A Rapid Fluorescence Sensor for the Direct Quantification of Rongalite in Foodstuffs.

Rongalite was reported illegally used as a food additive for bleaching purposes and improving the tenderness of foodstuffs, which may endanger public health. At present, rongalite was mostly detected by indirect methods via derivatization or determining its decomposition products. In this study, we developed a new fluorescence sensor for the direct quantification of rongalite based on the principles: (1) dopamine reacts with resorcinol and generates strong fluorophore (azamonardine); (2) rongalite could inhibit the production of fluorophores and then result in lower fluorescence intensity. Hence, the rongalite concentration was inversely proportional to fluorescence intensity of fluorophore. Several crucial reaction conditions of fluorescence sensor were further optimized, such as dopamine and resorcinol concentration, pH values, and reaction time. Under the optimal conditions, the limit of detection of fluorescence sensor was 0.28-0.38 µg/g in vermicelli, wheat and rice powder samples, exhibiting almost 3.5-fold improvement compared to that of lateral flow immunoassay. Moreover, the detection time was substantially decreased to 20 min. The recoveries in spiked samples were 80.7-102.1% with a coefficient of variation of less than 12.6%. In summary, we developed a direct, high throughput, selective and accurate fluorescence sensor that poses a promising application for the rapid detection of rongalite in foodstuffs.

AuNPs-based lateral flow immunoassay for point-of-needs analysis of four neonicotinoids in tea samples: Effects of grinding degrees, solvent types and contents on extraction efficiency.

The higher extraction efficiency of analytes is crucial for developing immunoassays with high accuracy. Here, we evaluated the extraction efficiency of neonicotinoids in tea samples in terms of grinding degrees, extraction solvents types and contents. Fragments for fresh tea leaves (1 g, 5-10 mm2) or tea powder (1 g, 35 mesh) for commercial tea was extracted with 100 % methanol. The extraction (1 mL) was diluted 10-fold with buffer solution, and then submitted to gold nanoparticles-based lateral flow immunoassay. This optimal extraction protocol exhibited a higher extraction efficiency (72.4-99.3 %) for the positive neonicotinoids samples. The cut-off values of lateral flow immunoassay were 0.325 or 0.65 µg/g, 0.3 or 0.45 µg/g, 0.3 or 0.45 µg/g, 0.03 or 0.06 µg/g for thiamethoxami, clothianidin, acetamiprid and midacloprid in fresh tea leaves and commercial tea. In summary, this proposed lateral flow immunoassay can be used as the point-of-needs analysis method for four neonicotinoids in tea.

Metabolism of the Genus Guyparkeria Revealed by Pangenome Analysis.

Halophilic sulfur-oxidizing bacteria belonging to the genus Guyparkeria occur at both marine and terrestrial habitats. Common physiological characteristics displayed by Guyparkeria isolates have not yet been linked to the metabolic potential encoded in their genetic inventory. To provide a genetic basis for understanding the metabolism of Guyparkeria, nine genomes were compared to reveal the metabolic capabilities and adaptations. A detailed account is given on Guyparkeria's ability to assimilate carbon by fixation, to oxidize reduced sulfur, to oxidize thiocyanate, and to cope with salinity stress.

The impact of global dimming on crop yields is determined by the source-sink imbalance of carbon during grain filling.

Global dimming reduces incident global radiation but increases the fraction of diffuse radiation, and thus affects crop yields; however, the underlying mechanisms of such an effect have not been revealed. We hypothesized that crop source-sink imbalance of either carbon (C) or nitrogen (N) during grain filling is a key factor underlying the effect of global dimming on yields. We presented a practical framework to assess both C and N source-sink relationships, using data of biomass and N accumulation from periodical sampling conducted in field experiments for wheat and rice from 2013 to 2016. We found a fertilization effect of the increased diffuse radiation fraction under global dimming, which alleviated the negative impact of decreased global radiation on source supply and sink growth, but the source supply and sink growth were still decreased by dimming, for both C and N. In wheat, the C source supply decreased more than the C sink demand, and as a result, crops remobilized more pre-heading C reserves, in response to dimming. However, these responses were converse in rice, which presumably stemmed from the more increment in radiation use efficiency and the more limited sink size in rice than wheat. The global dimming affected source supply and sink growth of C more significantly than that of N. Therefore, yields in both crops were dependent more on the source-sink imbalance of C than that of N during grain filling. Our revealed source-sink relationships, and their differences and similarities between wheat and rice, provide a basis for designing strategies to alleviate the impact of global dimming on crop productivity.