Immobilized Ni Research Articles

The immobilized Ni(II) species on thiourea functionalized copper ferrite: a reusable nanocatalyst for synthesis of biscoumarins under solvent-free conditions

In this study, nanoparticles of CuFe2O4@SiO2@PTMS@Tu@Ni(II) as the reusable magnetic catalyst were prepared. Synthesis of the Ni(II)–CuFe2O4 system was carried out through a five-step procedure including the preparation of CuFe2O4 as the prime magnetic core, layering of silica, 3-chloropropyltrimethoxysilane and thiourea and finally the immobilization of Ni(OAc)2·4H2O. The prepared nanocomposite system was then characterized using FT-IR, SEM, EDX, XRD, VSM, ICP-OES and TGA/DSC analyses. Catalytic activity of CuFe2O4@SiO2@PTMS@Tu@Ni(II) was further studied toward synthesis of biscoumarin materials by a domino Knoevenagel–Michael reaction of 4-hydroxycoumarin with aromatic and heterocyclic aldehydes under solvent-free conditions (70 °C) within 15–30 min. The applied nanocomposite system was easily and magnetically separated from the reaction mixture and reused for six consecutive cycles without the significant loss of its catalytic activity.

The immobilized Ni(II)‐thiourea complex on silica‐layered copper ferrite: A novel and reusable nanocatalyst for one‐pot reductive‐acetylation of nitroarenes

In this study, magnetically nanoparticles of CuFe2O4@SiO2@PTMS@Tu@Ni(II) as novel and reusable catalyst were prepared. Synthesis of the Ni (II)‐nanocatalyst was carried out through the complexation of Ni(OAc)2·4H2O with the immobilized thiourea on silica‐layered CuFe2O4. The prepared nanocomposite system was then characterized using SEM, EDX, XRD, VSM, ICP‐OES, Raman, UV–Vis and FT‐IR analyses. Catalytic activity of the Ni(II)‐CuFe2O4 system was investigated towards rapid reduction of aromatic nitro compounds to arylamines with sodium borohydride as well as one‐pot reductive‐acetylation of nitroarenes to acetanilides with NaBH4/Ac2O system without the isolation of intermediate arylamines. All reactions were carried out in H2O within 3–7 min to afford the products arylamines/acetanilides in high to excellent yields. Reusability of the Ni(II)‐nanocatalyst was examined for seven consecutive cycles without the significant loss of the catalytic activity.

Prediction of the isotherms of human IgG adsorption on Ni(II)-IDA-PEVA membrane using artificial neural networks

The use of artificial neural networks (ANNs) to predict the adsorption isotherms of human immunoglobulin G on immobilized Ni(II) affinity hollow fiber membranes was studied. Neural networks were trained using the Levenberg–Marquardt algorithm combined with Bayesian regularization technique and experimental data from different temperatures. The resulting neural network demonstrated to be able to interpolate the behavior of the maximum adsorption capacity and equilibrium concentration in the temperature range (4, 37 °C) with correlation coefficients higher than 0.96. Results demonstrated to be very similar to those achieved with traditionally Langmuir model adjustment. The advantage of interpolation ability of ANNs was also showed.

Design of a Dinuclear Nickel(II) Bioinspired Hydrolase to Bind Covalently to Silica Surfaces: Synthesis, Magnetism, and Reactivity Studies

Presented herein is the design of a dinuclear Ni(II) synthetic hydrolase [Ni(2)(HBPPAMFF)(μ-OAc)(2)(H(2)O)]BPh(4) (1) (H(2)BPPAMFF = 2-[(N-benzyl-N-2-pyridylmethylamine)]-4-methyl-6-[N-(2-pyridylmethyl)aminomethyl)])-4-methyl-6-formylphenol) to be covalently attached to silica surfaces, while maintaining its catalytic activity. An aldehyde-containing ligand (H(2)BPPAMFF) provides a reactive functional group that can serve as a cross-linking group to bind the complex to an organoalkoxysilane and later to the silica surfaces or directly to amino-modified surfaces. The dinuclear Ni(II) complex covalently attached to the silica surfaces was fully characterized by different techniques. The catalytic turnover number (k(cat)) of the immobilized Ni(II)Ni(II) catalyst in the hydrolysis of 2,4-bis(dinitrophenyl)phosphate is comparable to the homogeneous reaction; however, the catalyst interaction with the support enhanced the substrate to complex association constant, and consequently, the catalytic efficiency (E = k(cat)/K(M)) and the supported catalyst can be reused for subsequent diester hydrolysis reactions.

The Analysis of the Immobilization Mechanism of Ni(II) on <I>Bacillus cereus</I>

This work focused on the identification of biosorption mechanism of Ni(II) by living Bacillus cereus (B. cereus) based on batch experiments and a variety of microscopic equipments. The adsorption equilibrium reached rapidly in 2 h and the maximum nickel adsorption capability of B. cereus was 17.7 mg x g(-1) (dry weight). Atomic force microscopy (AFM) analysis showed that the bacterial surface roughness increased from 7.9 +/- 0.5 nm to 12.6 +/- 1.6 nm during this process. Scanning electron microscopy (SEM) observation confirmed that there was Ni(II) on the bacterial surface. However, transmission electron microscopy (TEM) thin section analysis coupled with energy dispersive X-ray spectroscopy (EDS) revealed that Ni(II) could also be found in the inner portions of the bacteria. Inductive coupled plasma emission spectrometer (ICP-OES) quantitative analysis elucidated that over 70% of the immobilized Ni(II) was binding on the surface of bacteria. X-ray diffraction (XRD) analysis showed that the Ni(II) collected by the bacteria was amorphous. Fourier transform infrared (FT-IR) analysis indicated that amides and carboxylation functional groups might be involved in the coordination of Ni(II).

Evaluation of Immobilized Metal-Ion Affinity Chromatography (IMAC) as a Technique for IgG1 Monoclonal Antibodies Purification: The Effect of Chelating Ligand and Support

Monoclonal antibodies (MAbs) have been used for therapies and some analytical procedures as highly purified molecules. Many techniques have been applied and studied, focusing on monoclonal antibodies purification. In this study, an immobilized metal affinity chromatography membrane was developed and evaluated for the purification of anti-TNP IgG(1) mouse MAbs from cell culture supernatant after precipitation with a 50% saturated ammonium sulfate solution. The chelating ligands iminodiacetic acid, carboxymethylated aspartic acid (CM-Asp), nitrilotriacetic acid, and tris (carboxymethyl) ethylenediamine in agarose gels with immobilized Ni(II) and Zn(II) ions were compared for the adsorption and desorption of MAbs. The most promising chelating ligand--CM-Asp--was then coupled to poly(ethylene vinyl alcohol) (PEVA) hollow fiber membranes. According to SDS-PAGE and ELISA analyses, a higher selectivity and a purification factor of 85.9 (fraction eluted at 500 mM Tris) were obtained for IgG(1) using PEVA-CM-Asp-Zn(II). The anti-TNP MAb could be eluted under mild pH conditions causing no loss of antigen binding capacity.

Separation of hexahistidine fusion proteins with immobilized metal ion affinity chromatographic (IMAC) sorbents derived from MN+‐tacn and its derivatives

The capabilities of a new class of immobilized (im) metal ion chelate complexes (IMCCs), derived from 1,4,7-triazacyclononane (tacn), bis(1,4,7-triazacyclononyl) ethane (dtne) and bis(1,4,7-triazacyclononyl)propane (dtnp) complexed with the borderline metal ions Cu(2+), Ni(2+), Zn(2+), Mn(2+), Co(2+), and Cr(3+), for the purification of proteins have been investigated. In particular, the binding behavior of a model protein, the C-terminal hexahistidine tagged recombinant fusion protein Schistosoma japonicum glutathione S-transferase-Saccharomyces cerevisiae mitochondrial ATP synthase delta-subunit (GST-deltaATPase-His(6)), with these new immobilized metal ion affinity chromatographic (IMAC) sorbents was compared to the properties of a conventional sorbent, derived from immobilized Ni(II)-nitrilotriacetic acid (im-Ni(2+)-NTA). Investigations using the recombinant GST-deltaATPase-His(6) and recombinant S. japonicum glutathione S-transferase (GST) lacking a hexahistidine tag have confirmed that the C-terminal tag hexahistidine residues were required for the binding process to occur with these IMAC systems. The results also confirm that recombinant fusion proteins such as GST-deltaATPase-His(6) can be isolated in high purity with these IMAC systems. Moreover, these new macrocyclic systems manifest different selectivity features as a function of pH or ionic strength when compared to the conventional, unconstrained iminodiacetic acid (IDA) or NTA chelating ligands, complexed with borderline metal ions such as Cu(2+) or Ni(2+), as IMAC systems.

Chelating polymer-based membranes. Preparation and use for metal ion scavenging and sorption of murine immunoglobulin G by immobilized Ni(II) ions

Copolymers of 2-(2-hydroxyethoxy)ethyl methacrylate and ethylene dimethacrylate in the form of homogeneous membrane sheets were modified by chelating groups of iminodiacetic acid (IDA) in a two step reaction. The obtained sorbents showed high chelating capacity for Ni(II), Cu(II) and Fe(III) ions (up to 1.3 mmol/g). The potential use of immobilized Ni(II)-IDA complexes for sorption of murine immunoglobulin G by the immobilized metal affinity (IMA) method was tested. The sorption behaviour was characterized by a Langmuir-Freundlich adsorption isotherm. It was shown that the chelating membranes could be used for the sorption of low amounts of protein.

Nitrilotriacetic Acid-Coated Magnetic Nanoparticles as Affinity Probes for Enrichment of Histidine-Tagged Proteins and Phosphorylated Peptides

We herein demonstrate superparamagnetic Fe3O4 nanoparticles coated with nitrilotriacetic acid derivative (NTA) that can bind with different immobilized metal ions are capable of probing diverse target species. Immobilized Ni(II) on the surfaces of the NTA-magnetic nanoparticles have the capability of selectively trapping histidine (His)-tagged proteins such as a mutated streptopain tagged with 6x His, i.e., C192S (MW approximately 42 kDa), from cell lysates. Enrichment was achieved by vigorously mixing the sample solution and the nanoparticles by pipetting in and out of a sample vial for only 30 s. After enrichment, the probe-target species could be readily isolated by magnetic separation. We also characterized the proteins enriched on the affinity probes using on-probe tryptic digestion under microwave irradiation for only 2 min, followed by matrix-assisted laser desorption/ionization mass spectrometry analysis. Using this enrichment and tryptic digestion, the target species can be rapidly enriched and characterized, reducing the time required for carrying out the complete analysis to less than 10 min. Furthermore, when either Zr(IV) or Ga (III) ions are immobilized on the surfaces of the NTA-magnetic nanoparticles, the nanoparticles have the capability of selectively enriching phosphorylated peptides from tryptic digests of alpha-, beta-caseins, and diluted milk. The detection limit for the tryptic digests of alpha- and beta-caseins is approximately 50 fmol.

Nickel(macrocycle) Complexes Immobilized within Montmorillonite and MCM-41 as Catalysts for Epoxidation of Olefins

In this study, we have investigated the role of immobilized Ni(II) complexes with macrocyclic ligands of 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane (L) and 1,8-dibenzyl-1,3,6,8,10,13-hexaazacyclotetradecane (L′) within montmorillonite and MCM-41 as catalysts for epoxidation of cyclohexene, cyclopentene, norbornene, styrene and α-methylstyrene with tert-butylhydroperoxide (TBHP). The yield of epoxide in a given period depends mainly on the reaction rate of the complex with TBHP which is greatly affected by the alkene structure, ligand type and solid support. No desorption was observed during the course of reaction. Some mechanistic points will be presented in this article.

Genetic construction, properties and application of a green fluorescent protein-tagged ciliary neurotrophic factor.

The in vitro and in vivo actions of ciliary neurotrophic factor (CNTF) suggest that endogenous CNTF plays a role in nervous system development and maintenance. CNTF produces most, possibly all, of its effects by binding to a protein referred to as CNTF receptor alpha (CNTFRalpha). Information on CNTFRalpha tissue expression and dynamics would be advanced by the availability of reagents suitable for studying the subcellular localization and trafficking of CNTFRalpha. This paper describes the genetic construction, synthesis, purification and properties of a chimeric protein in which a highly fluorescent form of the green fluorescent protein (GFP) has been fused to human CNTF. The fusion protein, termed GFP-CNTF, was expressed in Escherichia coli. Histidine tagging of GFP-CNTF permitted ready purification by means of immobilized Ni(II) chromatography. Under non-reducing conditions GFP-CNTF migrated on SDS-PAGE with an apparent molecular mass of 50 kDa, although under reducing conditions it behaved electrophoretically as a 67 kDa species. Despite these discrepancies, the molecular mass of GFP-CNTF determined by mass spectrometry (54755) agreed well with its deduced relative molecular mass of 54536. Importantly, the absorbance profile of the GFP chromophore in GFP-CNTF was not modified by the presence of the CNTF domain. Moreover, the fluorescence emission spectrum of GFP-CNTF overlapped that of GFP, showing neither a change in absorbance shift nor a difference in the fluorescence quantum yield. Circular dichroism spectroscopy confirmed that the CNTF and GFP domains of GFP-CNTF folded independently of each other. GFP-tagged CNTF was equipotent to human CNTF in supporting the survival of cultured embryonic chicken sensory and ciliary ganglion neurons. GFP-CNTF, but not GFP, bound to immobilized CNTFRalpha and was displaced by an excess of human CNTF. GFP-CNTF specifically labeled the Purkinje cell layer in cerebellar slices from adult rat. This report is the first to describe a GFP chimera with a neurotrophic factor as the fusion partner. GFP-CNTF should provide a valuable tool for elucidating the role of CNTFRalpha in nervous system function.

Generation of a Ni(II) binding site by introduction of a histidine cluster in the structure of human glutathione transferase A1-1.

Two mutant forms of human glutathione transferase (GST) A1-1 with affinity for metal ions were constructed by introduction of His residues by site-directed mutagenesis. A mutant, 2-His, contained the mutations Lys84Gln, Asp85His and Glu88His, and another, 5-His, contained the mutations Tyr79His, Asn80His, Lys84His, Asp85His and Glu88His. The mutant proteins were obtained in good yields (40-150 mg per 3 l culture) by heterologous expression in Escherichia coli. The mutant enzymes possessed novel binding affinities for Ni(II) and Zn(II) ions, as demonstrated by immobilized metal ion affinity chromatography. The mutant with two novel His residues (2-His mutant) did not bind as tightly to immobilized Ni(II) as did the mutant with five novel His residues (5-His mutant). When tested for affinity to immobilized Zn(II), only the 5-His mutant remained bound to the column. The affinity of the 5-His mutant for Ni(II) ions in solution was determined by binding experiments in an aqueous polymeric two-phase system. Analysis of the binding curve showed two binding sites per enzyme subunit and a dissociation constant of 6.7 +/- 1.6 mu M. The kinetic constants kcat, Km and kcat/Km for the reaction with glutathione and 1-chloro-2,4-dinitrobenzene were determined by steady-state kinetic analysis and the parameter values for the mutant forms were found to be indistinguishable from those obtained for the wild-type GST A1-1. The differences in surface charge in the mutant proteins as compared with the wild-type enzyme did not alter the pH dependence of kcat. The results provide an alternative method for purification of fully active recombinant GST A1-1 by the introduction of novel metal binding sites. The data also showed that two His residues are sufficient for Ni(II) binding.

Chelating peptide-immobilized metal ion affinity chromatography. A new concept in affinity chromatography for recombinant proteins.

We report our experimental results supporting the hypothesis that a specific metal-chelating peptide (CP) on the NH2 terminus of a protein can be used to purify that protein using immobilized metal ion affinity chromatography (IMAC). The potential utility of this approach resides with recombinant proteins since the nucleotide sequence that codes for the protein can be extended to include codons for the chelating peptide and thereby generate the gene for a chimeric CP-protein that can be cloned, expressed, and affinity-purified with immobilized metal ions. The chelating peptide purification handle could then be removed chemically or enzymatically after purification has been achieved to generate a protein with the natural amino acid sequence. The feasibility of using a chelating peptide as a purification handle has been demonstrated using a leuteinizing hormone-releasing hormone (LHRH) analog, 2-10 LHRH, which contains the previously identified chelating peptide, His-Trp, on the NH2 terminus. 2-10 LHRH had a high affinity for a Ni(II) IMAC column due to the NH2-terminal dipeptide sequence His-Trp, forming a coordination complex with Ni(II), whereas the controls, 3-10 LHRH and 4-10 LHRH, lacking the CP sequence, did not bind. Furthermore, 2-10 LHRH could be purified from a mixture of histidine-containing peptides on a Ni(II) IMAC column in one step. His-Trp proinsulin was used as a model of a recombinant CP-protein. The S-sulfonates of His-Trp-proinsulin and proinsulin were isolated from Escherichia coli engineered to overproduce these proteins as trpLE' fusion proteins. His-Trp-proinsulin(SSO3-)6 had a higher affinity for immobilized Ni(II) than proinsulin (SSO3-)6. Both proteins were eluted by decreasing the pH or by introducing a displacing ligand into the buffer. Ni(II) eluted from the column with much higher concentrations of displacing ligand than the proteins.

Carboxypeptidase a: a model for studying the interaction of proteins with immobilized metal ions

The behavior of holocarboxypeptidase A (CPD(Zn)) and apocarboxypeptidase A (CPD) upon passage through metal-chelated gels was studied CPD is not retained on metal-free, Zn(II)- and Co(II)-chelated gels, but CPD(Zn) and its metal-free form bind to a Cu(II)-iminodiacetate (IDA) bed. After removal of Zn ion CPD acquires the ability to bind to a Ni(II)-IDA gel. This binding strongly suggests a selective interaction of CPD with immobilized Ni(II) through a group(s) on the enzyme molecule, responsible for active site metal binding (most probably His 69 and/or His 196) CPD is reactivated upon chromatography on Zn(II) → Co(II) → Ni(II)-loaded columns; this is consistent with the literature data concerning restoration of proteolytic activity CPD by metal ions in aqueous solutions. Metals immobilized by tris(carboxymethyl)ethylenediamine (TED), as compared with those chelated with IDA, exhibit a lower affinity to both forms of carboxypeptidase. Passage of CPD(Zn) through the metal-free TED gel reduces its proteolytic activity to that characteristic of CPD (4% of the activity of CPD(Zn)), while passage of CPD through this gel causes almost complete disappearance of the proteolytic activity (0.04% of that of CPD(Zn)). Therefore, metal-free TED columns may be useful for efficient preparation of metal-free proteins.

Immobilized metal ion affinity adsorption and immobilized metal ion affinity chromatography of biomaterials. Serum protein affinities for gel-immobilized iron and nickel ions.

Immobilized metal ion affinity adsorption (IMA adsorption) is a collective term that is proposed to include all kinds of adsorptions whereby metal atoms or ions immobilized on a polymer cause or dominate the interaction at the sorption sites. IMA chromatography is one of the most powerful methods available to date for protein fractionation although this is not as yet widely recognized. This study deals with the theoretical aspects of IMA adsorption and its practical applications as exemplified by the various results reported here. The synthesis of iminodiacetate-substituted agarose (IDA-agarose) and tris(carboxymethyl)ethylenediamine-agarose (TED-agarose) is described. Many types of metal ions can easily be immobilized on these gel derivatives to form IMA adsorbents. We have not observed any damage to the proteins during the adsorption-desorption process. After performance of an experiment, the gels can easily be regenerated and can be loaded with the same or a different metal ion for an ensuing experiment. Specific adsorption is demonstrated for serum proteins on immobilized Ni(II) and Fe(III). Ligand-specific desorption (affinity elution) is also demonstrated by including in the buffer system certain solutes which are similar to or identical with some particular amino acids found in proteins. High concentrations of certain salts that affect the structure of water, such as Na2SO4, promote coordinate covalent bonding of proteins by a mechanism that is apparently similar to that found in hydrophobic interactions. Neutral detergents and aquoorganic solvents may be used. This opens up the possibility for the fractionation of membrane components. The IMA-adsorption method could also be expanded to other areas besides protein fractionation.