Zhilin Wang

Preparation and Recognition Properties of Bovine Hemoglobin Magnetic Molecularly Imprinted Polymers

A simple method for the preparation of core-shell micro/nanostructured magnetic molecularly imprinted polymers (MIPs) for protein recognition is described. Magnetic MIPs were synthesized by copolymering gamma-aminopropyltrimethoxysilane and tetraethyl orthosilicate at the surface of Fe(3)O(4) nanospheres, which were directly covalently bound with template molecule, bovine hemoglobin (BHb), through imine bond. Transmission electron microscopy and scanning electron microscopy images showed that the Fe(3)O(4) nanospheres with diameter about 50-150 nm were coated with the MIPs layer with average thickness about 10 nm, which enabled the magnetic MIPs to have a sensitive and fast magnetic response. The proximity between the thickness of MIPs layer and the spatial size of BHb indicated that the imprinted sites almost situated at the surface of magnetic MIPs, leading a rapid adsorption saturation within 1 h. And the adsorption amounts of magnetic MIPs toward BHb were estimated to be 10.52 mg/g at pH 6.5, which was 4.6 times higher than that of magnetic nonmolecularly imprinted polymers. Meanwhile, the result of selective test showed that the magnetic MIPs had an excellent recognition capacity to BHb compared to the other nontemplate proteins. Except for the spatial size complementary between BHb and the binding sites in magnetic MIPs, the electrostatic interaction also was proven to be an important factor for recognizing the imprinting molecule.

Magnetic molecularly imprinted polymer for aspirin recognition and controlled release

Core-shell structural magnetic molecularly imprinted polymers (magnetic MIPs) with combined properties of molecular recognition and controlled release were prepared and characterized. Magnetic MIPs were synthesized by the co-polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) around aspirin (ASP) at the surface of double-bond-functionalized Fe(3)O(4) nanoparticles in chloroform. The obtained spherical magnetic MIPs with diameters of about 500 nm had obvious superparamagnetism and could be separated quickly by an external magnetic field. Binding experiments were carried out to evaluate the properties of magnetic MIPs and magnetic non-molecularly imprinted polymers (magnetic NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity and selectivity to ASP. Moreover, release profiles and release rate of ASP from the ASP-loaded magnetic MIPs indicated that the magnetic MIPs also had potential applications in drug controlled release.

Molecularly imprinted polymers microsphere prepared by precipitation polymerization for hydroquinone recognition

A one-step precipitation polymerization synthesis was adopted for the preparation of molecularly imprinted polymers (MIPs) by using hydroquinone as a template molecule. The transmission electron microscopy (TEM) exhibited that the polymers were uniform spheres with the diameter of about 700 nm. The results of adsorption experiments showed that the microspherical imprinted polymers possessed fast adsorption dynamics. Compared to the structurally similar compounds, catechol and resorcinol, the MIPs exhibited a high recognizable capacity to hydroquinone. And the electrochemical sensor fabricated by modifying the prepared MIPs microsphere on the glassy carbon electrode surface was used to detect the hydroquinone concentration. The current response was proportional to the concentration of hydroquinone in the range of 2.0 x 10(-6) to 1.0 x 10(-4)mol/L with the detection limit of 1.0 x 10(-6)mol/L.

A potent antitumor Zn2+ tetraazamacrocycle complex targeting DNA: the fluorescent recognition, interaction and apoptosis studies

A Zn(2+) tetraazamacrocycle complex (2) bearing three naphthalene moieties has been prepared. Complex 2 recognizes, binds and causes damage to DNA, and shows considerable cytotoxicity against human cervical (HeLa), breast (MCF-7) and lung (NCI-H157) cancer cell lines with a different apoptotic pathway from that of cisplatin.

Single-Crystalline EuF3 Hollow Hexagonal Microdisks: Synthesis and Application as a Background-Free Matrix for MALDI-TOF-MS Analysis of Small Molecules and Polyethylene Glycols

Single-crystalline EuF(3) hexagonal microdisks with hollow interior were fabricated to serve as a background-free matrix for analysis of small molecules and polyethylene glycols (PEGs) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The long-lived excited state of europium ions can transfer energy to high-energy vibrations of organic molecules, which provides the potential technological application in MALDI-TOF-MS analysis of small molecules and PEGs. The efficiency of the hollow microdisks as a novel matrix of low molecular weight compounds was verified by analysis of small peptide, amino acid, organic compounds, and hydroxypropyl beta-cyclodextrin (HP-beta-CD). The advantage of this matrix in comparison with alpha-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) was demonstrated by MALDI-TOF-MS analysis of an amino acid mixture and a peptide mixture. This matrix is successfully used for analysis of PEGs (PEG 2000, PEG 4000, PEG 8000, PEG 15000, and PEG 30000), suggesting a potential for monitoring reactions and for synthetic polymer quality control. The upper limit of detectable mass range was approximately 35,000 Da (PEG 30000). It is believed that this work will not only offer a new technique for high-speed analysis of small molecules and PEGs but also open a new field for applications of rare earth fluorides.

An NBD-armed tetraaza macrocyclic lysosomal-targeted fluorescent probe for imaging copper(II) ions.

An NBD-armed tetraaza macrocyclic lysosomal-targeted fluorescent probe for detecting Cu(2+) was synthesized and used for fluorescence imaging in HeLa cells. The probe was specifically localized in lysosomes and successfully applied to visualize Cu(2+) as well as to monitor Cu(2+) level changes in the lysosomes of living cells.

Indirect Transformation of Coordination‐Polymer Particles into Magnetic Carbon‐Coated Mn3O4 (Mn3O4@C) Nanowires for Supercapacitor Electrodes with Good Cycling Performance

Carbon-coated Mn3O4 nanowires (Mn3O4@C NWs) have been synthesized by the reduction of well-shaped carbon-coated bixbyite networks and characterized by TEM, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical experiments. To assess the properties of 1D carbon-coated nanowires for their use in supercapacitors, cyclic voltammetry and galvanostatic charging-discharging measurements were performed. Mn3O4 @C NWs could be charged and discharged faster and had higher capacitance than bare Mn3O4 nanostructures and other commercial materials. The capacitance of the Mn3O4@C NWs was 92% retained after 3000 cycles at a charging rate of 5 Ag(-1). This improvement can be attributed to the carbon shells, which promote fast Faradaic charging and discharging of the interior Mn3O4 core and also act as barriers to protect the inner core. These Mn3O4@C NWs could be a promising candidate material for high-capacity, low-cost, and environmentally friendly electrodes for supercapacitors. In addition, the magnetic properties of the as-synthesized samples are also reported to investigate the influence of the carbon coating.

Structure-function roles of four cysteine residues in the human arsenic (+3 oxidation state) methyltransferase (hAS3MT) by site-directed mutagenesis.

Cysteine (Cys) residues are often crucial to the function and structure of proteins. Cys157 and Cys207 in recombinant mouse arsenic (+3 oxidation state) methyltransferase (AS3MT) are shown to be related to enzyme activity and considered to be the catalytic sites. The roles of some conserved Cys residues in the N-terminal region of the rat AS3MT also have been examined. However, little is known about the roles of the Cys residues in the middle region. The metabolism of inorganic arsenic in human is different from rat and mouse in some aspects though the AS3MT has a high degree of similarity in these species. In order to determine whether the Cys156 and Cys206 (corresponding to the catalytic sites, Cys157 and Cys207 in the mouse AS3MT) in the hAS3MT act as the catalytic sites and to study the roles of the Cys residues (Cys226 and Cys250) near the catalytic center in the middle region, we designed and prepared four mutants (C156S, C206S, C226S, and C250S) in which one Cys residue replaced by serine by PCR-based site-directed mutagenesis. The native form and cysteine/serine mutants were assayed for enzyme activity, free thiols, and the secondary structures by circular dichroism and Fourier transform infrared. Our data show that, besides C156S and C206S, C250S is another potential important site. C226S seems to have the same action as the wild-type hAS3MT with the consistent K(M) and V(max) values. Meanwhile, selenium can also inhibit the methylation of inorganic arsenic by C226S. All the mutants except C226S are calculated to have dramatic changes in the secondary structures. Cys250 might form an intramolecular disulfide bond with another Cys residue. These findings demonstrate that Cys residues at positions 156, 206, and 250 play important roles in the enzymatic function and structure of the hAS3MT.

Synthesis of amine-functionalized Fe3O4@C nanoparticles for lipase immobilization

Amine-functionalized Fe3O4@C nanoparticles have been successfully synthesized on a large scale via a solvothermal route. The morphology, structure and properties of the Fe3O4@C nanoparticles were investigated through different analytical tools. Due to the magnetic nature and the presence of amine-functionalized groups, the as-prepared Fe3O4@C nanoparticles were employed as magnetic carriers for lipase immobilization. Our results indicate that the lipase loading amount on the magnetic Fe3O4@C nanoparticles was about 115.6 mg of protein per g. The factors related to the catalytic activity of the immobilized lipase on the magnetic carriers were systematically investigated. Hydrolytic activity tests reveal that the immobilized lipase retains about 93% of the free enzyme activity. It should be mentioned that the thermal stability of the immobilized lipase was strikingly higher than that of the free lipase. Most importantly, the immobilized lipase retained more than 68% of its initial activities after 10 times reuse. It is hoped that the amine-functionalized Fe3O4@C nanoparticles may find an application in biotechnology and catalysis.

New insights into the mechanism of arsenite methylation with the recombinant human arsenic (+3) methyltransferase (hAS3MT)

The catalytic mechanism of the recombinant human arsenic (+3) methyltransferase (hAS3MT) was studied using kinetics, initial velocity and spectroscopy. The production and the distribution of methylated arsenicals changed with various concentrations of arsenite/S-adenosyl-L-methionine (SAM)/thiols, enzyme contents, and incubation times. These results suggest a sequential methylation of arsenite to monomethylated arsenicals (MMA) and dimethylated arsenicals (DMA). In addition, competition exists between the two reactions. hAS3MT showed the greatest activity at pH 8.5 with glutathione (GSH) as the reductant. This might indicate that a balance between the deprotonation and protonation of sulfhydryl groups is required. Initial velocity studies illuminate an ordered sequence for the binding of SAM and arsenite to the hAS3MT; while GSH should probably be placed either as the first reactant or as a reactant combining with the enzyme only after products have been released. The interactions between substrate/cofactors and the hAS3MT were first monitored by UV-visible and circular dichroism spectroscopy. It revealed that arsenite and SAM combined with the hAS3MT before reaction started; whereas, no interactions between GSH and the hAS3MT were detected. Integrating the results from kinetics, initial velocity and spectroscopy studies, an ordered mechanism are originally attained, with the SAM as the first reactant that adds to the hAS3MT and arsenite as the second one. Arsenite is successively methylated reductively, rather than a stepwise oxidative methylation. GSH should combine with the hAS3MT after the methylation to reduce the disulfide bond formed during the catalytic cycle in the hAS3MT to resume the active form of the enzyme.