Search

Huanglongbing (HLB) is a devastating citrus disease that causes significant financial losses in the citrus industry. However, there is no cure by current control strategies. Damaged soils were observed in citrus orchards; root lesions and nematodes were observed in HLB-affected citrus tree roots. Bacillus subtilis (B. subtilis) makes a great contribution to pathogen control and has the potential to control HLB. Purpureocillium lilacinum (P. lilacinum) and Trichoderma harzianum (T. harzianum) can kill pathogenic organisms such as nematodes and Phytophthora spp. to protect roots. Restoration of the damaged soils and improvement of citrus root growth through the introduction of soil amendments and biocontrol agents (containing B. subtilis, P. lilacinum, and T. harzianum) may provide an efficient approach to controlling HLB. Results revealed that soil properties such as soil pH and organic matter content were improved. After three months of combination treatment of soil amendment and biocontrol agent through root drenches, the citrus grew new roots and its leaves changed from yellow to green. The percentage of HLB-positive citrus trees—Orah, Tangerine, and Navel Orange—decreased from 90 to 0%, 87.5% to 21.88%, and 81.25% to 0% over three years, respectively. Furthermore, the productivity of HLB-affected orchards was restored, and both production and quality saw significant improvement. These results suggested that combining soil remediation and biocontrol improved soil quality and protected citrus root growth, thus effectively controlling HLB. [ABSTRACT FROM AUTHOR]

l-nucleosides were the most important antiviral lead compounds because they can inhibit viral DNA polymerase and DNA synthesis of many viruses, whereas they may lead to mutations in DNA replication and cause genomic instability. In this study, we reported the replicative bypass of l-deoxynucleosides in recombinant DNA by restriction enzyme–mediated assays to examine their impact on DNA replication in vitro and in E. coli cells. The results showed that a template l-dC inhibited Taq DNA polymerase reaction, whereas it can be bypassed by Vent (exo-) DNA polymerase as well as in cell replication, inserting correct nucleotides opposite l-dC. l-dG can be bypassed by Taq DNA polymerase and in E. coli cells, maintaining insertion of correct incoming nucleotides, and l-dG induced mutagenic replication by Vent (exo-) DNA polymerase. In contrast, l-dA can induced mutagenic replication in vitro and in E. coli cells. MD simulations were performed to investigate how DNA polymerase affected replicative bypass and mutations when d-nucleosides replaced with l-nucleosides. This study will provide a basis for the ability to assess the cytotoxic and mutagenic properties of the l-nucleoside drugs. [ABSTRACT FROM AUTHOR]

Atrazine is one of the most used herbicides in China. It is a persistent organic pollutant but has been widely used on Chinese farmlands for a long time. To assess its dietary and ecological risks to human and environment, in this study, atrazine residues were extracted with acetonitrile and then plant samples were detected with gas chromatography coupled with mass spectrometry (GC-MS) and soil samples were determined with gas chromatography coupled with nitrogen-phosphorus detector (GC-NPD). The limit of quantification (LOQ) of the method was 0.01 mg/kg for all matrices. The recoveries ranged from 82.0 to 105.4% for plant samples and 75.6 to 85.6% for soil samples. The final residues of atrazine in all plant samples were lower than LOQ. Dietary risk assessment suggested that under good agricultural practices (GAP) conditions, intake of atrazine from apples, grapes, and tea would exhibit an acceptably low health risk on consumers. However, the final residues of atrazine in soil samples were <0.01–9.2 mg/kg, and the half-lives were 2.0–9.1 days. Based on the species sensitivity distribution (SSD) model, the potential affected fraction (PAF) of atrazine in soil samples ranges from 0.01 to 65.8%. Atrazine residues in 43.1% soil samples were higher than 0.11 mg/kg, which was the hazardous concentration for 5% of species (HC5) of atrazine in soil. These results suggested that the ecological risks of atrazine in apples, grapes, and tea garden soil would exhibit a high risk on environmental species even under the same GAP conditions. This study could provide guidance for comprehensive risk assessment of atrazine properly used in apple, grape, and tea gardens. [ABSTRACT FROM AUTHOR]

A series of self-supporting three-dimensional (3D) hexagonal-tungsten trioxide/reduced graphene oxide (h-WO3/rGO) nanorod arrays photocatalyst are synthesized by simple hydrothermal method without substrate. By selecting cationic dye methylene blue (MB), amphoteric dye rhodamine B (RhB) and anionic dye methyl orange (MO) as model organic pollutants, the experiments indicate that the 3D h-WO3/rGO photocatalyst shows a synergistic effect of adsorption and photocatalysis under visible light irradiation for the removal of MB and RhB. WrG1 which adding 1 wt% graphene oxide (GO) during synthesis demonstrates optimal adsorption and degradation activity and the bandgap energy (Eg) of WrG1 is 2.02 eV. Adsorption removal efficiency of MB, RhB and MO are 96.0%, 62.4% and 10.9% and the total removal efficiency of MB, RhB and MO are 99.3%, 84.8% and 18.3% by 0.3 g/L WrG1, respectively. Moreover, holes (h+) were the main active species for the photocatalytic degradation of organic pollutants. This work revealed the adsorption and photocatalysis activity of three different charge dyes on the h-WO3/rGO, which facilitates in understanding the removal mechanism in combination with other analytical methods and the impact of photocatalyst chargeability on degradation of organic pollutants. The visible light bifunctional catalyst h-WO3/rGO as adsorbent and photocatalyst presents a great potential in removal cationic and amphoteric organic pollutant from wastewater without additional treatment under ambient conditions. [ABSTRACT FROM AUTHOR]

A novel method, based on modified silver nanoparticles, for high-throughput visual detection of heavy metal ions in polyvinyl chloride (PVC) products was developed including a key pretreatment process in which tetrahydrofuran was used to dissolve PVC powder samples quickly. Heavy metal ions were successfully transferred from THF to the aqueous phase by the liquid–liquid extraction method during the pretreatment procedures. Then, enriched Cu2+, Mn2+, and Cr3+ were detected by three kinds of silver nanoparticles (4-MBA-AgNPs, 4-MBA-MA-AgNPs, and 4-NBT/4-MBA-AgNPs) using naked eyes and microplate reader, respectively. The visual detection limits of Cu2+, Mn2+, and Cr3+ were 1.0 × 10−6 M, 1.0 × 10−7 M, and 1.0 × 10−6 M, while the detection limits of Cu2+, Mn2+, and Cr3+ were 2.5 × 10−8 M, 5.0 × 10−8 M, and 5.0 × 10−8 M using microplate reader, respectively. Apparently, the proposed method could provide a potent means in the practical detection of heavy metal ions in PVC products with advantages of low-cost, rapid, high-throughput, and on-site detection. [ABSTRACT FROM AUTHOR]

Dissipation behavior, final residue, and risk assessment of butralin in soybean, green soybean, plant, and soil were investigated. Butralin residues were extracted with acetonitrile and then soybean samples were detected with gas chromatography-mass spectrometer (GC-MS) and soil samples were determined with GC with nitrogen phosphorous detector (GC-NPD). The limit of quantification (LOQ) of the method was 0.01 mg/kg for soybean, green soybean, plant, and soil. Average recoveries ranged from 90.4 ~ 98.2% for green soybean, 86.2 ~ 86.6% for soybean, 86.0 ~ 98.8% for plant, and 85.0 ~ 106.8% for soil. The relative standard deviations (RSDs) were 2.0 ~ 7.2% for green soybean, 2.0 ~ 3.0% for soybean, 3.1 ~ 8.1% for plant, and 1.8 ~ 6.6% for soil. Half-lives of butralin in soil samples varied in the range of 11-22 days. At harvest time, final residues of butralin in soybean and green soybean were lower than LOQ. Risk assessment demonstrated that, at recommended dosage and frequency, butralin would not induce significant harm on humans. The study could be used as a quantitative basis for application of butralin on soybean. [ABSTRACT FROM AUTHOR]

The authors describe a colorimetric assay for the determination of As(III) in aqueous solution using citrate capped gold nanoparticles (AuNPs) which, in the presence of As(III), undergo aggregation due to the interaction of citrate ion with As(III). This results in an easily detectable color change from wine-red to blue. The ratio of the absorbances at 661 and 519 nm is linearly related to the As(III) concentration in the 4 to 100 ppb range, with a detection limit as low as 1.8 ppb (at 3σ) which is below the guideline value of 10 ppb. The method is rather simple in that it does not require the surface of the AuNPs to be modified. It was successfully applied to the determination of As(III) in spiked drinking water where it gave adequate recoveries. [ABSTRACT FROM AUTHOR]

In the present work, capillary electrophoresis (CE) was used for the first time for the simultaneous analysis of azodicarbonamide (ADA) and semicarbazide (SEM), and the capillary electrophoresis separation conditions, extraction agents, and derivatization conditions were investigated. In 20 mmol L sodium tetraborate, 30 mmol L β-cyclodextrin (β-CD), 17 % isopropanol ( v/ v), and 25 mmol L sodium dodecyl sulfate (SDS) running buffer, ADA and SEM previously derivatized with 9-fluorenylmethyl chloroformate (FMOC) were separated in less than 25 min with good sensitivity. The linear ranges were 8.3 × 10∼6.6 × 10 mmol L and 1.9 × 10∼3.4 × 10 mmol L, and detection limits ( S/ N = 10) were 0.5 and 0.15 mg kg for ADA and SEM, respectively. The proposed method was successfully applied for the simultaneous analysis of ADA and SEM in five flour samples with satisfactory recovery data from 88.0 to 93.0 % for ADA and 98.0 to 106.0 % for SEM, indicating the valuable potential application of this method for food analysis. [ABSTRACT FROM AUTHOR]

Currently known immunoassays for aflatoxins (AFs) usually are not capable of simultaneous determination of total AFs (i.e., aflatoxin B, aflatoxin B, aflatoxin G, aflatoxin G) due to the lack of group-specific antibodies. We are presenting here a colorimetric method for determination of total AFs by exploiting the Hg(II) ion-mediated aggregation of lysine-functionalized gold nanoparticles (Lys-AuNPs). AFs bind Hg(II) ion to form stable complexes, and this prevents the Hg(II) induced aggregation of Lys-AuNPs. Hence, the color change of solutions of AuNPs that occurs after aggregation of the AuNPs is suppressed. This effect was exploited to design a method for quantitation of AFs that can be detected by UV-Vis spectrophotometry (by measuring the ratio of absorbances at 725 nm and 525 nm), and even with bare eyes. The method has a very low detection limit (1.1 ppb) and is highly selective for AFs over other mycotoxins. Colorimetric analysis of rice samples by this method gave results that were in good agreement with those obtained by HPLC. To the best of our knowledge, this is the first method for visual detection of total AFs based on the distance-dependent optical properties of AuNPs. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The colorimetric assay for neomycin presented here is based on melamine-modified gold nanoparticles (mel-AuNPs) and the finding that hydrogen bonding between melamine and neomycin results in the aggregation of mel-AuNPs. This results in a change in the color of the solution from wine red to blue and in a red-shift of the absorption maximum of the mel-AuNPs. The concentration of neomycin can be determined by spectrophotometry. The ratio of absorptions at 680 nm and 520 nm is linearly related to the logarithm of the concentration of neomycin in the 0.1 to 5.0 nM range and in the 5 to 100 nM range, with regression coefficients of 0.997 and 0.999, respectively. The detection limit (at an S/N ratio of 3) is 30 pM. This is far below the usual safety limit. The method was applied to the detection of trace levels of neomycin in milk samples and gave recoveries between 98 and 105 %. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A new method is presented for the visual detection of dicyandiamide (DCD). Gold nanoparticles (AuNPs) capped with gallic acid (GA) were synthesized in a single step at room temperature, using GA as both the reducing agent and stabilizer. In the presence of DCD, the hydrogen-bonding interaction between GA and DCD induces the aggregation of AuNPs, associated with a color change from red to gray that can be observed with bare eye. DCD could be quantified by photometry as the red shift of the maximal absorption band is linearly related to the logarithm of concentration of DCD in the 0.1 to 500 μM concentration range, with a regression coefficient of 0.9987 and a 80 nM detection limit (at an SNR of 3). The proposed method was successfully applied to the detection of DCD in spiked dairy samples. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Coal-tar pitch (CP) is a promising carbon raw material for producing needle coke, carbon fiber etc. During processing, the H/C ratio, ash content, and quinoline insoluble (QI) in the CP are the key factors that influence the material preparation. In this study, NMP was selected to extract CP first; then [BMIM]Cl/NMP mixed solvent was used; and finally a series of ionic liquids (ILs) mixtures with NMP were developed for the extraction of CP to obtain the refined pitch. The extracts were analyzed via elemental analysis, TGA, FT-IR, and C-NMR. Results indicate that different NMP/IL mass ratios or different kinds of ILs have impact on the extraction yield. The relationship of the hydrogen to carbon (H/C) ratio changed with different solvents and QI extracts were obtained. Results showed that the H/C ratios changed little between NMP extracts and could be adjusted by changing the NMP/ILs mass ratio or using different ILs. The extracts are suitable for preparation mesophase pitch because of no ash content, low QI, and appropriate H/C ratios. As a result, NMP can be used to refine pitch. In addition, [BMIM]Cl is good mixed with NMP for CP extraction, because it can obtain a relatively high yield under the same extraction conditions. [ABSTRACT FROM AUTHOR]

We are presenting an electrochemical immunosensor for the determination of the β-agonist and food additive ractopamine. A glassy carbon electrode (GCE) was modified with gold nanoparticles and a film of a composite made from poly(arginine) and multi-walled carbon nanotubes. Antibody against ractopamine was immobilized on the surface of the modified GCE which then was blocked with bovine serum albumin. The assembly of the immunosensor was followed by electrochemical impedance spectroscopy. Results demonstrated that the semicircle diameter increases, indicating that the film formed on the surface hinders electron transfer due to formation of the antibody-antigen complex on the modified electrode. Under optimal conditions, the peak current obtained by differential pulse voltammetry decreases linearly with increasing ractopamine concentrations in the 0.1 nmol•L to 1 μmol•L concentration range. The lower detection limit is 0.1 nmol•L. The sensor displays good stability and reproducibility. The method was applied to the analysis of spiked swine feed samples and gave satisfactory results. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A newly-developed method of complete separation and sensitive determination of o-, m-, and p-aminobenzoic acid isomers was achieved by combining open-tubular columns for capillary electrochromatography (OT-CEC) and online sample stacking. In this study, spherical gold nanoparticles were modified by a covalent attachment of mono-6-thio-β-cyclodextrin, and OT-CEC was formed by immobilizing cyclodextrin-modified gold nanoparticles (CD-AuNP) on prederivatized 3-mercaptopropyl-trimethoxysilane fused-silica capillaries. Based on the theory of moving chemical reaction boundary, effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were optimized. The optimized separations were carried out in 58 mmol/L HAc buffer at pH 3.0 using a capillary coated with CD-AuNP, while the optimized concentration was carried out in 50 mmol/L disodium hydrogen phosphate (pH 9.5). The linear ranges for m-, p-, and o-aminobenzoic acid were from 5.0 × 10-0.1, 5.0 × 10-0.1 and 1.0 × 10-0.1 mmol/L, respectively. And the detection limits (S/N = 3) were as low as 8.22 × 10, 8.21 × 10, and 3.76 × 10 mmol/L for m-, p-, and o-aminobenzoic acid, respectively. The run-to-run, day-to-day, and column-to-column reproducibilities of migration time were satisfactory with relative standard deviation values of less than 4.5 % in all cases. This method was successfully used in determining procaine hydrochloride injection sample with recoveries in the range of 96.1-106.6 % and relative standard deviations less than 5.0 %. [ABSTRACT FROM AUTHOR]

Supramolecular chirality and molecular self-assembly are important and interesting phenomena in living and non-living systems. In this work, supramolecular chirality of achiral pseudoisocyanine (PIC) J-aggregates was successfully induced by D-, L-phenylalanine (Phe) and other amino acids in NaCl solution. The chiral J-aggregates showed a characteristic, induced circular dichroism (ICD) in the visible region of J-band chromophore which depends on the absolute configuration, concentration and side groups of α-amino acids, as well as temperature. The atomic force microscopy images indicated that the J-aggregates exist in large bundles of entangled nanofibers, and the observed ICD might result from the macroscopic helical arrangement of the assemblies. [ABSTRACT FROM AUTHOR]

In this essay, some discussions and comments about the paper entitled “Can the decay rate of 32P be changed by mechanic motion?” (Ding et al., Science in China Series B: Chemistry (Chinese version), 2008, 38(11):1035–1037) are given. It was strongly suggested that its experimental methods, data calculations and conclusion should be reconsidered. After the data were recalculated, the new results supported that the chiral mechanic motion could induce the changes of radioactive half life. [ABSTRACT FROM AUTHOR]

The changes of decay rates of radionuclide 111In (electron capture) and 32P (β decay) induced by external mechanic motion are studied. The results indicate that, in the external circular rotation in clockwise and anticlockwise centrifuge on Northern Hemisphere (radius 8 cm, 2000 r/min), the half life of 111In compared with the referred (2.83 d) is decreased at 2.83% and increased at 1.77%, respectively; the half life of 32P compared with the referred (14.29 d) is decreased at 3.78% and increased at 1.75%, respectively. When the clockwise and anticlockwise rotations increase to 4000 r/min, the half life of 111In is decreased at 11.31% and increased at 6.36%, respectively; the half life of 32P is decreased at 10.08% and increased at 4.34%, respectively. When the circular rotation is removed, the decay rates of 111In and 32P, return back to the referred, respectively. It is found that the external circular rotations in clockwise and anticlockwise centrifuge selectively increased and decreased the decay rates of 111In and 32P, respectively, and the effects are strongly dependent on the strength of circular rotation. It is suggested that these effects may be caused by the chiral interaction. [ABSTRACT FROM AUTHOR]

Under different conditions, oligonucleotides can form several alternative DNA structures such as duplex, triplex and quadruplex. All these structures can interact with ethidium bromide (EB) and make its fluorescence intensity change. The fluorescence spectra and other related parameters provided by static fluorescence techniques showed that the interaction mechanisms between EB and these structures were not always the same. Among them, B type duplex and triplex DNA adopt an intercalative mode when binding to the EB, which has a relatively high efficiency of energy transfer and the fluorescence of EB cannot be quenched easily. While for the parallel duplex DNA, the interaction mode is an outside binding in which energy transfer can hardly happen and its fluorescence intensity as well as Stern-Volmer constant is almost the same to the free EB. For the quadruplex, the binding mechanism to EB is more complex. Results from the energy transfer and quenching studies indicate that the two interaction modes noted above probably coexist at the same time. [ABSTRACT FROM AUTHOR]