Three-dimensional (3D) covalent organic frameworks (COFs) are rare because there is a limited choice of organic building blocks that offer multiple reactive sites in a polyhedral geometry. Here, we synthesized an organic cage molecule ( Cage-6-NH 2 ) that was used as a triangular prism node to yield the first cage-based 3D COF, 3D-CageCOF-1 . This COF adopts an unreported 2-fold interpenetrated acs topology and exhibits reversible dynamic behavior, switching between a small-pore ( sp ) structure and a large-pore ( lp ) structure. It also shows high CO 2 uptake and captures water at low humidity (<40%). This demonstrates the potential for expanding the structural complexity of 3D COFs by using organic cages as the building units.
Fatty acids are important nutrients contained in bee pollen and vary greatly depending on the floral species. In this study, 20 species of monofloral bee pollen from China were collected to analyze fatty acid composition. Fatty acids were identified and quantified using gas chromatography-mass spectrometry with selected ion monitor (GC-MS/SIM) and compared with reference standards of 37 fatty acid methyl esters. Our results reveal that in virtually all bee pollen samples, a broad variety of fatty acids ranging from 11 to 20 types were identified. Palmitic acid, stearic acid, α-linolenic acid, linoleic acid, eicosenoic acid and erucic acid occurred in all bee pollen samples. In addition, the presence of nervonic acid in bee pollen is a novel finding, with an average level of 0.21 mg/g. Perfil de ácidos grasos en 20 especies de polen monofloral de abejas de ChinaLos ácidos grasos presentes en el polen de abeja son un nutriente importante cuya composició n varía dependiendo de las especies florales. En este estudio, se analizó la composició n en ácidos grasos de 20 especies de polen monofloral de abeja china. Los ácidos grasos fueron identificados y cuantificados usando la técnica de cromatografía de gases-espectrometría de masas con monitoreo de iones seleccionados (GC-MS/SIM por sus siglas en inglés) y comparados con estándares de referencia de 37 metil ésteres de ácidos grasos. Nuestros resultados revelan que se identificaron, virtualmente en todas las muestras de polen de abeja, una gran variedad de ácidos grasos, que van desde los 11 hasta los 20 tipos. Los ácidos palmítico, esteárico, α-linoleico, linoleico, eicosenoico y docosenoico se observaron en todas las muestras de polen de abeja. Además, la presencia del ácido nervó nico en el polen de abeja es un nuevo descubrimiento, con un nivel medio de 0,21 mg/g.
Multiple-replicon resistance plasmids have become important carriers of resistance genes in Gram-negative bacteria, and the evolution of multiple-replicon plasmids is still not clear. Here, 56 isolates of Klebsiella isolated from different wild animals and environments between 2018 and 2020 were identified by phenotyping via the micro-broth dilution method and were sequenced and analyzed for bacterial genome-wide association study. Our results revealed that the isolates from non-human sources showed more extensive drug resistance and especially strong resistance to ampicillin (up to 80.36%). The isolates from Malayan pangolin were particularly highly resistant to cephalosporins, chloramphenicol, levofloxacin, and sulfamethoxazole. Genomic analysis showed that the resistance plasmids in these isolates carried many antibiotic resistance genes. Further analysis of 69 plasmids demonstrated that 28 plasmids were multiple-replicon plasmids, mainly carrying beta-lactamase genes such as blaCTX–M–15, blaCTX–M–14, blaCTX–M–55, blaOXA–1, and blaTEM–1. The analysis of plasmids carried by different isolates showed that Klebsiella pneumoniae might be an important multiple-replicon plasmid host. Plasmid skeleton and structure analyses showed that a multiple-replicon plasmid was formed by the fusion of two or more single plasmids, conferring strong adaptability to the antibiotic environment and continuously increasing the ability of drug-resistant isolates to spread around the world. In conclusion, multiple-replicon plasmids are better able to carry resistance genes than non-multiple-replicon plasmids, which may be an important mechanism underlying bacterial responses to environments with high-antibiotic pressure. This phenomenon will be highly significant for exploring bacterial resistance gene transmission and diffusion mechanisms in the future.
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