Changes of antioxidative enzymes and cell membrane osmosis in tomato colonized by arbuscular Mycorrhizae under NaCl stress

Salinity toxicity is a worldwide agricultural and eco-environmental problem. Many literatures show that arbuscular mycorrhizal fungi (AMF) can enhance salt tolerance of many plants and some physiological changes occurred in AM symbiosis under salt stress. However, the role of ROS-scavenging enzymes in AM tomato is still unknown in continuous salt stress. This study investigated the effect of Glomus mosseae on tomato growth, cell membrane osmosis and examined the antioxidants (superoxide-dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX; peroxidase, POD) responses in roots of mycorrhizal tomato and control under different NaCl stress for 40 days in potted culture. NaCl solution (0, 0.5 and 1%) was added to organic soil in the irrigation water after 45 days inoculated by AMF (Glomus mosseae). (1) AMF inoculation improved tomato growth under salt or saltless condition and reduced cell membrane osmosis, MDA (malonaldehyde) content in salinity. So the salt tolerance of tomato was enhanced by AMF; (2) SOD, APX and POD activity in roots of AM symbiosis were significantly higher than corresponding non-AM plants in salinity or saltless condition. However, CAT activity was transiently induced by AMF and then suppressed to a level similar with non-AM seedlings; (3) higher salinity (1% level) and long stress time suppressed the effect of AMF on SOD, APX, POD and CAT activity; (4) this research suggested that the enhanced salt tolerance in AM symbiosis was mainly related with the elevated SOD, POD and APX activity by AMF which degraded more reactive oxygen species and so alleviated the cell membrane damages under salt stress. Whereas, the elevated SOD, POD and APX activity due to AMF depended on salinity environment.     

Chromatographic Properties of a “Comb-like” Chiral Stationary Phase Prepared via Atom Transfer Radical Polymerization

A “comb-like” chiral stationary phase was developed using surface-initiated technique via atom transfer radical polymerization (ATRP). Chlorinated silica gel was produced as the ATRP initiator in a one-step reaction with thionyl chloride. This initiation method results in a hydrolytically stable initial Si–C bond for poly(glycidyl methacrylate) (pGMA) chains grafted on the surface of silica gel. β-Cyclodextrin (β-CD) was immobilized on the pGMA chains with ring opening reaction to prepare the chiral stationary phase. This “comb-like” chiral stationary phase with the different pGMA chain length was evaluated by enatioseparation of structurally diverse racemic compounds under reversed-phase high-performance liquid chromatography. The chromatographic results demonstrate the effective chiral separation ability of the new chiral stationary phase.

     

Charge order driven by Fermi-arc instability and its connection with pseudogap in cuprate superconductors

The recently discovered charge order is a generic feature of cuprate superconductors, however, its microscopic origin remains debated. Within the framework of the fermion-spin theory, the nature of charge order in the pseudogap phase and its evolution with doping are studied by taking into account the electron self-energy (then the pseudogap) effect. It is shown that the antinodal region of the electron Fermi surface is suppressed by the electron self-energy, and then the low-energy electron excitations occupy the disconnected Fermi arcs located around the nodal region. In particular, the charge order state is driven by the Fermi-arc instability, with a characteristic wave vector corresponding to the hot spots of the Fermi arcs rather than the antinodal nesting vector. Moreover, although the Fermi arc increases its length as a function of doping, the charge order wave vector reduces almost linearity with the increase of doping. The theory also indicates that the Fermi arc, charge order and pseudogap in cuprate superconductors are intimately related to each other, and all of them emanates from the electron self-energy due to the interaction between electrons by the exchange of spin excitations.     

Preparation of bi-layer-polymer coated silica using atom transfer radical polymerization and its application as restricted access phase for HPLC separation of hydrophobic molecules in biological fluids

A novel restricted access material was prepared by surface initiated atom transfer radical polymerization. The bi-layer-polymer structures were created on the surface of silica layer-by-layer. The inner layer was composed of poly(styrene-co-divinylbenzene), which was grafted first for binding small molecules based on hydrophobic and π-π interactions. The poly(styrene-co-divinylbenzene) bonded silica has good selectivity for aromatic hydrocarbons. It also has hydrophobicity and column efficiency similar to a C(18) bonded silica. The material has shown good ability of protein exclusion after grafting hydrophilic polymer on the external surface while its hydrophobicity and selectivity do not have obvious change. It demonstrated that the material is still qualified for hydrophobic extraction. In the study, the relations between the polymer structures and chromatographic properties of the materials were investigated. The synthetic conditions were optimized. The results have shown that the material prepared in the study has application potential in the HPLC analysis of hydrophobic molecules from biological samples by direct injection. It demonstrated that atom transfer radical polymerization can be used as a method in the preparation of restricted access material.     

Chromatographic Properties of a “Comb-like” Chiral Stationary Phase Prepared via Atom Transfer Radical Polymerization

A “comb-like” chiral stationary phase was developed using surface-initiated technique via atom transfer radical polymerization (ATRP). Chlorinated silica gel was produced as the ATRP initiator in a one-step reaction with thionyl chloride. This initiation method results in a hydrolytically stable initial Si–C bond for poly(glycidyl methacrylate) (pGMA) chains grafted on the surface of silica gel. β-Cyclodextrin (β-CD) was immobilized on the pGMA chains with ring opening reaction to prepare the chiral stationary phase. This “comb-like” chiral stationary phase with the different pGMA chain length was evaluated by enatioseparation of structurally diverse racemic compounds under reversed-phase high-performance liquid chromatography. The chromatographic results demonstrate the effective chiral separation ability of the new chiral stationary phase.     

The effect of drug position on the properties of paclitaxel-conjugated gold nanoparticles for liver tumor treatment

Structure-efficacy effect of small molecular drug attracts wide attentions,but it has always been ignored in nanomedicine research.To reveal the efficacy modulation of nanomedicine,we developed a new type of paclitaxel(PTX)-conjugated gold nanoparticles(PTX-co njugated GNPs) to investigate the influence of drug position in controlling their in vitro properties and in vivo performance.Two therapeutic ligands(TA-PEG-NH-N=PTX and TA-PTX=N-NH-PEG) were synthesized to conjugate PTX on the surface of GNPs at different positions,locating on the surface of gold conjugate and inserting between GNPs and polyethylene glycol(PEG,molecular weight 1000 Da),respectively.It was found that PEG-PTX@GNPs with PTX located between GNP and PEG exhibited higher aqueous solubility,biocompatibility,and stability.In addition,an acid sensitive hydrazone bond has been inserted between PTX and PEG in both ligands for drug release of PTX and PTX-PEG segment,respectively,at the tumor site.Further release of PTX from PTX-PEG segment is based on the esterase hydrolysis of an ester bond between PTX and PEG.This two-step drug release mechanism offers PEG-PTX@GNPs effective and sustained release behavior for desirable anticancer activity,enhanced therapeutic efficacy,and lower systematic toxicity in Hepsbearing animal models.     

Synthesis of a novel restricted access chiral stationary phase based on atom transfer radical polymerization and click chemistry for the analysis of chiral drugs in biological matrices

A novel chiral restricted access material was synthesized via a combination of atom transfer radical polymerization (ATRP) and click chemistry. Poly(2-methyl-3-butyn-2-ol methacrylate) (pMBMA) was grafted onto porous silica gel by a surface-initiated ATRP in order to synthesize an inner layer for β-cyclodextrin (β-CD) immobilization. The azide-modified β-CD was bound to pMBMA by click chemistry. The results demonstrate that click chemistry provides an effective route for the immobilization of β-CD for chiral discrimination. A second ATRP reaction was then used to graft external poly(glycidyl methacrylate) (pGMA) layer onto the silica gel. The external hydrophilic layer was subsequently created by hydrolysis of the epoxy groups of the pGMA. This bi-layer grafted material exhibited both enantioseparation and protein exclusion. It can be used for the efficient separation of chiral compounds in biological samples with direct injection into an HPLC system.     

Determination of sulfonamides in bovine milk with column-switching high performance liquid chromatography using surface imprinted silica with hydrophilic external layer as restricted access and selective extraction material

A novel restricted access-molecularly imprinted material (RA-MIP) with selectivity for sulfonamides was synthesized using initiator-transfer agent-terminator (iniferter) method, a "living"/controlled radical polymerization technique. The material was prepared by grafting two layers with different functions on the silica support. To perform a "grafting from" polymerization, iniferter was immobilized on the surface of silica. The internal sulfamethazine imprinted polymer and the external poly(glycidyl methacrylate) [poly(GMA)] were then grafted successively. The hydrophilic structures were formed on the external layer of the material by the hydrolysis of the linear poly(GMA) for protein removal. The result has shown that this restricted access-MIP grafted silica (RA-MIP-SG) not only has the selectivity for the template and its analog, but also has the ability of exclusion for bovine serum albumin (BSA). It indicated that the material possesses both properties of molecularly imprinted polymer (MIP) and restricted access material (RAM). Using RA-MIP-SG as pre-column, a column-switching HPLC method was established for the determination of sulfonamides in bovine milk. Direct sample injection was performed in the analysis, which provides a convenient analytical procedure. Good linearity in the range of 2-400 ng mL(-1) (R>0.998) has been obtained for seven sulfonamides in the study. The recoveries of all the analytes at three concentration levels are between 93% and 107% with the RSD<8.0%. The limits of quantification and limits of detection are less than or equal to 2.7 ng mL(-1) and 0.8 ng mL(-1) respectively. It demonstrated this RA-MIP-SG can be applied in sample extraction and clean-up for the determination of sulfonamides in bovine milk by direct injection and column-switching HPLC with good efficiency and reliability.