This paper describes a new support that permits to efficient immobilization of L-asparaginase (L-ASNase). For this purpose, Fe3O4 magnetic nanoparticles were synthesized and coated by MCM-41. 3-chloropropyltrimethoxysilane (CPTMS) was used as a surface modifying agent for covalent immobilization of L-ASNase on the magnetic nanoparticles. The chemical structure; thermal, morphological, and magnetic properties; chemical composition; and zeta potential value of Fe3O4@MCM-41-Cl were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction patterns (XRD), and zeta-potential measurement. The immobilization efficiency onto Fe3O4@MCM-41-Cl was detected as 63%. The reusability, storage, pH, and thermal stabilities of the immobilized L-ASNase were investigated and compared to that of soluble one. The immobilized enzyme maintained 42.2% of its original activity after 18 cycles of reuse. Furthermore, it was more stable towards pH and temperature compared with soluble enzyme. The Michaelis–Menten kinetic properties of immobilized L-ASNase showed a lower Vmax and a similar Km compared to soluble L-ASNase. Immobilized enzyme had around 47 and 32.5% residual activity upon storage a period of 28 days at 4 and 25 °C, respectively. In conclusion, the Fe3O4@MCM-41-Cl@L-ASNase core–shell nanoparticles could successfully be used in industrial and medical applications.
Journal of Thermal Analysis and Calorimetry - The heat exchanger pipe diameter has a significant effect on the flow characteristics as well as on the initial investment, operation and overall cost.... 相似文献
In this work, a new polymer resin with a functional groups capable of holding trace metals has been synthesized. The structure of polymer resin has been examined by BET-N2 method analyzer, IR spectrometer, scanning electron microscope (SEM) and elemental microanalyser. The synthesized polymer resin was used for the simultaneous separation and preconcentration of the trace metals from various tea and herbal plants samples. After extraction process, flame atomic absorption spectrometry (FAAS) was used to determine the trace metals. The analytical parameters and solid phase extraction (SPE) performance such as pH, sample volume, flow rates of sample, flow rates of eluent, concentration, volume and type of eluent and effect of interference ions, were investigated. The limits of detection (DL) of the SPE procedure for trace metals, were calculated to be (3s) in the range of 0.9?4.0 μg L?1 (n = 21) and the factors of preconcentration (PF) were obtained at 200 for Cd, Co, Cu, Fe, Ni and Zn, and at 50 for Cr, Mn and Pb ions and the relative standard deviation (RSD) at ≤ 2% (n = 11). 相似文献
The protein environments surrounding the retinal tune electronic absorption maximum from 350 to 630 nm. Hybrid quantum mechanical/molecular mechanical (QM/MM) methods can be used in calculating excitation energies of retinal in its native protein environments and in studying the molecular basis of spectral tuning. We hereby review recent QM/MM results on the phototransduction of bovine rhodopsin, bacteriorhodopsin, sensory rhodopsin II, nonretinal photoactive yellow protein and their mutants. 相似文献
Five new metal complexes [Pd(LH)2] (1), [Pd(L)2Ru2(bpy)4](ClO4)2 (2), [Pd(L)2Ru2(phen)4](ClO4)2 (3), [Pd(L)2Ru2(dafo)4](ClO4)2 (4) and [Pd(L)2Ru2(dcbpy)4](ClO4)2 (5), (where, L = ligand, bpy = 2,2′-bipyridine, phen = 1,10-phenantroline, dafo = 4,5-diazafluoren-9-one and dcbpy = 3,3′-dicarboxy-2,2′-bipyridine) have been isolated and characterized by UV-VIS, FT-IR, 1H NMR, magnetic susceptibility measurements, elemental analysis, molar conductivity, X-ray powder techniques, thermal analyses and their morphology studied by SEM measurements. IR spectra show that the ligand acts in a tetradentate manner and coordinates N4 donor groups of LH2 to PdII ion. The disappereance of H-bonding (O−H···O) in the trinuclear RuII-PdII-RuII metal complexes, the RuII ion centered into the main oxime core by the coordination of the imino groups while the two RuII ions coordinate dianionic oxygen donors of the oxime groups and linked to the ligands of bpy, phen, dafo and dbpy. The X-powder results show that 1 metal complex is indicating crystalline nature, not amorphous nature. Whereas, the X-ray powder pattern of the ligand (LH2) with 2, 3,4 and 5 exhibited only broad humps, indicating its amorphous nature. The catalytic activity of three different complexes were tested in the Suzuki coupling reaction. The 1, 4 and 5 metal complexes catalyse Suzuki coupling reaction between phenylboronic acid and arylbromides affording biphenyls. Also, the thermal results shown that the most stable complex is 1 compound while the less stable is 4 compound. 相似文献
Three novel vic-dioxime ligands containing the 1,8-diamino-3,6-dioxaoctane group, N,N′-(1,8-diamino-3,6-dioxaoctane)-p-tolylglyoxime (L1SL1H4), N,N′-(1,8-diamino-3,6-dioxaoctane)-phenylglyoxime (L2SL2H4), and N,N′-(1,8-diamino-3,6-dioxaoctane)-glyoxime (L3SL3H4) have been prepared from 1,8-diamino-3,6-dioxaoctane with anti-p-tolylchloroglyoxime, anti-phenylchloroglyoxime or anti-monochloroglyoxime. Polynuclear complexes [M(LxSLx)]n or [M(LxSLx)(H2O)]n (x = 1, 2 and 3), where M = CuII, CoII, and NiII, have been obtained with 1:1 metal/ligand ratio. The CuII and NiII poly-metal complexes of these ligands are proposed to be square planar, while also the prepared CoII complexes are proposed to be octahedral with two water molecules as axial ligands. The detection of H-bonding in the [Ni(L1SL1)]n, [Ni(L2SL2)]n and [M(L3SL3)(H2O)]n metal complexes by FT i.r. spectra revealed the square planar or octahedral [MN4·H2O)]n coordination of poly-nuclear metal complexes. [MN4]n coordination of the [Ni(L1SL1)]n and [Ni(L2SL2)]n complexes were also determined by 1H-n.m.r. spectroscopy. The ligands and poly-metal complexes were characterized by elemental analyses, FT-i.r., u.v.-vis.,
1H and 13C-n.m.r. spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, and differential pulse voltammetric
(DPV) techniques. 相似文献