purity. The novel purification method developed in this work provides new opportunities for scientific, industrial and pharmaceutical projects.

Affinity chromatography: A versatile technique for antibody purification

Antibodies continue to be extremely utilized entities in myriad applications including basic research, imaging, targeted delivery, chromatography, diagnostics, and therapeutics. At production stage, antibodies are generally present in complex matrices and most of their intended applications necessitate purification. Antibody purification has always been a major bottleneck in downstream processing of antibodies, due to the need of high quality products and associated high costs. Over the years, extensive research has focused on finding better purification methodologies to overcome this holdup. Among a plethora of different techniques, affinity chromatography is one of the most selective, rapid and easy method for antibody purification. This review aims to provide a detailed overview on affinity chromatography and the components involved in purification. An array of support matrices along with various classes of affinity ligands detailing their underlying working principles, together with the advantages and limitations of each system in purifying different types of antibodies, accompanying recent developments and important practical methodological considerations to optimize purification procedure are discussed.

Electrostatic Deflection of a Molecular Beam of Massive Neutral Particles: Fully Field-Oriented Polar Molecules within Superfluid Nanodroplets

Electric deflection measurements on liquid helium nanodroplets doped with individual polar molecules demonstrate that the cold superfluid matrix enables full orientation of the molecular dipole along the external field. This translates into a deflection force that is increased enormously by comparison with typical deflection experiments, and it becomes possible to measurably deflect neutral doped droplets with masses of tens to hundreds of thousands of Daltons. By using continuous fluxes of fully oriented polar molecules and measuring the deflection of the doped nanodroplet beam, this approach makes it possible to directly determine the dipole moments of internally cryogenically cold molecules. The technique is broadly and generally applicable, including to complex and biological molecules.