Ethylene-induced NbMYB4L is involved in resistance against tobacco mosaic virus in Nicotiana benthamiana.

Several MYB transcription factors are known to play important roles in plant resistance to environmental stressors. However, the mechanism governing the involvement of MYBs in regulating tobacco mosaic virus (TMV) resistance in plants is still unclear. In this study, we found that not only is Nicotiana benthamiana MYB4-like involved in defence against TMV, but also that the ethylene pathway participates in MYB4L-mediated resistance. Transcription of NbMYB4L was up-regulated in N. benthamiana infected with TMV. Silencing of NbMYB4L led to intensified TMV replication, whereas overexpression of NbMYB4L induced significant resistance to TMV. Transcription of NbMYB4L was greater in 1-aminocyclopropanecarboxylic acid (ACC, ethylene precursor)-pretreated plants but lower when the ethylene signalling pathway was blocked during TMV infection. Gene expression analysis showed that the transcription of NbMYB4L was largely suppressed in ETHYLENE INSENSITIVE 3-like 1(EIL1)-silenced plants. The results of electrophoretic mobility shift assay and chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) experiments indicated that NbEIL1 could directly bind to two specific regions of the NbMYB4L promoter. Furthermore, a luciferase assay revealed that NbEIL1 significantly induced the reporter activity of the MYB4L promoter in N. benthamiana. These results point to NbEIL1 functioning as a positive regulator of NbMYB4L transcription in N. benthamiana against TMV. Collectively, our work reveals that EIL1 and MYB4L constitute a coherent feed-forward loop involved in the robust regulation of resistance to TMV in N. benthamiana.

[Sensing of Cu²âº Based on Fenton Reaction and Unmodified Gold Nanoparticles].

Heavy metal pollution has received great attentions in recent years. The traditional methods for heavy metal detection rely on the expensive laboratory instruments and need time-consuming preparation steps; therefore, it is urgent to develop quick and highly sensitive new technologies for heavy metal detection. The colorimetric method based on the gold nanoparticles (AuNPs) features with simple operation, high sensitivity and low cost, therefore, enabling it widely concerned and used in the environmental monitoring, food safety and chemical and biological sensing fields. This work developed a simple, rapid and highly sensitive strategy based on the Fenton reaction and unmodified AuNPs for the detection of Cu²âº in water samples. The hydroxyl radical ( · OH) generated by the Fenton reaction between the Cu²âº and sodium ascorbate (SA) oxidized the single stranded DNA (ssDNA) attached on the AuNPs surface into variable sequence fragments. The cleavage of ssDNA induced the aggregation of AuNPs in a certain salt solution, therefore, resulting in the changes on the absorbance of solution. The assay conditions were optimized to be pH value of 7.9, 11 mg · L⁻¹ ssDNA, 8 mmol · L⁻¹ SA and 70 mmol · L⁻¹ NaCl. Results showed that the absorbance ratio values at the wavelengths of 700 and 525 nm (A700/A525) were linearly correlated with the Cu²âº concentrations. The linear detection range was 0.1-10.0 µmol · L⁻¹ with a detection limit of 24 nmol · L⁻¹ (3σ). Spiked recoveries ranged from 87%-120% in three sorts of water, including drinking water, tap water and lake water, which confirmed that the potentials of the proposed assay for Cu²âº detection in reality.

Gold nanorod-covered kanamycin-loaded hollow SiO2 (HSKAu(rod)) nanocapsules for drug delivery and photothermal therapy on bacteria.

A hybrid bactericidal material, gold nanorod-covered kanamycin-loaded hollow SiO(2) (HSKAu(rod)) nanocapsules, is constructed. The hybrid material combines the features of a chemical drug with photothermal physical sterilization which decreases the dosage of broad-spectrum antibiotic and the physical damage of biological systems. Hollow SiO(2) nanocapsules are used as carriers for drug delivery. The nanocapsules load a model drug, kanamycin, and are covered with gold nanorods to avoid drug leakage and realize photothermal treatment. The sterilizing effect on the bacterial strain is investigated by incubating E. coli BL21 with the hybrid nanocapsules and irradiating under near-infrared light (NIR) for 20 min. A bactericidal effect, i.e., a sterilizing rate of 53.47%, is achieved for the HSKAu(rod) nanocapsules under NIR irradiation, with respect to a net sum sterilizing rate of 34.49% for the individual components of the HSKAu(rod) nanocapsules, e.g., carrier nanocapsules, chemical sterilization of kanamycin and physical sterilization due to the gold nanorods under NIR irradiation. It is demonstrated that the combination of chemical drug and physical sterilization results in an obvious synergistic effect and makes the sterilization more effective. This novel hybrid has great potential as an adjuvant therapeutic alternative material for sterilization or even for the control of disease.

Fenton's reagent-tuned DNA-templated fluorescent silver nanoclusters as a versatile fluorescence probe and logic device.

A label-free strategy based on the Fenton reaction with DNA-templated silver nanoclusters (DNA-Ag NCs) as a probe is demonstrated for the sequential detection of Cu(2+), ascorbic acid (AA) and H(2)O(2). Cu(2+) causes a structural change of the DNA template in DNA-Ag NCs to resist the environmental quenching and emit stronger fluorescence. The addition of AA in the presence of Cu(2+) results in a further fluorescence increase of the DNA-Ag NCs. Interestingly, an even higher fluorescence enhancement is recorded by introducing Cu(2+) into the DNA-Ag NCs-AA probing system. The fluorescence turn-on probe offers detection limits of 3 nM for Cu(2+) and 7 nM for AA. Thereafter, the addition of H(2)O(2) generates hydroxyl radicals from the Fenton reaction, which induces cleavage of the DNA template, leading to fluorescence quenching of the DNA-Ag NCs. This facilitates H(2)O(2) detection. Moreover, based on the DNA-templated fluorescent silver nanoclusters and Fenton reaction, a multiple logic gate system, including AND and a three-input logic gate, is constructed, with Cu(2+), AA and H(2)O(2) as inputs, and the fluorescence intensity of the DNA-Ag NCs probe as output.

Label-free colorimetric sensing of ascorbic acid based on Fenton reaction with unmodified gold nanoparticle probes and multiple molecular logic gates.

A label-free strategy based on Fenton reaction with unmodified gold nanoparticles (AuNPs) as probe is demonstrated for ascorbic acid (AA) sensing. AuNPs is stable in the presence of single stranded DNA (ssDNA) which prevents salt-induced aggregation of AuNPs in solution. The hydroxyl free radicals generated by Fenton reaction lead to ssDNA cleavage into different sequence fragments which induce aggregation of AuNPs to produce a red-to-blue color change. As an efficient biological antioxidant, AA could effectively scavenge free radicals to avoid the cleavage of ssDNA, so that it prevents color change of the AuNPs solution. Thus, the color change of AuNPs in the presence and absence of AA provides a new approach for the detection of AA. The absorbance ratio at two wavelengths, A(670)/A(520), decreases linearly with AA content within 1-15 µM, giving rise to a detection limit of 0.3 µM and a RSD of 2.8% (10 µM). The color display of AuNPs solution makes it feasible for the estimation of AA content by naked eye visualization. Moreover, based on Fenton reaction and unmodified gold nanoparticles, a multiple logic gate system includes two logic operations, i.e., INHIBIT and NOR, has been designed with small molecules (AA, l-cysteine, glutathione) as inputs and the colorimetric changes of AuNPs solution as outputs.

The inhibition of fluorescence resonance energy transfer between quantum dots for glucose assay.

Fluorescence resonance energy transfer (FRET) between two quantum dots of different sizes causes fluorescence quenching. Hereby a binding site pre-blocking approach is proposed to avoid this effect. Pre-binding of glucose on the donor occupies the binding sites and thus blocks resonance energy transfer between the two quantum dots, protecting the fluorescence from being quenched. A glucose assay is developed based on this approach. The glucose content is correlated with the fluorescence difference in the absence and in the presence of glucose. In practice, Green QDs-Con A conjugates are used as donors and Red QDs-NH(2)-glu conjugates as acceptors to form FRET system. The inhibition of fluorescence quenching is then measured in the presence of glucose. A linear calibration graph is achieved within 0.1-2.0 mmolL(-1), along with a detection limit of 0.03 mmolL(-1) and a RSD of 2.1% (1.0 mmolL(-1)). 91-105% of glucose in serum and urine samples is recovered. It is worth mentioning that the present glucose assay approach also generates a fluorescence chromatic difference imaging, and the color display clearly identifies the glucose contents by visual detection with a distinguishing ability of ca. 0.5 mmolL(-1). The present approach can potentially be used for the clinical determination of glucose in biological samples which can be further developed into a glucose sensor.

[DSC and temperature-dependent infrared spectroscopic study of hydrogen-bonded liquid crystal complexes].

The hydrogen-bonded liquid crystalline complexes based on 4', 4-bipyridine and 4-(trans-4-propylcyclohexyl) benzoic acid and trans-4-(trans-4-propylcyclohexyl)cyclohexyl carboxylic acid assigned as PCBA-BPy and PCCA-BPy were prepared and measured by polarized optical microscopy (POM), differential scanning calorimeter (DSC) and temperature-dependent FTIR It was found that PCBA-BPy and PCCA-BPy exhibited both smectic and nematic phase while all of their predecessors showed no smectic phase. The temperature-dependent FTIR studies revealed that the hydrogen bonding in complex PCBA-BPy was very different from that in PCCA-BPy. The wave number of C=O band had an obvious change at the crystal 1-crystal 2 transition but almost didn't change at smectic-nematic and nematic-isotropic transition; while in PCCA-BPy, it showed no sudden changes but shift to 1 709 cm(-1) gradually with the increase in temperature. The results from temperature-dependent FTIR studies also revealed that when the temperature was higher than the clearing point of the complexes, both of the complexes decomposed partially.