Synthesis of novel magnetic nano-sorbent functionalized with N-methyl-D-glucamine by click chemistry and removal of boron with magnetic separation method.

Click chemistry refers to a group of reactions that are fast, simple to use, easy to purify, versatile, regiospecific, and give high product yields. Therefore, a novel, efficient magnetic nano-sorbent based on N-methyl-D-glucamine attached to magnetic nanoparticles was prepared using click coupling method. Its boron sorption capacity was compared with N-methyl-D-glucamine direct attached nano-sorbent. The characterization of the magnetic sorbents was investigated by several techniques such as X-ray diffraction, scanning electron microscope, transmission electron microscope, dynamic light scattering, thermogravimetric analysis, Fourier transform infrared spectrophotometer, and vibrating sample magnetometer. The boron sorption capacity of sorbents was compared by studying various essential factors influencing the sorption, like sorbate concentration, sorbents dosage, pH of the solution, and contact time. Langmuir and Freundlich and Dubinin-Radushkevich adsorption isotherms models were applied. Percent removal and sorption capacities efficiencies of sorbents obtained with direct and click coupling are found to be 49.5%, 98.7% and 6.68 mg/g, 13.44 mg/g respectively. Both sorbents have been found to be compatible with Langmuir isotherm, and the boron sorption kinetics conforms to the pseudo second order kinetics. The reusability study of sorbents was carried out five times for boron sorption and desorption.

Enantioseparation of Mandelic Acid Enantiomers With Magnetic Nano-Sorbent Modified by a Chiral Selector.

In this study, R(+)-α-methylbenzylamine-modified magnetic chiral sorbent was synthesized and assessed as a new enantioselective solid phase sorbent for separation of mandelic acid enantiomers from aqueous solutions. The chemical structures and magnetic properties of the new sorbent were characterized by vibrating sample magnetometry, transmission electron microscopy, Fourier transform infrared spectroscopy, and dynamic light scattering. The effects of different variables such as the initial concentration of racemic mandelic acid, dosage of sorbent, and contact time upon sorption characteristics of mandelic acid enantiomers on magnetic chiral sorbent were investigated. The sorption of mandelic acid enantiomers followed a pseudo-second-order reaction and equilibrium experiments were well fitted to a Langmuir isotherm model. The maximum adsorption capacity of racemic mandelic acid on to the magnetic chiral sorbent was found to be 405 mg g(-1). The magnetic chiral sorbent has a greater affinity for (S)-(+)-mandelic acid compared to (R)-(-)-mandelic acid. The optimum resolution was achieved with 10 mL 30 mM of racemic mandelic acid and 110 mg of magnetic chiral sorbent. The best percent enantiomeric excess values (up to 64%) were obtained by use of a chiralpak AD-H column.

Heterofunctional Magnetic Metal-Chelate-Epoxy Supports for the Purification and Covalent Immobilization of Benzoylformate Decarboxylase From Pseudomonas Putida and Its Carboligation Reactivity.

In this study, the combined use of the selectivity of metal chelate affinity chromatography with the capacity of epoxy supports to immobilize poly-His-tagged recombinant benzoylformate decarboxylase from Pseudomonas putida (BFD, E.C. 4.1.1.7) via covalent attachment is shown. This was achieved by designing tailor-made magnetic chelate-epoxy supports. In order to selectively adsorb and then covalently immobilize the poly-His-tagged BFD, the epoxy groups (300 µmol epoxy groups/g support) and a very small density of Co(2+)-chelate groups (38 µmol Co(2+)/g support) was introduced onto magnetic supports. That is, it was possible to accomplish, in a simple manner, the purification and covalent immobilization of a histidine-tagged recombinant BFD. The magnetically responsive biocatalyst was tested to catalyze the carboligation reactions. The benzoin condensation reactions were performed with this simple and convenient heterogeneous biocatalyst and were comparable to that of a free-enzyme-catalyzed reaction. The enantiomeric excess (ee) of (R)-benzoin was obtained at 99 ± 2% for the free enzyme and 96 ± 3% for the immobilized enzyme. To test the stability of the covalently immobilized enzyme, the immobilized enzyme was reused in five reaction cycles for the formation of chiral 2-hydroxypropiophenone (2-HPP) from benzaldehyde and acetaldehyde, and it retained 96% of its original activity after five reaction cycles.

Kinetic approach for the purification of nucleotides with magnetic separation.

The isolation of ß-nicotinamide adenine dinucleotide is of great importance since it is widely used in different scientific and technologic fields such as biofuel cells, sensor technology, and hydrogen production. In order to isolate ß-nicotinamide adenine dinucleotide, first 3-aminophenyboronic acid functionalized magnetic nanoparticles were prepared to serve as a magnetic solid support and subsequently they were used for reversible adsorption/desorption of ß-nicotinamide adenine dinucleotide in a batch fashion. The loading capacity of the 3-aminophenyboronic acid functionalized nanoparticles for ß-nicotinamide adenine dinucleotide adsorption was 13.0 µmol/g. Adsorption kinetic and isotherm studies showed that the adsorption process followed a pseudo-second-order kinetic model and the experimental data can be represented using Langmuir isotherm model. The 3-aminophenyboronic acid functionalized magnetic nanoparticles were proposed as an alternative support for the ß-nicotinamide adenine dinucleotide purification. The results elucidated the significance of magnetic separation as a fast, relatively simple, and low-cost technique. Furthermore, the magnetic supports can be reused at least five times for purification processes.

Carboligation reactions mediated by benzoylformate decarboxylase immobilized on a magnetic solid support.

In this study, magnetic nanoparticles (Fe3 O4 , magnetite) with immobilized metal affinity ligands (MSS) were prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), and vibrating-sample magnetometer (VSM) methods for purification and immobilization of the histidine-tagged recombinant benzoylformate decarboxylase (BFD). The MSS support was shown to be eligible for selective binding of HIS-tagged BFD by SDS-page analysis. Loading capacity of the MSS support was determined as 43.6 ± 1.1 mg/g. The regeneration ability for protein binding was also studied. An immobilized BFD was tested to catalyze benzoin condensation and representative cross acyloin reaction. Conversion and enantiomeric excess values were comparable with that of free enzyme catalyzed reactions.

Carboligation reactions with benzaldehyde lyase immobilized on superparamagnetic solid support.

Histidine-tagged recombinant benzaldehyde lyase (BAL, EC 4.1.2.38) was efficiently immobilized to surface-modified magnetic particles with affinity ligand binding. In addition to conventional benzoin condensation reactions, two important representative BAL-catalyzed carboligation reactions, were also performed with this magnetically responsive biocatalyst. The results obtained from the carboligation reactions that were performed with this simple and convenient heterogenous biocatalyst were comparable to that of free-enzyme-catalyzed reactions.

Preparation and characterization of Ni-nitrilotriacetic acid bearing poly(methacrylic acid) coated superparamagnetic magnetite nanoparticles.

Stable superparamagnetic magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in the presence of poly(methacrylic acid) (PMAA) in aqueous solution. The polymer coated Fe3O4 nanoparticles were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thermal analysis, and vibrating sample magnetometry (VSM) techniques. These measurements reveal the presence of magnetite nanoparticles with a size of approximately 8 nm inside the PMAA matrix. The magnetization value of these superparamagnetic nanoparticles at room temperarure and 7 T was measured as about 40 emu/g. PMAA-coated Fe3O4 nanoparticles were further assembled with Ni-chelate through a reaction between a primary amine-bearing NTA (nitrilotriacetic acid) ligand and carboxy-functional groups of PMAA. NTA-PMAA-coated magnetite nanoparticles were then loaded with nickel ions and characterized using FTIR. The average amount of binded Ni on the surface of the NTA-modified PMAA coated Fe3O4 was calculated as 1.65 +/- 0.3 x 10(-6) mol nickel(II) ions per g of the magnetic particles from the inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements.

Rapid synthesis and characterization of maghemite nanoparticles.

Fe2O3-SiO2 nanocomposites were prepared by a sol-gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3-SiO2 sols were gelated at various temperatures ranging from 50 degrees C to 70 degrees C, and subsequently they were calcined in air at 400 degrees C for 4 hours. The structure and the magnetic properties of the prepared Fe203-SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3-SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 degrees C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10 K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 degrees C, respectively. At the gelation temperature of 70 degrees C, gamma-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9 +/- 2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.