Probing DNA hybridization efficiency and single base mismatch by X-ray photoelectron spectroscopy

Construction of antifouling zwitterionic membranes by facile multi-step integration method

Membrane fouling during the use of separation membrane has always been the main reason for the degradation of membrane performance. The traditional solution is complicated and inefficient, so we proposed multi-step integration method to prepare antifouling zwitterionic poly(aryl ether sulfone) (PAES-Z-x) ultrafiltration (UF) membrane with higher efficiency. We designed and synthesized a bisphenol precursor containing tertiary amine groups, which could provide reactive sites for grafting zwitterionic group. Afterwards, the zwitterionic modified UF membrane was prepared by graft copolymerization and non-solvent-induced phase separation (NIPS). The morphology, hydrophilicity, water flux and rejection of the PAES-Z-x membrane could be optimized by tuning zwitterion content. The hydration layer formed by zwitterions effectively reduced the adsorption of proteins and endowed the membrane good antifouling properties. The resulting membrane showed the pure water flux increased (up to 311 L m^-2h^-1 bar^-1), high bovine serum albumin (BSA) rejection (97%) and good water flux recovery ratio (FRR) (82.8%). Zwitterionic antifouling PAES UF membrane prepared by a simple and effective method provided a new direction for improving PAES UF membrane's antifouling performance.

Intermediate accumulation and toxicity reduction during the selective photoelectrochemical process of atrazine in complex water bodies

Selective removal of atrazine (ATZ) in wastewater and clarification of the degradation intermediate-toxicity correlation are of great importance. A newly molecularly imprinted, {001} facets-exposed TiO₂ (MI-TiO_2,001) photoanode with strong catalytic and selective ability was designed. ATZ was selectively removed from pesticide wastewater, reaching 1.9 µg L^-1, approximately 1/10 of the concentration achieved with nonselective treatment. This selective removal originated from the preferential adsorption and enrichment of ATZ onto MI-TiO_2,001. The highly specific recognition relied on the halogen bond and strong hydrogen bond formed between the Cl atom and triazine ring π orbital of ATZ and the surface -OH group of MI-TiO_2,001 as well as the recognition of MI-TiO_2,001 to the shape and size of ATZ. The specific interaction leads to different accumulations of intermediates. The correlation of intermediate and toxicity was also discussed. Aquatic toxicity was rapidly reduced through the direct dealkylation path, and due to the accumulation of highly toxic 2‑hydroxy-4-ethylamino-6-isopropylamino-s-triazine, there will be transient fluctuations via the dechlorination-hydroxylation path first. The final product was identified as nearly nontoxic cyanuric acid, the selective accumulation of which indicated that there was almost 100% removal of aquatic toxicity and cytotoxicity with only 9.8% removal of total organic carbon. This work provides new insight into the correlation of pollutant degradation intermediates and changes in toxicity.

Investigation of organic impurity and its occurrence in industrial waste salt produced by physicochemical process

Industrial waste salt is classified as hazardous waste to the environment. The organic impurity and its occurrence in industrial waste salt affect the salt resource utilization. In this paper, composition quantitative analysis, XRD, TG-DSC, SEM/FIB-SEM coupled with EDS, FTIR, XPS and GC-Ms were chosen to investigate the organic impurity and its occurrence in industrial waste salt. The organic impurities owe small proportion (1.77%) in the specimen and exhibit weak thermal stability within the temperature of 600°C. A clear definition of organic impurity, including 11 kinds of organic compounds, including aldehyde, benzene and its derivatives etc., were detected in the industrial waste salt. These organic impurities, owing (C-O/C-O-C, C-OH/C = O, C–C/CH_x/C = C etc.)-containing function group substance, are mainly distributed both on the surface and inside of the salt particles. Meanwhile, the organic substance may combine with metal cations (Ni²⁺, Mg²⁺, Cu²⁺ etc.) through functional groups, such as hydroxide, carbonyl etc., which increases its stability in the industrial waste salt. These findings provide comprehensive information for the resource utilization of industrial waste salt from chemical industry etc.

Colorimetric biosensing of nopaline synthase terminator using Fe3O4@Au and hemin-functionalized reduced graphene oxide

In this paper, we present a simple and label-free colorimetric biosensor for detection of the nopaline synthase (NOS) terminator in genetically modified (GM) plants. The "signal on" colorimetric biosensor was developed using a nanocomposite consisted of gold nanoparticles doped magnetic Fe₃O₄ nanoparticles (Fe₃O₄@Au NP), capture probe DNA (cDNA), and hemin-functionalized reduced graphene oxide nanosheets (H-GN). The nanocomposite was successfully prepared by means of Au-S bonds and the strong π interactions between cDNA and H-GN. The sensing approach is based on the excellent peroxidase-mimicking activity of H-GN and its different electrostatic interactions with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). In presence of the target NOS, the cDNA in the nanocomposite will hybridize with its complementary sequence, and form dsDNA structure. Due to the weak π interactions between dsDNA and H-GN, a portion of H-GN will be released from the surface of Fe₃O₄@Au NPs and transferred into solution. After magnetic separation was performed, the supernatant was incubated with 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂. The released H-GN can catalyze the oxidation reaction of TMB and turn the colorless solution blue. This "signal-on" colorimetric biosensor shows a broad linear range of 0.5-100 nM for the target NOS, with a 0.19 nM detection limit. The application of the biosensor for determination of NOS segments in samples of GM and non-GM tomatoes shows that it can discriminate between GM and non-GM plants. The reliability of the method for samples of NOS-spiked GM tomato suggests satisfactory recoveries in the range of 93.6%-94.2%.

A Quasi-direct LC-MS/MS-based Targeted Proteomics Approach for miRNA Quantification via a Covalently Immobilized DNA-peptide Probe

MicroRNAs (miRNAs) play a vital role in regulating gene expression and are associated with a variety of cancers, including breast cancer. Their distorted and unique expression is a potential marker in clinical diagnoses and prognoses. Thus, accurate determination of miRNA expression levels is a prerequisite for their applications. However, the assays currently available for miRNA detection typically require pre-enrichment, amplification and labeling steps, and most of the assays are only semi-quantitative. Therefore, we developed a quasi-direct liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based targeted proteomics approach to quantify target miRNA by innovatively converting the miRNA signal into the mass response of a reporter peptide via a covalently immobilized DNA-peptide probe. Specifically, the probe containing the targeted proteomics-selected substrate/reporter peptide, GDRAVQLGVDPFR/AVQLGVDPFR, and the DNA sequence complementary to the target miRNA (i.e., miR-21) was first immobilized on APMTS modified silica nanoparticles using PDITC. After the immobilized probe was recognized and hybridized with the target miRNA, the excess probe was degraded using MBN and followed by a trypsin digestion of the hybrids. The reporter peptide was released and quantified using LC-MS/MS. The obtained LOQ was 5 pM. Finally, the developed assay was used for the quantitative analysis of miR-21 in breast cells and tissue samples.

Effect of co-axially hybridized gene targets on hybridization efficiency of microarrayed DNA probes

The effect of relative size of two co-axially hybridized gene targets on the hybridization efficiency was studied for two DNA probe configurations and various probe concentrations. Each of two sets of microarrayed probes contained a pair of DNA probes and a pair of their complementary samples labeled with two distinct fluorescent dyes. The sequence of each probe is especially designed so that two targets are simultaneously complementary to two adjacent sections of the probe. The molecular steric effect on the hybridization efficiency is investigated by comparing the dye signals between configurations of one-target and two-target hybridization scenarios. The results show that a low probe concentration gives better hybridization efficiency and the first-hybridization conducted by a shorter-size DNA target improves the hybridization efficiency of the second target coupling onto the same probe.