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Kainoid synthases are key enzymes in the biosynthesis of kainoids. Kainoids, as represented by DA and KA, are a class of naturally occurring non-protein amino acids with strong neurotransmitter activity in the mammalian central nervous system. Marine algae kainoid synthases include PnDabC from diatoms, which synthesizes domoic acid (DA), and DsKabC and GfKabC from red algae, which synthesize kainic acid (KA). Elucidation of the catalytic mechanism of kainoid synthases is of great significance for the rational design of better biocatalysts to promote the industrial production of kainoids for use in new drugs. Through modeling, molecular docking, and molecular dynamics simulations, we investigated the conformational dynamics of kainoid synthases. We found that the kainoid synthase complexes showed different stability in the simulation, and the binding and catalytic processes showed significant conformational transformations of kainoid synthase. The residues involved in specific interactions with the substrate contributed to the binding energy throughout the simulation process. Binding energy, the relaxed active pocket, electrostatic potential energy of the active pocket, the number and rotation of aromatic residues interacting with substrates during catalysis, and the number and frequency of hydrogen bonds between the individual functional groups revealed the structure–activity relationships and affected the degree of promiscuity of kainoid synthases. Our research enriches the understanding of the conformational dynamics of kainoid synthases and has potential guiding significance for their rational design. [ABSTRACT FROM AUTHOR]

We explored the effect of occupational stigma on work engagement, basing our research on conservation of resources theory. Frontline hotel employees (N = 286) in China completed an online survey. Analysis of the results showed that occupational stigma was negatively related to work engagement, and occupational identity and emotional exhaustion both played mediating roles in this relationship. These findings enrich the research on the antecedents of work engagement and provide practical implications for related management practice. [ABSTRACT FROM AUTHOR]

We report the direct formation of dicarboxylate-based coordination polymer glasses through thermal dehydration. The rearrangement of the coordination networks caused by dehydration was monitored by in situ powder X-ray diffraction, infrared spectroscopy, and synchrotron X-ray characterizations. The microporosity and mechanical properties of these glasses were investigated. [ABSTRACT FROM AUTHOR]

Crystalline triazine‐based covalent organic frameworks (COFs) are aromatic nitrogen‐rich porous materials. COFs typically show high thermal/chemical stability, and are promising for energy applications, but often require harsh synthesis conditions and suffer from low crystallinity. In this work, we propose an environmentally friendly route for the synthesis of crystalline COFs from CO2 molecules as a precursor. The mass ratio of CO2 conversion into COFs formula unit reaches 46.3 %. The synthesis consists of two steps; preparation of 1,4‐piperazinedicarboxaldehyde from CO2 and piperazine, and condensation of the dicarboxaldehyde and melamine to construct the framework. The CO2‐derived COF has a 3‐fold interpenetrated structure of 2D layers determined by powder X‐ray diffraction, high‐resolution transmission electron microscopy, and select‐area electron diffraction. The structure shows a high Brunauer–Emmett–Teller surface area of 945 m2 g−1 and high stability against strong acid (6 M HCl), base (6 M NaOH), and boiling water over 24 hours. Post‐modification of the framework with oxone has been demonstrated to modulate hydrophilicity, and it exhibits proton conductivity of 2.5×10−2 S cm−1 at 85 °C, 95 % of relative humidity. [ABSTRACT FROM AUTHOR]

Crystalline triazine‐based covalent organic frameworks (COFs) are aromatic nitrogen‐rich porous materials. COFs typically show high thermal/chemical stability, and are promising for energy applications, but often require harsh synthesis conditions and suffer from low crystallinity. In this work, we propose an environmentally friendly route for the synthesis of crystalline COFs from CO2 molecules as a precursor. The mass ratio of CO2 conversion into COFs formula unit reaches 46.3 %. The synthesis consists of two steps; preparation of 1,4‐piperazinedicarboxaldehyde from CO2 and piperazine, and condensation of the dicarboxaldehyde and melamine to construct the framework. The CO2‐derived COF has a 3‐fold interpenetrated structure of 2D layers determined by powder X‐ray diffraction, high‐resolution transmission electron microscopy, and select‐area electron diffraction. The structure shows a high Brunauer–Emmett–Teller surface area of 945 m2 g−1 and high stability against strong acid (6 M HCl), base (6 M NaOH), and boiling water over 24 hours. Post‐modification of the framework with oxone has been demonstrated to modulate hydrophilicity, and it exhibits proton conductivity of 2.5×10−2 S cm−1 at 85 °C, 95 % of relative humidity. [ABSTRACT FROM AUTHOR]