Southwest University

About: Southwest University is a education organization based out in Chongqing, China. It is known for research contribution in the topics: Population & Bombyx mori. The organization has 29772 authors who have published 27755 publications receiving 409441 citations. The organization is also known as: Southwest University in Chongqing & SWU.

A fluorescence aptasensor based on semiconductor quantum dots and MoS2 nanosheets for ochratoxin A detection

Abstract: Molybdenum disulfide (MoS 2 ) nanosheet has been extensively investigated as an effective fluorescence quencher. However, its combination with semiconductor quantum dots (QDs) for the development of an aptasensor based on the fluorescence quenching has not be explored. Herein, a novel aptamer-CdTe QDs-MoS 2 nanosheets fluorescence quenching system was developed for the detection of ochratoxin A (OTA) with QDs as donors and MoS 2 nanosheets as quenchers. The QDs-conjugated aptamers with the linear conformation can assemble on the MoS 2 nanosheets, causing the fluorescence quenching. In the presence of OTA, the aptamers wrap around the targets to form folded structures with a low affinity to the nanosheets, thus resulting in an OTA concentration-dependent restoration of the fluorescence intensity. The platform shows good specificity, a limit of detection of 1.0 ng/mL and a dynamic range over 1.0–1000 ng/mL in laboratory buffers. The platform is also successfully used to detect OTA in spiked red wine samples, verifying its feasibility in real sample analysis. The QDs-MoS 2 nanosheets fluorescence quenching system could be easily adapted to measure other biomolecules by changing the thiol-modified aptamer.

Nitrogen and carbon source-sink relationships in trees at the Himalayan treelines compared with lower elevations

Abstract: No single hypothesis or theory has been widely accepted for explaining the functional mechanism of global alpine/arctic treeline formation. The present study tested whether the alpine treeline is determined by (1) the needle nitrogen content associated with photosynthesis (carbon gain); (2) a sufficient source-sink ratio of carbon; or (3) a sufficient C-N ratio. Nitrogen does not limit the growth and development of trees studied at the Himalayan treelines. Levels of non-structural carbohydrates (NSC) in trees were species-specific and site-dependent; therefore, the treeline cases studied did not show consistent evidence of source/carbon limitation or sink/growth limitation in treeline trees. However, results of the combined three treelines showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of a tree influence its tissue NSC concentrations and the carbon balance; therefore, we suggest that the persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration, a sufficiently high sugar:starch ratio, and a balanced carbon source-sink relationship.

A nanozyme-based cascade colorimetric aptasensor for amplified detection of ochratoxin A

Abstract: Colorimetric assays have been widely developed for the detection of toxin ochratoxin A (OTA), but most of them suffer from moderate sensitivity when they are adopted for the detection of trace OTA in a complicated food matrix. For the purpose of overcoming this issue, an innovative cascade reaction-based colorimetric aptasensor was developed for the achievement of high sensitivity. The biotin-labelled OTA aptamer was immobilized onto streptavidin magnetic beads by means of the biotin-streptavidin reaction. With OTA binding to its aptamer, the structural switching of the aptamer results in the release of the alkaline phosphatase-labelled oligonucleotide, which is partially complementary to the aptamer. Following the magnetic separation, the cascade reaction is initiated through the enzymatic conversion of ascorbic acid-2-phosphate into ascorbic acid. Subsequent to that, the generated ascorbic acid reduces MnO2 nanosheets to Mn2+ ions, accordingly destroying the oxidase-mimicking activity of MnO2 nanosheets. In consequence, it is not possible to oxidize 3,3',5,5'-tetramethylbenzidine (TMB), a substrate for oxidase, with Mn2+ for the production of the blue colour product (TMB Ox). With the increasing amount of OTA, a colour change occurs from blue to colourless. The cascade reaction has the potential of greatly amplifying the detection signal, together with remarkably improving the sensitivity, making this colorimetric sensor a universal and promising platform for the highly sensitive detection of mycotoxins in the field of public food safety monitoring.