Genome-Wide Identification and Expression Analysis of the Cucumber FKBP Gene Family in Response to Abiotic and Biotic Stresses.

The FKBP (FK506-binding protein) gene family is an important member of the PPlase protease family and plays a vital role during the processes of plant growth and development. However, no studies of the FKBP gene family have been reported in cucumber. In this study, 19 FKBP genes were identified in cucumber, which were located on chromosomes 1, 3, 4, 6, and 7. Phylogenetic analysis divided the cucumber FKBP genes into three subgroups. The FKBP genes in the same subgroup exhibited similar structures and conserved motifs. The cis-acting elements analysis revealed that the promoters of cucumber FKBP genes contained hormone-, stress-, and development-related cis-acting elements. Synteny analysis of the FKBP genes among cucumber, Arabidopsis, and rice showed that 12 kinds of syntenic relationships were detected between cucumber and Arabidopsis FKBP genes, and 3 kinds of syntenic relationships were observed between cucumber and rice FKBP genes. The tissue-specific expression analysis showed that some FKBP genes were expressed in all tissues, while others were only highly expressed in part of the 10 types of tissues. The expression profile analysis of cucumber FKBP genes under 13 types of stresses showed that the CsaV3_1G007080 gene was differentially expressed under abiotic stresses (high temperature, NaCl, silicon, and photoperiod) and biotic stresses (downy mildew, green mottle mosaic virus, Fusarium wilt, phytophthora capsica, angular leaf spot, and root-knot nematode), which indicated that the CsaV3_1G007080 gene plays an important role in the growth and development of cucumber. The interaction protein analysis showed that most of the proteins in the FKBP gene family interacted with each other. The results of this study will lay the foundation for further research on the molecular biological functions of the cucumber FKBP gene family.

Nanocomposites consisting of nanoporous platinum-silicon and graphene for electrochemical determination of bisphenol A.

Three-dimensional nanoporous PtSi (NP-PtSi) alloy was prepared by dealloying ternary PtSiAl alloy ribbons. By combining the nanoporous morphology of PtSi and graphene (GR), a new composite material was developed, which was used to modify the surface of a glassy carbon electrode (GCE). The resulting modified electrodes showed an excellent electrocatalytic activity towards the electro oxidation of bisphenol A. Based on differential pulse voltammetry measurements, NP-PtSi/GR/GCE showed linear response over the concentration range 0.30 to 85 µM bisphenol A, while the detection limit was found to be 0.11 µM (S/N = 3). NP-PtSi/GR/GCE showed also satisfactory stability and selectivity over various compounds present in real samples, and they were successfully applied to the determination of bisphenol A in inoculated milk samples. Graphical abstract Nanoporous PtSi (NP-PtSi) was fabricated by dealloying PtSiAl alloy ribbons. Based on the NP-PtSi alloy and graphene (GR) composites that modified glassy carbon electrode (GCE), a sensitive and stable electrochemical sensor was developed for the determination of bisphenol A by differential pulse voltammetric (DPV) method.

Electrochemical determination of dopamine using a glassy carbon electrode modified with a nanocomposite consisting of nanoporous platinum-yttrium and graphene.

A nanoporous platinum-yttrium alloy (NP-PtY) was fabricated by dealloying ribbons of a PtYAl alloy. Owing to the high porosity and the synergistic effect of Y in the Pt backbone, the NP-PtY exhibits superior structural stability, reproducibility and electrocatalytic activity. An electrochemical sensor was developed for the highly sensitive and selective detection of dopamine (DA) based on the use of a glassy carbon electrode modified with NP-PtY alloy and graphene. The sensor, best operated at 0.16 V vs. SCE, has a linear range covering the 0.9 to 82 µM concentration range, a 0.36 µM detection limit (at S/N = 3), and good selectivity over tyramine, tryptamine, phenethylamine, uric acid, and ascorbic acid. It gave satisfactory results in the determination of DA in spiked samples of urine. Graphical abstract Nanoporous platinum-yttrium alloy (NP-PtY) was fabricated by means of a one-step dealloying process. A glassy carbon electrode modified with the NP-PtY and graphene nanocomposite exhibits a wide linear range and a low detection limit towards dopamine. The sensor has remarkable reproducibility, stability and selectivity.

Facile Synthesis of Nanoporous Pt-Y alloy with Enhanced Electrocatalytic Activity and Durability.

Recently, Pt-Y alloy has displayed an excellent electrocatalytic activity for oxygen reduction reaction (ORR), and is regarded as a promising cathode catalyst for fuel cells. However, the bulk production of nanoscaled Pt-Y alloy with outstanding catalytic performance remains a great challenge. Here, we address the challenge through a simple dealloying method to synthesize nanoporous Pt-Y alloy (NP-PtY) with a typical ligament size of ~5 nm. By combining the intrinsic superior electrocatalytic activity of Pt-Y alloy with the special nanoporous structure, the NP-PtY bimetallic catalyst presents higher activity for ORR and ethanol oxidation reaction, and better electrocatalytic stability than the commercial Pt/C catalyst and nanoporous Pt alloy. The as-made NP-PtY holds great application potential as a promising electrocatalyst in proton exchange membrane fuel cells due to the advantages of facile preparation and excellent catalytic performance.

Phosphorus-doped helical carbon nanofibers as enhanced sensing platform for electrochemical detection of carbendazim.

A combined chemical vapor deposition with high-pressure annealing has been developed for the production of phosphorus-doped helical carbon nanofibers (P-HCNFs). The resulting P-HCNFs have a large specific surface area, well-defined three-dimensional hierarchical helical structure and rapid apparent heterogeneous electron transfer. Based on the high electrocatalytic activity, the P-HCNFs were used to develop an amperometric sensor for carbendazim detection. The experimental results demonstrated that the sensor is promising for the determination of carbendazim in food samples due to the high sensitivity, wide linear range and low detection limit.

Nanocomposite of Au Nanoparticles/Helical Carbon Nanofibers and Application in Hydrogen Peroxide Biosensor.

A combined sol-gel/hydrogen reduction method has been developed for the mass production of helical carbon nanofibers (HCNFs) by the pyrolysis of acetylene at 425 degrees C in the presence of NiO nanoparticles. The synthesized HCNFs were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The helical-structured carbon nanofibers have a large specific surface area and excellent biocompatibility. A novel enzymatic hydrogen peroxide sensor was then successfully fabricated based on the nanocomposites containing HCNFs and gold nanoparticles (AuNPs). The results indicated that the Au/HCNFs nanocomposites exhibited excellent electrocatalytic activity to the reduction of H2O2, offering a wide linear range from 1.0 µM to 3157 µM with a detection limit as low as 0.46 µM. The apparent Michaelis-Menten constant of the biosensor was 0.61 mM. The as-fabricated biosensor showed a rapid and sensitive amperometric response to hydrogen peroxide with acceptable preparation reproducibility and excellent stability. Because of their low cost and high stability, these novel HCNFs represent seem to be a kind of promising biomaterial and may find wide new applications in scopes such as biocatalysis, immunoassay, environmental monitoring and so on.

Real-time monitoring on the adsorption process of salicylic acid onto chitosan membrane using dielectric spectroscopy: macroscale concentration polarization and dynamics.

The adsorption process of salicylic acid (SA) onto chitosan membrane is monitored in real time by the dielectric relaxation spectroscopy (DRS) method. A unique dielectric relaxation, which is related to the macroscale concentration polarization layers (CPLs) in the SA solution caused by the adsorption, is observed. By modeling the measured systems composed of the membrane, the CPLs, and the SA solution, the dielectric spectra are analyzed systematically on the basis of the interfacial polarization theory. The parameters about the constituent phases, i.e., the dielectric constant εm and the conductivity κm of the chitosan membrane, the conductivity distribution (κ1 to κ2), and the thickness dCPL of the CPL, are obtained. The time-dependent εm and κm give insight into the microstate of the chitosan membrane during the adsorption. Furthermore, the time evolution of the conductivity gradient of the CPL, Δκ/dCPL, is combined to interpret the adsorption mechanism. It is suggested that the noninvasive dielectric monitoring may be applied to many adsorption and release processes.

A novel enzymatic hydrogen peroxide biosensor based on Ag/C nanocables.

A novel enzymatic hydrogen peroxide sensor was successfully fabricated based on the nanocomposites containing of Ag/C nanocables and gold nanoparticles (AuNPs). Ag/C nanocables have been synthesized by a hydrothermal method and then AuNPs were assembled on the surface of Ag/C nanocables. The nanocomposites were confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS). The above nanocomposites have satisfactory chemical stability and excellent biocompatibility. Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the Ag/C/Au nanocomposites at glassy carbon electrode (GCE). The results indicated that the Ag/C/Au nanocomposites exhibited excellent electrocatalytic activity to the reduction of H(2)O(2). It offered a linear range of 6.7×10(-9) to 8.0×10(-6) M, with a detection limit of 2.2×10(-9) M. The apparent Michaelis-Menten constant of the biosensor was 51.7×10(-6) M. These results indicated that Ag/C/Au nanocomposites have potential for constructing of a variety of electrochemical biosensors.

Direct electrochemistry and electrocatalytic behavior of hemoglobin entrapped in Ag@C nanocables/gold nanoparticles nanocomposites film.

Direct electrochemistry of hemoglobin (Hb) was successfully fabricated by immobilizing Hb on the nanocomposites containing of Ag@C nanocables and Au nanoparticles (AuNPs) modified glassy carbon electrode (GCE). The immobilized Hb retained its biological activity and shown high catalytic activities to the reduction of H2O2 by circular dicroism (CD) spectrum, fourier transform infrared (FT-IR) spectrum and cyclic voltammetry (CV). Experimental conditions such as scan rate and pH Value were studied and optimized. The results indicated that the resulting biosensor are linear to the concentrations of H2O2 in the ranges of 6.67 x 10(-7)-2.40 x 10(5) M, and the detection limit is 2.02 x 10(-7) M. The electrochemical biosensor has also high stability and good reproducibility.

Helical carbon nanotubes: intrinsic peroxidase catalytic activity and its application for biocatalysis and biosensing.

A combined hydrothermal/hydrogen reduction method has been developed for the mass production of helical carbon nanotubes (HCNTs) by the pyrolysis of acetylene at 475 °C in the presence of Fe(3)O(4) nanoparticles. The synthesized HCNTs have been characterized by high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction analysis, vibrating sample magnetometry, and contact-angle measurements. The as-prepared helical-structured carbon nanotubes have a large specific surface area and high peroxidase-like activity. Catalysis was found to follow Michaelis-Menten kinetics and the HCNTs showed strong affinity for both H(2)O(2) and 3,3',5,5',-tetramethylbenzidine (TMB). Based on the high activity, the HCNTs were firstly used to develop a biocatalyst and amperometric sensor. At pH 7.0, the constructed amperometric sensor showed a linear range for the detection of H(2)O(2) from 0.5 to 115 µM with a correlation coefficient of 0.999 without the need for an electron-transfer mediator. Because of their low cost and high stability, these novel metallic HCNTs represent a promising candidate as mimetic enzymes and may find a wide range of new applications, such as in biocatalysis, immunoassay, and environmental monitoring.

Ultrasensitive electrochemical immunoassay based on cadmium ion-functionalized PSA@PAA nanospheres.

A simple strategy for sensitive detection of human IgG using cadmium ions-functionalized polymer nanospheres as the label is presented. The polymer nanosphere consisted of hard poly-styrene core and biocompatible poly (acrylic acid) (PAA) shell. The carboxyl groups of hydrophilic shell were used to chelated with the cadmium ions, and then conjugate with antibody (Ab(2)) to fabricate metal ions marked bioconjugates as the label in immunoassay. For constructing the matrix of the immunosensor, the PAA-functionalized carbon nanotubes were used to modify disposable screen printed electrodes for the immobilization of antibody (Ab(1)). After sandwich immunoreaction, differential pulse voltammetry was used to oxidize the conjuncted cadmium for the detection of antigen. The obtained results provided a linear response range from 0.1 to 35.0 pg/mL human IgG with a lower detection limit of 0.06 pg/mL, which is prominently improved in comparison with conventional immunoassay. The usage of the chelation reaction offers a simple and convenient route for the preparation of metallo-immunoassay labels, and also avoids the complicated and time-consuming dissolving of metal component for ultrasensitive determination. This approach is expected to have wide applications in protein diagnostics and bioanalysis in the future.

Horseradish peroxidase-functionalized gold nanoparticle label for amplified immunoanalysis based on gold nanoparticles/carbon nanotubes hybrids modified biosensor.

This paper describes the combination of electrochemical immunosensor using gold nanoparticles (GNPs)/carbon nanotubes (CNTs) hybrids platform with horseradish peroxidase (HRP)-functionalized gold nanoparticle label for the sensitive detection of human IgG (HIgG) as a model protein. The GNPs/CNTs nanohybrids covered on the glass carbon electrode (GCE) constructed an effective antibody immobilization matrix and made the immobilized biomolecules hold high stability and bioactivity. Enhanced sensitivity was obtained by using bioconjugates featuring HRP labels and secondary antibodies (Ab(2)) linked to GNPs at high HRP/Ab(2) molar ratio. The approach provided a linear response range between 0.125 and 80ng/mL with a detection limit of 40pg/mL. The immunosensor showed good precision, acceptable stability and reproducibility and could be used for the detection of HIgG in real samples, which provided a potential alternative tool for the detection of protein in clinical laboratory.

CdTe quantum dots as probes for near-infrared fluorescence biosensing using biocatalytic growth of Au nanoparticles.

A near-infrared (NIR) fluorescence sensing strategy for glucose and xanthine has been developed based on the interaction between CdTe quantum dots (QDs) and biocatalytic generated Au nanoparticles. The fluorescence of CdTe QDs is modulated by changing concentration of AuCl4- and Au nanoparticles during the growth process of Au nanoparticles. Two cases were considered. In the first case, the glucose oxidase (GOx) catalyzes the oxidation of glucose to generate H2O2. Under the catalysis of Au nanoparticles seeds, the AuCl4- is reduced by the H2O2 to form the Au nanoparticles. In the second case, the xanthine oxidase acts as the reducing reagents to reduce AuCl4- forming Au nanoparticles. The interaction between CdTe quantum dots (QDs), AuCl4-, and Au nanoparticles resulted in the fluorescence changes of CdTe QDs, allowing the detection of glucose and xanthine. The effects of Au nanoparticles and AuCl4- on the fluorescence of CdTe QDs were discussed. A model was developed to explain the mechanism of the CdTe QDs fluorescence changes by biocatalytic growth of Au nanoparticles. The difference in the Stern-Volmer quenching constant between AuCl4- and Au nanoparticles is the dominant factor for the CdTe QDs fluorescence changes. The developed method provides low limits of detection, wide linear ranges, and detection wavelengths in the NIR region and can be easily extended to other substrate/oxidase systems.

Versatile immunosensor using CdTe quantum dots as electrochemical and fluorescent labels.

A versatile immunosensor using CdTe quantum dots as electrochemical and fluorescent labels has been developed for sensitive protein detection. This sandwich-type sensor is fabricated on an indium tin oxide chip covered with a well-ordered gold nanoparticle monolayer. Gel imaging systems were successfully introduced to develop a novel high-efficient optical immunoassay, which could perform simultaneous detection for the samples with a series of different concentrations of a target analyte. The linear range of this assay was between 0.1 and 500 ng/mL, and the assay sensitivity could be further increased to 0.005 ng/mL with the linear range from 0.005 to 100 ng/mL by stripping voltammetric analysis. The immunosensor showed good precision, high sensitivity, acceptable stability, and reproducibility and could be used for the detection of real sample with consistent results in comparison with those obtained by the ELISA method.