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This document is a table that provides information on various proteins and their characteristics. The proteins listed are associated with different plants and may have implications for allergies and sensitivities. The study found that patients sensitized to Ligustrum pollen who were also sensitized to Fraxinus exhibited a different pattern of allergen recognition compared to those without Fraxinus sensitization. The study was supported by the National Institute of Respiratory Diseases Ismael Cosío Villegas in Mexico. Further research is needed to validate the role of these proteins in respiratory allergies. [Extracted from the article]

The elution by imidazole is used in the purification process of non-alpha IL-2 mutein, specifically in the immobilized metal chelates affinity chromatography step (IMAC). In order to demonstrate that a new elution process is possible using cheaper solutions, changes were made in the former capture step. These changes consist on separate the size exclusion chromatography and the controlled oxidation stage which are currently performed together, as well as changing the elution solution. To achieve this, a 22 factorial design of experiments was performed to evaluate the effect of pH and molar concentration on recovery, purity, and particle diameter. The best results were obtained with the solution of sodium acetate 20 mmol L-1 pH 4 being similar to those obtained in the industry nowadays: 29 % recovery, 90 % of purity, and particle diameter 18,40 nm. The first contribution of this paper is to demonstrate the feasibility of using the new elution methodology. Moreover, by using the academic software SuperPro Designer, the actual capture step of the purification process (elution by Imidazole) was simulated, validated, and verified. To demonstrate the relationship between costs and benefits, the CH SFF matrix gel volume was incremented. This change increased costs at this stage. However, the productivity obtained grew to 109 mg h-1, 2.78 times greater than the current productivity. Therefore, the gross net increased by 879 325, 00 $. This result constitutes the second contribution of this paper. [ABSTRACT FROM AUTHOR]

Background: Traditional bioethanol fermentation industries are not operated under strict sterile conditions and are prone to microbial contamination. Lactic acid bacteria (LAB) are often pervasive in fermentation tanks, competing for nutrients and producing inhibitory acids that have a negative impact on ethanol-producing yeast, resulting in decreased yields and stuck fermentations. Antibiotics are frequently used to combat contamination, but antibiotic stewardship has resulted in a shift to alternative antimicrobials. Results: We demonstrate that endolysin LysMP, a bacteriophage-encoded peptidoglycan hydrolase, is an effective method for controlling growth of LAB. The LysMP gene was synthesized based on the prophage sequence in the genome of Limosilactobacillus fermentum KGL7. Analysis of the recombinant enzyme expressed in E. coli and purified by immobilized metal chelate affinity chromatography (IMAC) showed an optimal lysis activity against various LAB species at pH 6, with stability from pH 4 to 8 and from 20 to 40 °C up to 48 h. Moreover, it retains more than 80% of its activity at 10% ethanol (v/v) for up to 48 h. When LysMP was added at 250 µg/mL to yeast corn mash fermentations containing L. fermentum, it reduced bacterial load by at least 4-log fold compared to the untreated controls and prevented stuck fermentation. In comparison, untreated controls with contamination increased from an initial bacterial load of 1.50 × 107 CFU/mL to 2.25 × 109 CFU/mL and 1.89 × 109 CFU/mL after 24 h and 48 h, respectively. Glucose in the treated samples was fully utilized, while untreated controls with contamination had more than 4% (w/v) remaining at 48 h. Furthermore, there was at least a fivefold reduction in lactic acid (0.085 M untreated contamination controls compared to 0.016 M treated), and a fourfold reduction in acetic acid (0.027 M untreated contamination controls vs. 0.007 M treated), when LysMP was used to treat contaminated corn mash fermentations. Most importantly, final ethanol yields increased from 6.3% (w/v) in untreated contamination samples to 9.3% (w/v) in treated contamination samples, an approximate 50% increase to levels comparable to uncontaminated controls 9.3% (w/v). Conclusion: LysMP could be a good alternative to replace antibiotics for mitigation of LAB contamination in biofuel refineries. [ABSTRACT FROM AUTHOR]

Camel is continually exposed to stressful desert environment that enhances generation of reactive oxygen species, including hydrogen peroxide (H2O2). Catalase plays an important role in detoxification of H2O2. A highly active catalase from camel kidney was purified to homogeneity, with a specific activity of 1,774,392 U/mg protein, using ion exchange and metal chelate affinity chromatography. The molecular weight of the enzyme was 268 kDa consisting of four identical subunits of 63 kDa. The enzyme showed higher optimum temperature (45 °C) and higher activation energy (4.37 kJ mol−1). The thermodynamic parameters, ΔH, ΔG and ΔS, were determined. The effect of various metal ions and chemicals on enzyme activity was investigated. Km, Vmax, kcat and kcat/Km values for H2O2 were found to be 46 mM, 10,715,045 U/mg, 48,265,968 s−1 and 2,966,562 s−1 mM−1, respectively. Camel kidney catalase displayed higher affinity efficiency for H2O2 and can protect reduced glutathione (GSH) from oxidation by H2O2. Sodium azide was found to be a noncompetitive inhibitor of enzyme with Ki and IC50 of 17.88 µM and 20.94 µM, respectively. Camel catalase showed unique biochemical properties. Interestingly, camel catalase can protect molecules (GSH) and organ functions (kidney) from the toxic effects of H2O2 induced by stressful desert environment. [ABSTRACT FROM AUTHOR]

Background: Levofloxacin is a third-generation fluoroquinolone that has several advantages over its (R) ofloxacin isomer. It is used to treat different types of infection, including urinary infection and prostatitis. Objective: A new HPLC method for the enantioselective separation of levofloxacin and its chiral impurity was developed and validated to improve the separation of the enantiomers of levofloxacin [impurity(R) and active principle (S)] by increasing the value of the resolution between the eutomer and the distomer. Method: Chromatographic separation was performed on a Prodigy ODS -2, 5 µm 4.6 x 150 mm column, with a gradient of buffer solution and methanol (80:20, v/v). A Box-Behnken design was considered when optimizing the enantioseparation involving the effects of many factors such as the concentration of d-phenylalanine, the pH of the buffer, the percentage of organic modifier in the mobile phase, the flow rate, the temperature of the column, and the type of column. Results: Chiral separation was achieved with an optimal resolution of 3.8. The method was successfully validated following the International Conference on Harmonization Q2 (R1) guideline, fulfilling the acceptance criteria for selectivity [no interference in the retention time of (S) levofloxacin and (R) levofloxacin], linearity (r ≥0.999 in the range 1.25-3.75 µg/mL for all enantiomers), and precision (RSD <2%). Accuracy was assessed by the application of the analytical method to an analyte of known purity, providing evidence for the usefulness of this monitoring system. Conclusions: The method was successfully used for the determination of levofloxacin impurity in raw material and pharmaceutical dosage forms. Highlights: The following method is accurate and robust to quantify and characterize the presence of levofloxacin impurity in raw material for pharmaceutical compounds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Peptide–Ca complexes can promote Ca absorption. The present study aimed to determine the transport mechanism and structural characteristics of sunflower seed and peanut peptides with high Ca binding capacity with respect to developing third‐generation Ca supplements and functional food ingredients. RESULTS: High Ca‐binding fractions of 1–3 kDa sunflower seed peptide (SSP4) and ≥ 10 kDa peanut peptide (PP1) had higher amount of Ca transported than CaCl2 and two hydrolyzed proteins in Caco‐2 cells. SSP4 and PP1 were separated by Ca ion metal chelate affinity chromatography, and high Ca‐binding fractions were observed for SSP4‐P2 and PP1‐P2. The amino acid sequences of SSP4‐P2 and PP1‐P2 were characterized by high‐performance liquid chromatography‐electrospray ionization‐time of flight mass spectrometry. Seven and eight peptides were identified from SSP4‐P2 and PP1‐P2, respectively. These peptides had molecular weights ranging from 1500 Da to 2500 Da and a large number of characteristic amino acid sequences, such as EEEQQQ, EQ–QQQ–QQ, QQ–QQQQQ, E–EEE, EE–EEQ, RR, Q–QQ–QQQ, EE–EQ–EE–Q, QQ–QQQQ, and Q–QQQQ, where 'E' is glutamic acid and 'Q' is glutamine. CONCLUSION: SSP4 and PP1 can promote Ca transport in Caco‐2 cells without affecting cell permeability. The amino acid sequences of SSP4‐P2 and PP1‐P2 with high Ca‐binding abilities contain characteristic sequences, such as continuous glutamic acid and glutamine, and have low molecular weights. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Alditols are potential chemical markers in traditional Chinese medicine for quality control purpose. For example, mannitol is one of the major compounds in Cordyceps sinensis. Galactitol is the proposed marker compound of formulated oral traditional Chinese medicine liquid "Fufangfufangteng Heji." Development of a highly selective analytical method for unambiguous identification of selected alditols is of prime importance to assure the quality of these valued and precious traditional Chinese medicines. In this study, a liquid chromatography–tandem mass spectrometry method based on ligand exchange chromatography was developed to analyze and identify underivatized alditols such as galactitol, mannitol and sorbitol in different traditional Chinese medicines. The limits of detection of these alditols ranged from 0.7 to 1.4 mg/kg. The limits of quantification of these alditols ranged from 2.3 to 4.6 mg/kg. The method has been applied in the detection of alditols in various samples such as Cordyceps sinensis, Cordyceps militaris, and concentrated granule of Radix Celastrus orbiculatus. The results indicated that several underivatized alditols could be identified rapidly and unambiguously by liquid chromatography–tandem mass spectrometry on ligand exchange chromatography column. [ABSTRACT FROM AUTHOR]

The article discusses axon regeneration constitutes a fundamental challenge for regenerative neurobiology, necessitates the use of tailor-made biomaterials for controllable delivery of cells and biomolecules. Topics include the B12-dependent photoreceptor protein CarHC has complex with transition metal ions for an amino-terminal His6-tag; and methods for protein conjugation and assembly have opened a venue to diverse bioactive protein hydrogels.

The article explores the enzymatic mechanism of Legionella effector, AnkX and the family of filamentation induced by cyclic adenosine monophosphate (FIC) proteins. It discusses about the causative agent of Legionnaires disease, Legionella pneumophila, translocate the phosphocholine transferase AnkX during infection and thereby post translationally modifies the small guanosine triphosphatase (GTPase) Rab1.

The bacteria utilizing methane as a growth substrate (methanotrophs) are important constituents of the biosphere. Methanotrophs mitigate the emission of anthropogenic and natural greenhouse gas methane to the environment and are the promising agents for future biotechnologies. Many aspects of CH4 bioconversion by methanotrophs require further clarification. This study was aimed at characterizing the biochemical properties of the malic enzyme (Mae) from the halotolerant obligate methanotroph Methylotuvimicrobium alcaliphilum 20Z. The His6-tagged Mae was obtained by heterologous expression in Escherichia coli BL21 (DE3) and purified by affinity metal chelating chromatography. As determined by gel filtration and non-denaturating gradient gel electrophoresis, the molecular mass of the native enzyme is 260 kDa. The homotetrameric Mae (65x4 kDa) catalyzed an irreversible NAD+-dependent reaction of L-malate decarboxylation into pyruvate with a specific activity of 32 ± 2 units mg-1 and Km value of 5.5 ± 0.8 mM for malate and 57 ± 5 μM for NAD+. The disruption of the mae gene by insertion mutagenesis resulted in a 20-fold increase in intracellular malate level in the mutant compared to the wild type strain. Based on both enzyme and mutant properties, we conclude that the malic enzyme is involved in the control of intracellular L-malate level in Mtm. alcaliphilum 20Z. Genomic analysis has revealed that Maes present in methanotrophs fall into two different clades in the amino acid-based phylogenetic tree, but no correlation of the division with taxonomic affiliations of the host bacteria was observed. [ABSTRACT FROM AUTHOR]

Compared to patients' health conditions in the previous year, over 70% of patients (17 out of 23, 9 missing values) rated their health condition after HDM-SCIT initiation with "notably improved" (30%) or "slightly improved" (44%) despite symptom evaluation taking place after only 5 injections (4350 SU administered), and 22% of patients with "unchanged". During the primary evaluation period, in the 1262 evaluable patients for this analysis (300IR n = 586, placebo n = 676), PSCD2-0 was significantly higher in patients treated with 300IR HDM tablet compared with patients receiving placebo (31.8% versus 25.4%; I P i = I i 0.0082). Statistically significant improvements in the disease severity score SCORAD, patient self-reported disease severity score POEM, Staphylococcus Aureus colonization status, and log-transformed blood IgE level were found when patients experienced pine-tar bathing compared with vehicle bathing. We investigated 1) the prevalence of uncontrolled asthma among children referred for asthma and children referred for atopic diseases other than asthma (i.e. food allergy, allergic rhinitis, atopic dermatitis) to secondary care; 2) the predictors associated with uncontrolled asthma. When analysing the results by number of simultaneously recognized HDM, HK patients sensitizations were largely prevailing vs IT patients for high number of simultaneous HDM sensitization (11 vs 8), whilst the opposite was recorded for IT vs HK patients for lower number of simultaneous HDM sensitization (1 to 4). [Extracted from the article]

Abstract Utilizing block copolymers as coatings, a protocol of chiral ligand exchange capillary electrochromatography (CLE-CEC) protocol was designed and developed with dual ligands for D,L-amino acids enantioseparation. Four block copolymers including poly maleic anhydride- co -styrene- co -N-methacryloyl- L -histidine methyl ester [P(MAn-St-MAH)], poly maleic anhydride- co -styrene- co -N-methacryloyl- L -lysine methyl ester [P(MAn-St-MAL)], poly maleic anhydride- co -styrene- co -N-methacryloyl- L -phenylalanine methyl ester [P(MAn-St-MAP)] and poly maleic anhydride- co -styrene- co -N-methacryloyl- L -threonine methyl ester [P(MAn-St-MAT)] were synthesized by reversible addition fragmentation chain transfer polymerization reaction. Key factors affecting the enantioresolution were optimized, including the concentration of Zn (II) central ion, pH value of buffer solution and monomers of the block copolymers. The enantioresolution of the proposed CLE-CEC system could be enhanced dramatically by employing P(MAn-St-MAH) as the immobilized chiral ligand and by coordinating the synergistic effect of free ligand in buffer solution. The principle of improved enantioresolution of the CLE-CEC system with dual ligands was discussed. Well enantioseparation was successfully realized with 7 pairs of D,L-amino acids enantiomers baseline separation and 5 pairs part separation. For quantitative analysis of D, L -alanine, a good linearity was established in the range of 9.4 μM to 1.5 mM (r2 = 0.997) with the limits of detection (LODs) 3.7 μM of D -alanine, 2.0 μM for L -alanine, and limits of quantification (LOQs) 9.0 μM for D -alanine and 6.0 μM for L -alanine. The peak area and migration time reproducibility (n = 6) were 4.1% and 3.5% for D -alanine, 3.7% and 3.1% for L -alanine. Further, the enzyme kinetics study of alanine aminotransferase was investigated with the constructed CLE-CEC system. Graphical abstract fx1 Highlights • Block copolymers were synthesized and used as the immobilized ligands. • A CLE-CEC protocol was developed for enantioseparation of D,L-AAs with dual ligands. • The proposed CLE-CEC system displayed obvious improved chiral separation resolution. [ABSTRACT FROM AUTHOR]

Abstract Synthesis and structural characterization of three new isomorphous coordination compounds, fabricated from CdHal 2 (Hal = Cl, Br, I) and a bulky helical organic ligand 1,2-diphenyl-1,2-bis((phenyl(pyridin-2-yl)methylene)hydrazono)ethane (L), namely [CdHal 2 L] (Hal = Cl (1), Br (2), I (3)), are reported. The ligand L is coordinated in a tetradentate coordination mode via two pyridyl-imine units, yielding the 12 π electron chelate ring. Herein, we indicated that using the pyridine based bulky ligand along with CdHal 2 salts led to formation of desirable helical metallo-organic molecules with octahedral geometry. It was found that all the structures exhibit intermolecular π⋯π stacking and C H⋯π interactions. The Hirshfeld analysis indicated that the H⋯X (X = H, C and Hal) contacts are highly favoured in 1 – 3. The optical properties of 1 – 3 have been investigated by diffuse reflectance spectroscopy. Graphical abstract Three new coordination compounds fabricated from CdHal 2 (Hal = Cl, Br, I) and a helical organic ligand 1,2-diphenyl-1,2-bis((phenyl(pyridin-2-yl)methylene)hydrazono)ethane (L) in MeOH, namely [CdCl 2 L] (1), [CdBr 2 L] (2) and [CdI 2 L] (3). Hirshfeld surface analysis showed that the structures of 1 – 3 are highly dominated by H⋯X (X = H, C and Hal) contacts. In the diffuse reflectance spectra, 1 – 3 each exhibit bands up to about 500 nm. Image Highlights • Coordination compounds of Cd(II) and 1,2-diphenyl-1,2-bis((phenyl(pyridin-2-yl)methylene)hydrazono)ethane were synthesized. • Hirshfeld surface analysis exhibited highly dominated H⋯X (X = H, C and Hal) contacts in the structures. • The optical properties have been investigated by diffuse reflectance spectroscopy. [ABSTRACT FROM AUTHOR]

Dethiobiotin synthetase from Mycobacterium tuberculosis (MtDTBS) is a promising antituberculosis drug target. Small‐molecule inhibitors that target MtDTBS provide a route towards new therapeutics for the treatment of antibiotic‐resistant tuberculosis. Adenosine diphosphate (ADP) is an inhibitor of MtDTBS; however, structural studies into its mechanism of inhibition have been unsuccessful owing to competitive binding to the enzyme by crystallographic precipitants such as citrate and sulfate. Here, a crystallographic technique termed precipitant–ligand exchange has been developed to exchange protein‐bound precipitants with ligands of interest. Proof of concept for the exchange method was demonstrated using cytidine triphosphate (CTP), which adopted the same binding mechanism as that obtained with traditional crystal‐soaking techniques. Precipitant–ligand exchange also yielded the previously intractable structure of MtDTBS in complex with ADP solved to 2.4 Å resolution. This result demonstrates the utility of precipitant–ligand exchange, which may be widely applicable to protein crystallography. [ABSTRACT FROM AUTHOR]

Investigations have been made on the photophysical behaviour of 8-hydroxy quinoline zinc metal chelate (Znq 2 ) under various environments such as temperature, humidity, UV radiation, acidic and basic solvents and polymer (PMMA: polymethylmetacrylate) matrix in order to explore the effect of these parameters on the photo luminescence (PL) spectra. Znq 2 is solvated in acetic acid and chloroform at different molar concentrations to calculate optical energy band gap as well as to study the shift of π → π* and the n → π* optical transitions in Zn 2+ ions and 8-hydroxy quinoline moieties. When the complex was subjected to annealing, the position of the emission peak remained unaltered at 504 nm with hypochromic shift at higher temperatures. The same has been observed when the complex is subjected to humid environment and UV exposure with no alteration in the emission peak in the former case and 1nm alteration in the later. The excitation and emission spectra of Znq 2 were recorded in basic and acidic solvents at different molar concentrations so as to establish a relation with the obtained absorption spectra. However, the emission peak blue shifted in basic media and red shifted in acidic media with variation in optical density. The PL spectra of molecular doped Znq 2 in PMMA blended films display an emission peak at 499 nm under excitation wavelength of 437 nm. CIE coordinates of Znq 2 were found to be close in all considered environments. These results prove that the emission from the synthesized metal complex can be tuned in the wavelength range of 433–524 nm by selecting the solvent or the polymer according to the requirement, inferring its potential as emissive material for the fabrication of organic light emitting diode (OLED), displays as well as in other optoelectronic applications where green light is essential. [ABSTRACT FROM AUTHOR]

A chiral ligand exchange capillary electrochromatography (CLE-CEC) protocol was designed and implemented for d , l -amino acids enantioseparation with poly(maleic anhydride-styrene-methacryloyl- l -arginine methyl ester) as the coating. The block copolymer was synthesized through the reversible addition fragmentation chain transfer reaction. In the constructed CLE-CEC system, poly (methacryloyl- l -arginine methyl ester) moiety of the block copolymer played the role as the immobilized chiral ligand and Zn (II) was used as the central ion. Key factors, including pH of buffer solution, ratio of Zn (II) to ligands, the mass ratio of monomers in the block copolymer, which affect the enantioresolution were investigated. Comparing with the bare capillary, the CLE-CEC enantioresolution was enhanced greatly with the coating one. 5 Pairs of d , l -amino acids enantiomers obtained baseline separation with 5 pairs partly separated. The mechanism of enhancement enantioresolution of the developed CLE-CEC system was explored briefly. Further, good linearities were achieved in the range of 25.0 μM–5.0 mM for quantitative analysis of d -glutamine (r 2  = 0.997) and l -glutamine (r 2  = 0.991). Moreover, the proposed CLE-CEC assay was successfully applied in the kinetics study of glutaminase by using l -glutamine as the substrate. [ABSTRACT FROM AUTHOR]

Abstract: This work deals with the enantioseparation of α‐amino acids by chiral ligand exchange high‐speed countercurrent chromatography using N‐n‐dodecyl‐ l‐hydroxyproline as a chiral ligand and copper(II) as a transition metal ion. A biphasic solvent system composed of n‐hexane/n‐butanol/aqueous phase with different volume ratios was selected for each α‐amino acid. The enantioseparation conditions were optimized by enantioselective liquid–liquid extractions, in which the main influence factors, including type of chiral ligand, concentration of chiral ligand and transition metal ion, separation temperature, and pH of the aqueous phase, were investigated for racemic phenylalanine. Altogether, we tried to enantioseparate 15 racemic α‐amino acids by the analytical countercurrent chromatography, of which only five of them could be successfully enantioseparated. Different elution sequence for phenylalanine enantiomer was observed compared with traditional liquid chromatography and the proposed interactions between chiral ligand, transition metal ion (Cu2+), and enantiomer are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Carnosine is present in high concentrations in specific human tissues such as the skeletal muscle, and among its biological functions, the remarkable scavenging activity toward reactive carbonyl species is noteworthy. Although the two enantiomers show almost identical scavenging reactivity toward reactive carbonyl species, only d‐carnosine is poorly adsorbed at the gastrointestinal level and is stable in human plasma. Direct methods for the enantioselective analysis of carnosine are still missing even though they could find more effective applications in the analysis of complex matrices. In the present study, the use of two different chiral stationary phases is presented. A chiral ligand‐exchange chromatography stationary phase based on N,S‐dioctyl ‐d‐penicillamine resulted in the direct enantioseparation of carnosine. Indeed, running the analysis at 25°C and 1.0 mL/min with a 1.5 mM copper(II) sulfate concentration allowed us to obtain separation and resolution factors of 3.37 and 12.34, respectively. However, the use of a copper(II)‐containing eluent renders it hardly compatible with mass spectrometry detectors. With the teicoplanin‐based stationary phase, a mass spectrometry compatible method was successfully developed. Indeed, a water/methanol 60:40 v/v pH 3.1 eluent flowed at 1.0 mL/min and with a 25°C column temperature produced separation and resolution factors of 2.60 and 4.16, respectively. [ABSTRACT FROM AUTHOR]

We herein developed a selective method for the determination of nucleotides by fluorous-assisted metal chelate affinity extraction followed by hydrophilic interaction liquid chromatography (HILIC) combined with tandem mass spectrometric (MS/MS) analysis. In this study, the nucleotides were selectively chelated by Fe(III)-immobilized perfluoroalkyliminodiacetic acid, and the resulting chelates were subsequently extracted into a fluorous solvent. The nucleotides present in the fluorous solvent were then back-extracted into a non-fluorous solution, such as a solution of ammonia in aqueous acetonitrile. The resulting non-fluorous solution containing the nucleotides was then directly injected into an amide-type HILIC column using a mixture of acetonitrile and aqueous ammonium bicarbonate as the mobile phase for gradient elution, and the nucleotides were detected using the negative electrospray ionization MS/MS mode. In this method, the extraction recoveries of the nucleotides ranged from 43.2 to 94.7% within a relative standard deviation of 17%. This method enabled the determination of intracellular concentrations of nucleotides. [ABSTRACT FROM AUTHOR]

Antigen-binding fragments (Fabs) of antibodies are both key biopharmaceuticals and valuable tools for basic life science. To streamline the production of diverse Fabs by capitalizing on standard and highly optimized protein production protocols, we here explore a method to prepare recombinant Fabs as secreted fusion proteins with an N-terminal human growth hormone domain and an octa-histidine tag. These tagged Fabs can be purified with standard immobilized metal chelate affinity chromatography. We first demonstrated Fab overproduction using the rat monoclonal antibody NZ-1. Optimization of linker residues enabled the complete removal of the tags by TEV protease, leaving only two additional residues at the N-terminus of the heavy chain. We purified NZ-1 Fab at ∼4 μg/mL of culture supernatant and further confirmed that the NZ-1 Fab from the fusion protein maintained its native fold and binding affinity for target cell-surface antigens. We also showed that several other Fabs of mouse IgG 1 s, the major subclass in mice, could be produced with the same procedure. Our preparation method can provide greater flexibility in functional and structural modifications of target Fabs because specialized purification techniques are not necessary. • A method was optimized for preparing Fabs as fusion proteins with human growth hormone (hGH) and octa-histidine tags. • hGH-fusion Fabs could be purified by standard immobilized metal chelate affinity chromatography. • Tag removal by TEV protease produced Fabs with only two additional residues at the N-terminus of the heavy chain. • NZ-1 Fab (rat IgG 2a , lambda) prepared as an hGH-fusion maintained its native fold and binding affinity for antigens. • Several mouse IgG 1 s were successfully prepared via the optimized method without protocol or construct modification. [ABSTRACT FROM AUTHOR]

Tailor-made materials for the purification of proteins with His-tag was designed through synergizing the selectivity of surface sieving and metal ion affinity. By excluding impurity proteins out of the surface polymer network, such materials could purify His-tagged proteins from the crude cell lysis with purity up to 90%, improved by 14% compared to that obtained by the commercial metal chelating affinity materials. This study might promote the His-tagged protein purification to a new level. [ABSTRACT FROM AUTHOR]

The accumulation of the extracellular β-amyloid (Aβ) aggregates with metal ions in conjunction with reactive oxygen species (ROS) is closely related to the pathogenesis of Alzheimer’s disease (AD). Accounting on Cu ions chelating of our previously designed bifunctional peptide GGHRYYAAFFARR (GR) as well as Aβ-Cu fibrils (fAβ-Cu) dissociation potentials, we report herein an efficient route to synthetically minimize ROS toxicity and degrade fAβ-Cu. It is worth mentioning that GR combines the metal chelating agent GGH and β-sheet breaker RYYAAFFARR (RR). The in vitro results have showed that GR disassociates fAβ-Cu into smaller fragments (sAβ-Cu, 150–200 nm), easily assimilated by PC12 cell and subsequently degraded in the lysosomes; GR can also suppress the ROS generated by fAβ-Cu. The viability of PC12 cell treated with fAβ-Cu has increased, from 38% to about 70% after administration of GR, overwhelming the GGH chelator (46%) and single functional peptide RR (48%). The in vivo results indicated that GR has efficiently reduced Aβ deposition, ameliorated neurologic changes and rescued memory loss, thus, enhancing the cognitive and spatial memory in a AD rat model. This study confirms the superior effect of GR and paves the way toward its future employment in large scale AD treatment. Statement of Significance We have focused on accelerating the degradation of fAβ-Cu as well as synthetically reducing the ROS toxicity by GR, and, consequently, its benefits in vivo . The bifunctional peptide GR can not only disaggregate fAβ-Cu into smaller fragments to facilitate uptake and degradation by PC12 cell, but also suppresses the ROS generated by fAβ-Cu. Thus, the viability of PC12 cell treated with fAβ-Cu has increased from 38% to 70% after GR administration, overwhelming GGH (46%) and RR (48%). The in vivo studies have revealed that GR improves the spatial memory ability and reduce the amount of senile plaques within brain of AD model rats. Thus, we suppose the bifunctional inhibitor GR has good application prospects in the treatment of AD treatment. [ABSTRACT FROM AUTHOR]

Radiofluorination of a 2.63 μM solution (pH 4, NaOAc buffer) of [AlCl3(BnMe2-tacn)] via treatment with 2.99 mol. equiv. of [19F]KF doped with cyclotron-produced [18F]F− target water, with heating to 80–100 °C for 1 h, gives up to 24% 18F incorporation. SPE purification of the [Al19F218F(BnMe2-tacn)] radio-product gives ＞99% RCP, with excellent stability (＞99% RCP after 3 h). [ABSTRACT FROM AUTHOR]

In this study, the qualitative and quantitative analysis of the absolute (100%) and aqueous (80%) methanolic extract of Carica papaya Linn processed seed flour samples in terms of their antioxidant properties and their phenolic compounds was investigated. The antioxidant properties were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power, and metal chelating assay methods. The protein isolate exhibited higher radical scavenging activity power as compared to other samples. Ferulic acid, caffeic acid, p-coumaric acid, kaempferol-3-glucoside, p-hydroxybenzoic acid, and quercetin-3-galactoside were phenolic compounds isolated with ferulic acid as high as 0.62 mg/DWg. Carica papaya seed isolates and concentrate demonstrated potent antioxidant activity and could be of nutraceutical importance in the pharmaceutical and food industry. [ABSTRACT FROM AUTHOR]

In search for new enantioselectivity profiles, the N -decyl- S -trityl-( R )-cysteine [C 10 -( R )-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for ligand-exchange chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0 mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C 10 -( R )-STC-based CSP, with resolution factor (R S ) values up to 8.86. Conformationally rigid and hydrophobic ligands often experienced the largest enantioselectivity effects. A high loadability emerged from the analysis of rac -NorVal (selected as prototype test compound): up to 20 mg/mL were efficiently enantioseparated with the CLEC-CSP. Two in-line hand-made cartridges filled with a strong cation-exchange resin allowed the effective catching of Cu(II) ions after the semi-preparative enantioseparation. The quantitative recovery of the rac -NorVal enantiomers was made possible by flowing through the cartridge a 5% (v) ammonia solution. The CLEC phase proved successful in the enantioselective analysis of a commercially available ( S )-Leu containing tablet. Furthermore, in order to understand the molecular basis for a successful use of the C 10 -( R )-STC-based CLEC system, a descriptive structure-separation relationship study was performed. As a result, all compounds with a MEAN-QPlogS (a hydrophilicity descriptor) value lower than 0.373 can be most likely enantioseparated with the CLEC system under investigation. In the work, the numerous aspects complying with the principles of green chromatography are highlighted and discussed. [ABSTRACT FROM AUTHOR]

Waste valorisation practices have attracted a significant amount of attention in recent years with the aim at managing waste in the most sustainable way. Most of the studies focused on converting solid waste feedstock for value-added chemicals and fuels production. However, less effort has been devoted on liquid waste such as beverage waste which is a significant sewage stream in urban area. In this study, a bioconversion process was developed to produce low-cost fructose syrup using beverages waste as feedstock. The process composed of enzymatic hydrolysis, activated carbon treatment, ion exchange chromatography and ligand exchange chromatography. Beverages waste collected from local supermarket was treated by commercial pectinase and sucrase. Optimisation study on enzyme activities indicated that both enzymes were most active at 50 °C and pH of 4.0-4.5. Hydrolysate containing 36.0 g/L glucose and 45.0 g/L fructose was then de-colourised in the activated carbon treatment. Also, more than 98% ions were removed after the cation and anion exchange chromatography. Lastly, high fructose syrup was produced by ligand exchange chromatography at a fructose separation efficiency of 74.9%. A total of 47.5% sugars in the hydrolysate were recovered as high fructose syrup, while the remaining sugars were in the glucose-rich stream. The proposed method would be a green and sustainable process for nutrient recovery in beverage waste valorisation. Future study should focus on increasing fructose separation efficiency by using simulated moving bed system and the enhancement of fructose production yield by isomerisation of glucose-rich stream. [ABSTRACT FROM AUTHOR]

Leishmania braziliensis and Leishmania infantum are the causative agents of cutaneous and visceral leishmaniasis, respectively. Several aspects of the vector-parasite interaction involving gp63 and phosphoglycans have been individually assayed in different studies. However, their role under the same experimental conditions was not studied yet. Here, the roles of divalent metal chelators, anti-gp63 antibodies and purified type I phosphoglycans (PGs) were evaluated during in vitro parasite attachment to the midgut of the vector. Parasites were treated with divalent metal chelators or anti-gp63 antibodies prior to the interaction with Lutzomyia longipalpis / Lutzomyia intermedia midguts or sand fly LL-5 cells. In vitro binding system was used to examine the role of PG and gp63 in parallel. Treatment with divalent metal chelators reduced Le. infantum adhesion to the Lu. longipalpis midguts. The most effective compound (Phen) inhibited the binding in both vectors. Similar results were observed in the interaction between both Leishmania species and the cell line LL-5. Finally, parallel experiments using anti-gp63-treated parasites and PG-incubated midguts demonstrated that both approaches substantially inhibited attachment in the natural parasite-vector pairs Le. infantum / Lu. longipalpis and Le. braziliensis / Lu. intermedia . Our results suggest that gp63 and/or PG are involved in parasite attachment to the midgut of these important vectors. [ABSTRACT FROM AUTHOR]

In the scope of a broader study focused on glutamate receptors regulators, we have been engaged in synthesis, analysis and pharmacological characterization of rigid analogues of glutamic acid. These compounds exhibited the bioisosteric replacement of the distal carboxylic group with the sulfonic one. Besides the sophisticated synthetic approach, we targeted preparation of a series of cyclopropyl-containing sulfonyl amino acids and development of a chromatographic enantioselective method suitable for distinguishing and quantifying the resulting isomers. Due to chelating ability, the chiral ligand-exchange chromatography (CLEC) was used for diastereo- and enantioseparation of the synthesized compounds. The CLEC-based enantioseparation was achieved by using a chiral mobile phase (CMP) system with N,N-dimethyl-( S)-phenylalanine [(S)-DMP] as the chiral selector. Only one of the investigated enantiomeric pairs was undiscriminated with the employed CLEC-CMP system which, very importantly, produced the simultaneous diastereo- and enantioseparation of two compounds of the series. Furthermore, the large α and RS values computed for three enantiomer pairs could be a good basis for a successful scale-up to a semi-preparative level. [ABSTRACT FROM AUTHOR]

4,5-Bis(2-methyl-5-phenylthiophen-3-yl)-1,3-dithiol-2-one (L1o) was elaborately designed to afford dithienyl-dithiolene as a new photochromic ligand. We describe herein the preparation and characterization of unprecedented photochromic dithienyl-dithiolene complexes with cis-orientation of dithienylethene (DTE) stabilized by metal chelation instead of conventional cyclopentene. The treatment of L1o with sodium methoxide in methanol afforded a disodium salt of dithiolate dianion, which reacts with M(dppe)Cl2 (dppe = 1,2-bis(diphenylphosphino)ethane, M = Ni, Pd) to give neutral compounds M(dppe)(dithiolate) as established by X-ray crystallography. The reaction of L1o with NiCl2 in the presence of sodium methoxide allows the isolation of an anionic nickel(ii) bis(dithienyl-dithiolene) complex with photochemical inertness. In contrast, the corresponding reaction with ZnCl2 afforded a dianionic zinc(ii) complex chelated by two dianionic dithienyl-dithiolenes, which displays stepwise photocyclization upon irradiation with UV light at 312 nm as demonstrated experimentally and theoretically. Only when dithienyl-dithiolene behaves as a dicationic ligand instead of neutral or monoanionic species, it is possible to achieve reversible photochromism in the corresponding metal complexes. [ABSTRACT FROM AUTHOR]

In this work, we developed an advanced bifunctional catalyst with both catalytic center and hydrogen donor to catalyze the aquathermolysis of the super-heavy oil from Shengli oil field. For efficiently separating the organosulfurs, we employed the PdCl 2 /silica gel ligand exchange chromatography (LEC) to obtain the critical organosulfurs, including polycyclic aromatic heterocycles (PAH), polycyclic aromatic sulfur heterocycles (PASH) and polar sulfur compounds (PSC), before and after aquathermolysis. GC–MS characterizations of the separated organosulfurs show that the nonconjugated C S bonds of high molecular weight compounds were cleaved to reduce the viscosity, while the conjugated C S bonds were stable under the catalytic aquathermolysis condition. Our work may provide a valuable insight on the conversion of organosulfurs in super-heavy oil for developing more efficient catalysts for aquathermolysis. [ABSTRACT FROM AUTHOR]

Silica gel containing silver ions was prepared and characterized. Silica was organofunctionalized with 3-mercaptopropyl group by using grafting reaction followed by silver ions adsorption (silver covalently bonded to mercaptopropyl silca gel, Ag-MPSG). The organofunctionalization and silver coordination were observed by transmission infrared spectroscopy and elemental analyses (CHN and EDS). The textural characteristics were studied by N 2 adsorption-desorption isotherms. Additionally, optical properties were studied by diffuse reflectance spectroscopy. The Ag-MPSG material was employed as stationary phase for the first time for fractionation of a heavy gas oil sample resulting in a fraction that is richer in polycyclic aromatic sulfur heterocycles (PASH). The fractions were analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detector and Ag-MPSG material provided similar fractionation performance when compared to conventional material [palladium covalently bonded to mercaptopropyl silca gel, Pd(II)-MPSG] usually employed for the same purpose and as the cost of silver is less than the one of palladium, the cost of the fractionation phase was reduced. [ABSTRACT FROM AUTHOR]

Nitrophenols are common pollutants detected in industrial effluents because they are used as basic raw materials in various industrial processes. Due to their toxicity to living things they are chemical species that need to be constantly monitored. Hence, the separation of nitrophenol isomers is very important to determine their levels in the environment. Since technical p-nitrophenol is contaminated with m-nitrophenol and the other aromatic compounds, the selective separation of p-nitrophenol from undesired impurities has become one of the important issues of the paracetamol synthesis. In the present work, a new chromatographic method for the separation of nitrophenol isomers on Co(II)-tris(carboxymethyl)ethylenediamine-silica gel (Co-CMEDA-Silica gel) has been developed using high performance liquid chromatography (HPLC). The chromatographic conditions were optimized by studying the effects of mobile phase composition. The positional isomers of nitrophenol ( o-, m-, and p-nitrophenol) could be separated by using ternary mobile phases with water/methanol/acetonitrile in the ratio 5:20:75 under isocratic conditions. The baseline separation of nitrophenol isomers has been achieved successfully with the stepwise gradient elution. [ABSTRACT FROM AUTHOR]

We have developed a fluorous affinity-based extraction method for measurement of protein kinase activity. In this method, a fluorescent peptide substrate was phosphorylated by a protein kinase, and the obtained phosphopeptide was selectively captured with Fe(III)-immobilized perfluoroalkyliminodiacetic acid reagent via a metal chelate affinity technique. Next, the captured phosphopeptide was selectively extracted into a fluorous solvent mixture, tetradecafluorohexane and 1 H ,1 H ,2 H ,2 H -tridecafluoro-1- n -octanol (3:1, v/v), using the specificity of fluorous affinity (fluorophilicity). In contrast, the remained substrate peptide in the aqueous (non-fluorous) phase was easily measured fluorimetrically. Finally, the enzyme activity could be assayed by measuring the decrease in fluorescence. The feasibility of this method was demonstrated by applying the method for measurement of the activity of cAMP-dependent protein kinase (PKA) using its substrate peptide (kemptide) pre-labeled with carboxytetramethylrhodamine (TAMRA). [ABSTRACT FROM AUTHOR]

The article explores on the enantioselective separation of chiral compounds on liquid chromatographic chiral stationary phases (CSPs) for the assessment of enantiomeric composition in chiral compounds. It examines the immobilization of chiral compounds in preparing ligand exchange CSPs. It also cites the reduction of gastric acid secretion in the ligand exchange of CSP.

A biphasic chiral recognition system based on chiral ligand exchange with Cu(II)- N- n-dodecyl-L-proline and hydroxypropyl-β-cyclodextrin as an additive was developed to enantioseparate aromatic β-amino acids by high-speed counter-current chromatography. The biphasic chiral recognition system was established with an n-butanol/water (1:1, v/v) solvent system by adding N- n-dodecyl-L-proline and Cu(II) ions to the organic phase and hydroxypropyl-β-cyclodextrin to the aqueous phase. Several separation parameters, such as temperature, pH value, and chiral selector concentration, were systematically investigated by enantioselective liquid-liquid extraction. Under the optimal separation conditions, 54.5 mg of ( R, S)-β-phenylalanine and 74.3 mg of ( R, S)-β-3,4-dimethoxyphenylalanine were baseline enantioseparated. More importantly, the synergistic enantiorecognition mechanism, based on the Cu(II)- N- n-dodecyl-L-proline and hydroxypropyl-β-cyclodextrin, was discussed for the first time. [ABSTRACT FROM AUTHOR]

The equilibrium model in enantioseparation of mandelic acid by chiral ligand exchange countercurrent chromatography was investigated using N -n-dodecyl- l -proline as chiral ligand and cupric ion as central metal. Important parameters, including physical partition coefficient and formation constants of binary and ternary coordination complexes in the two-phase solvent system, were determined. This equilibrium model could give an excellent prediction of distribution ratio and enantioseparation factor of the analyte in the biphasic solvent system, which was further verified by experiments. All the average relative deviations were less than 12%, indicating that the established model could provide a simple computational approach for optimization of enantioseparation conditions in chiral ligand exchange countercurrent chromatography. [ABSTRACT FROM AUTHOR]

In this study, we reported iminodiacetic acid–copper ion complex (IDA–Cu) immobilized onto gold nanoparticles (GNPs)-modified glassy carbon electrode as a novel electrochemical platform for selective and sensitive determination of lysozyme (Lys). IDA–Cu complex acted as an efficient recognition element capable of capturing Lys molecules. GNPs acts as a substrate to immobilize IDA–Cu coordinative complex and its interaction with Lys leds to a great signal amplification through measuring changes in differential pulse voltammetric (DPV) peak current of [Fe(CN) 6 ] 3−/4− redox probe. Upon the recognition of the Lys to the IDA–Cu, the peak current decreased due to the hindered electron transfer reaction on the electrode surface. Under optimum condition, it was found that the proposed method could detect Lys at wide linear concentration range (0.1 pM to 0.10 mM) with detection limit of 60 fM. Furthermore, electrochemical impedance spectroscopy (EIS) detection of Lys was demonstrated as a simple and rapid alternative analytical technique with detection limit of 80 fM at concentration range up to 0.1 mM. In addition, the proposed sensor was satisfactorily applied to the determination of Lys in real samples such as hen egg white. The proposed modified electrode showing the high selectivity, good sensitivity and stability toward Lys detection may hold a great promise in developing other electrochemical sensors based on metal–chelate affinity complexes. [ABSTRACT FROM AUTHOR]

The recombinant E7 oncoprotein gene of type 16 human papilloma virus (conjugated with the heat shock protein 70 (E7(16)-HSP70)) was expressed in Saccharomyces cerevisiae yeast cells. A number of chromatographic isolations were conducted to obtain the target protein and its primary identification and to establish its originality. The use of metal chelate chromatography was based on selective binding of sorbent active groups with a poly-histidine fragment at C-terminus of the target protein polypeptide sequence, while the use of affine chromatography was based on the association with ATP-binding regions of E7 and HSP70. The degree of purity of the target protein after both procedures did not exceed 70%, indicating the presence of many low-molecular admixtures and products of the target molecule oligomerization. The use of chromatographic purification under denaturing conditions using strong reducing agents allowed isolation of the target protein, the monomer content in which exceeded 97%. The target protein originality was established by immunoblotting and electrophoresis; the correspondence of its primary structure to the declared sequence was demonstrated by mass-spectrophotometry. [ABSTRACT FROM AUTHOR]

A chiral ligand-exchange high-performance method was developed for the enantioseparation of ofloxacin and its six related substances termed impurities A, B, C, D, E, and F. The separation was performed on a conventional C18 column. Different organic modifiers, copper salts, , the ratio of Cu2+ to amino acid, pH of aqueous phase, and column temperature were optimized. The optimal mobile phase conditions were methanol-water systems consisting of 5 mmol/L copper sulfate and 10 mmol/L L-isoleucine (L-Ile). Under such conditions, good enantioseparation of ofloxacin and impurities A, C, E, and F could be observed with resolutions ( RS) of 3.54, 1.97, 3.21, 3.50, and 2.12, respectively. On the relationship between the thermodynamic parameters and structures of analytes, the mechanism of was investigated. It was concluded that ofloxacin and impurities A, C, E, and F were all enthalpically driven enantioseparation and that low column temperature was beneficial to enantioseparation. Furthermore, the structure-separation relationship of these analytes is also discussed. Chirality 27:843-849, 2015. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A small molecular metal-chelate complex, tris(8-hydroxyquinoline-5-sulfonic acid) aluminum (AlQSA3), that has three sulfonic acid groups per molecule leading to an excellent solubility in water is reported as a liquid-free perfect solid-state electrolyte for flexible film-type all-solid-state energy storage devices. The AlQSA3 material is synthesized by one-step reaction of aluminum triisopropoxide and 8-hydroxyquinoline-5-sulfonic acid. The aqueous solutions of AlQSA3 are applied to fabricate flexible film-type all-solid state electric double layer capacitors with indium-tin oxide thin film electrodes. The ion conductivity of the AlQSA3 film reaches 0.116 mS cm−1, while a pronounced hysteresis are obtained in the cyclic voltammetry measurement. The AlQSA3 film capacitors exhibit an output voltage of 1.5 V at 20 μA cm−2, which is considerably stable by the repeated operation. In particular, the peak output voltage is well kept even after 180° bending for 500 times in the case of the flexible AlQSA3 film capacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ligand exchange HPLC (Pb2+) allows for separation of apiose from other sugars. • Post-column derivatization with fluorescence detection ensures high sensitivity assay. • Two-stage sulfuric acid hydrolysis was optimized for plant biomass sample preparation. • The developed method was tested on plant materials and apiose-containing pectins. Apiose is an unusual branched-chain pentose monosaccharide which does not occur naturally in a free form and included in the structure of some pectins and apioglycosides possessing high biological activity and having significant potential for use in pharmacology and cosmetic industry. The control of the chemical composition of plant raw materials and related products requires reliable analytical methods for determining apiose. In the present study a ligand exchange chromatography on a stationary phase bearing lead cations in combination with post-column derivatization by L-arginine and fluorescence detection was proposed for the highly sensitive and selective quantification of apiose. The optimized sample preparation procedure involves microscale two-stage hydrolysis with 72% and 0.5 M sulfuric acid at 30 °C and 100 °C, respectively. The developed and validated simple, robust and low-cost analytical method ensures limit of detection of 15 μg L–1 in liquid samples and 5 μg g−1 in plant material with a linear range comprising up to four orders of magnitude. It was successfully tested in the analyses of pharmaceutical preparations of the eelgrass pectins, parsley and fireweed biomass. [ABSTRACT FROM AUTHOR]

Two macrotricyclic ligands composed of two face-to-face octadentate metal chelates were synthesized. These cage-shaped disodium complexes had special recognition ability for various counter anions. Specific chiral dicarboxylates bound to the complexes within the cavity and exhibited chirality induction properties. For instance, N-Boc-Asp dianion strongly induced circular dichroism (CD) signals, but N-Boc-Glu dianion, which is one carbon longer, did not. [ABSTRACT FROM AUTHOR]

Mass cytometry (MC) offers unparalleled potential for the development of highly parameterized assays for characterization of single cells within heterogeneous populations. Current reagents compatible with MC analysis employ antibody-metal-chelating polymer conjugates to report on the presence of biomarkers. Here, we expand the utility of MC by developing the first activity-based probe designed specifically for use with the technology. A compact MC-detectable telluroether is linked to a bioreductively sensitive 2-nitroimidazole scaffold, thereby generating a probe sensitive to cellular hypoxia. The probe exhibits low toxicity and is able to selectively label O2-deprived cells. A proof-of-concept experiment employing metal-bound DNA intercalators demonstrates that a heterogeneous mixture of cells with differential exposure to O2 can be effectively discriminated by the quantity of tellurium-labeling. The organotellurium reagents described herein provide a general approach to the development of a large toolkit of MC-compatible probes for activity-based profiling of single cells. [ABSTRACT FROM AUTHOR]

This review highlights recent progresses in the chiral recognition and separation of amino acid enantiomers obtained by capillary electromigration techniques, using different chiral selectors and especially cyclodextrins, covering the literature published from January 2010 to March 2014. Sections are dedicated to the use of derivatization reagents and to the possibility to enantioseparate underivatized amino acids by using either ligand exchange capillary electrophoresis (LECE) and capillary electrophoresis (CE) coupled on line with mass spectrometry. A short insight on frontier nanomaterials is also given. [ABSTRACT FROM AUTHOR]

This work concentrates on the separation mechanism and application of chiral ligand exchange high-speed countercurrent chromatography in enantioseparation of ten racemic aromatic α-hydroxyl acids, including mandelic acid, 2-chloromandelic acid, 4-methoxymandelic acid, 4-hydroxymandelic acid, α-methylmandelic acid, 4-hydroxy-3-methoxy-mandelic acid, 3-chloromandelic acid, 4-bromomandelic acid, α-cyclopentylmandelic acid and α-cyclohexylmandelic acid, in which five of the racemates were successfully enantioseparated by analytical apparatus with an optimized solvent system. The two-phase solvent system was composed of butanol-water (1:1, v/v) or hexane- n -butanol-water (0.5:0.5:1, v/v), to which N- n -dodecyl- l -proline was added in the organic phase as chiral ligand and cupric acetate was added in the aqueous phase as a transition metal ion. Various influence factors in high-speed countercurrent chromatography were optimized by enantioselective liquid–liquid extraction. The separation mechanism for chiral ligand exchange high-speed countercurrent chromatography was proposed based on the results of present studies. Successful enantioseparations of 72 mg of mandelic acid, 76 mg of 2-chloromandelic acid and 74 mg of 4-methoxymandelic acid were achieved individually with high resolution by preparative high-speed countercurrent chromatography. The HPLC purity of all enantiomers was over 96% with the recovery in the range of 82–90% from the collected fractions. [ABSTRACT FROM AUTHOR]

This work reports that Cu(II) complexes with l-proline were used as chiral additives for the enantioseparations and determination of three underivatized amino acids by ligand-exchange micellar electrokinetic chromatography (LE-MEKC). Sodium dodecylsulfate (SDS) was shown to be necessary for simultaneous separation of the enantiomeric amino acids. Separation parameters such as SDS concentrations, the Cu(II)-l-proline ratio, the concentration of the copper(II) complex at a specific Cu(II)-l-proline ratio, pH and separation voltage were investigated for the enantioseparation in order to achieve the maximum possible resolution. A good separation was achieved in the BGE composing of 10mM ammonium acetate, 10mM Cu(II) and 20mM l-proline and 30mM SDS at pH 5.0, and an applied voltage of 15kV performed. Under above-mentioned optimum conditions, linearity was achieved within concentration ranges of up to two orders of magnitudes for the investigated amino acids with the correlation coefficients ranging from 0.9917 to 0.9984. The proposed method has been successfully applied to the determination of amino acid enantiomers in human urine, compound amino acids injection, and amino acid oral liquid. [ABSTRACT FROM AUTHOR]

A new approach, combining metal coordination with the molecular imprinting technique, was developed to prepare affinity materials. Magnetic poly(glycidyl methacrylate) microspheres in monosize form were used for specific recognition toward the target protein. The magnetic poly(glycidyl methacrylate) microspheres were prepared by dispersion polymerization in the presence of magnetite nanopowder. Surface imprinted magnetic poly(glycidyl methacrylate) microspheres based on metal coordination were prepared and used for the selective recognition of human serum albumin. Iminodiacetic acid was used as the metal coordinating agent and human serum albumin was anchored by Cu2+ ions on the surface of magnetic poly(glycidyl methacrylate) microspheres by metal coordination. The magnetic poly(glycidyl methacrylate) microspheres were coated with a polymer formed by condensation of tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane. The human serum albumin imprinted magnetic poly(glycidyl methacrylate) microspheres were characterized by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy and particle size analysis. The maximum adsorption capacity of human serum albumin imprinted magnetic poly(glycidyl methacrylate) microspheres was 37.7 mg/g polymer at pH 6.0. The selectivity experiments of human serum albumin imprinted magnetic poly(glycidyl methacrylate) microspheres prepared with different concentrations in the presence of lysozyme, bovine serum albumin and cytochrome C were performed in order to determine the relative selectivity coefficients. [ABSTRACT FROM AUTHOR]