Gymnodimines (GYMs), belonging to cyclic imines (CIs), are characterized as fast-acting toxins, and may pose potential risks to human health and the aquaculture industry through the contamination of sea food. The existing detection methods of GYMs have certain defects in practice, such as ethical problems or the requirement of complicated equipment. As novel molecular recognition elements, aptamers have been applied in many areas, including the detection of marine biotoxins. However, GYMs are liposoluble molecules with low molecular weight and limited numbers of chemical groups, which are considered as “challenging” targets for aptamers selection. In this study, Capture-SELEX was used as the main strategy in screening aptamers targeting gymnodimine-A (GYM-A), and an aptamer named G48nop, with the highest KD value of 95.30 nM, was successfully obtained by screening and optimization. G48nop showed high specificity towards GYM-A. Based on this, a novel aptasensor based on biolayer interferometry (BLI) technology was established in detecting GYM-A. This aptasensor showed a detection range from 55 to 1400 nM (linear range from 55 to 875 nM) and a limit of detection (LOD) of 6.21 nM. Spiking experiments in real samples indicated the recovery rate of this aptasensor, ranging from 96.65% to 109.67%. This is the first study to report an aptamer with high affinity and specificity for the challenging marine biotoxin GYM-A, and the new established aptasensor may be used as a reliable and efficient tool for the detection and monitoring of GYMs in the future.
Four new species, namely E. (Euodynerus) carinatus sp. nov. (Sichuan), E. (Pareuodynerus) deqinensis sp. nov. (Yunnan), E. (P.) ferrugineus sp. nov. (Yunnan), and E. (P.) similinipanicus sp. nov. (Yunnan), are described and illustrated. Euodynerus (P.) strigatus (Radoszkowski) is newly recorded from China. A key to the Chinese species of Euodynerus is given.
Although aptamers are widely used in various biomedical areas as novel molecular recognition elements, they are degraded by nucleases in biological fluids due to short single-stranded DNA (ssDNA) or RNA oligonucleotides. Research shows that this problem can be solved by circularizing aptamers with circular ligases, which can catalyze the intramolecular ligation of ssDNA templates with 5'-phosphate and 3'-hydroxyl groups. Herein, a thermostable ssDNA ligase was successfully expressed and purified for subsequent aptamer cyclization. The purified ligase showed good circularization activity for substrates with different lengths and had much higher circularization efficiency than T4 RNA ligase 1. Moreover, circularization reaction conditions, such as the concentration of MnCl2, enzyme and betaine, were studied to ascertain the optimal conditions for the catalytic reaction. The results indicated that the highest ligating activity occurred at MnCl2, enzyme and betaine concentrations of 1.25–2.5 mM, 0.02 mM and 1 М, respectively. Based on these, templates with different terminal nucleotides were tested to assess the sequence dependence of ligase. The results show that the efficiency of circularization is sequence dependent, in which 5'-G and 3'-T are the terminal nucleotides most favored by ligase. Finally, the stability asssy further confirmed that the circular aptamer was more stable than its linear form in biological fluids.
In this paper, 20 species of the genus Stenodynerus are reviewed and identified from China, including five new species: Stenodynerus
ninglangensis Ma & Li, sp. n., Stenodynerus
reflexus Ma & Li, sp. n., Stenodynerus
similibaronii Ma & Li, sp. n., Stenodynerus
strigatus Ma & Li, sp. n., and Stenodynerus
tenuilamellatus Ma & Li, sp. n., and five new records: Stenodynerus
baronii Giordani Soika, Stenodynerus
bluethgeni van der Vecht, Stenodynerus
picticrus (Thomson), Stenodynerus
pullus Gusenleitner and Stenodynerus
nepalensis Giordani Soika. The five new species are described and illustrated in detail. Moreover, the diagnostic characters of all new records and known species from China are provided, with a key to the Chinese species of Stenodynerus.
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