Gelation Mechanism of Erythromycin Ethylsuccinate During Crystallization

In this paper, the gelation mechanism of erythromycin ethylsuccinate(EES) during crystallization is investigated for the first time. The generated semisolid gel-like phase exhibited a 3D fibrillar network morphology and the typical rheological properties of gels. The fibers inside the gel-like phase were confirmed to be new types of EES solvates using powder X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, and gas chromatography. The gelation and crystallization regions in EES-1-propanol solid–liquid phase diagram were determined. Analyses of solvent parameters showed that moderate solvent polarity may promote EES gelation. Fourier transform infrared spectra, nuclear magnetic resonance spectra, and scanning electron microscopy analyses indicated that through intermolecular hydrogen bonds, EES and solvent molecules assembled into fibers via crystallographic mismatch branching growth. The fibers intertwined into a 3D network microstructure and formed a gel-like phase, completely immobilizing the solution.

Long-time evolution of charged grains in plasma under harmonic external force and after being withdrawn

Evolution of the charged grains in a two-dimensional dusty plasma under a spatially harmonic external force,in particular,their long-time behaviors after the force has been withdrawn,is studied by using molecular dynamics simulation.Under an external force and a grain–grain interaction force,initially homogeneously distributed grains can reach a quasistationary state in the form of a disk crystal.After the external force is withdrawn,the disk moves initially with its size and shape nearly unchanged until it rapidly stops moving,and eventually the disk grain rotates like a vortex.The time needed to reach the final state increases with the strength of the initial external force increasing.

Current research and future directions of melatonin’s role in seed germination

Seed germination is a complex process regulated by internal and external factors.Melatonin(N-acetyl-5-meth-oxytryptamine)is a ubiquitous signaling molecule,playing an important role in regulating seed germination under normal and stressful conditions.In this review,we aim to provide a comprehensive overview on melatonin’s effects on seed germination on the basis of existing literature.Under normal conditions,exogenous high levels of melatonin can suppress or delay seed germination,suggesting that melatonin may play a role in maintaining seed dormancy and preventing premature germination.Conversely,under stressful conditions(e.g.,high salinity,drought,and extreme temperatures),melatonin has been found to accelerate seed germination.Melatonin can modulate the expression of genes involved in ABA and GA metabolism,thereby influencing the balance of these hormones and affecting the ABA/GA ratio.Melatonin has been shown to modulate ROS accumulation and nutrient mobilization,which can impact the germination process.In conclusion,melatonin can inhibit germination under normal conditions while promoting germination under stressful conditions via regulating the ABA/GA ratios,ROS levels,and metabolic enzyme activity.Further research in this area will deepen our understanding of melatonin’s intricate role in seed germination and may contribute to the development of improved seed treatments and agricultural practices.

Biomineralization-inspired copper-cystine nanoleaves capable of laccase-like catalysis for the colorimetric detection of epinephrine

Recently,many efforts have been dedicated to creating enzyme-mimicking catalysts to replace natural enzymes in practical fields.Inspired by the pathological biomineralization behaviour of L-cystine,in this study,we constructed a laccase-like catalyst through the co-assembly of L-cystine with Cu ions.Structural analysis revealed that the formed catalytic Cu-cystine nanoleaves(Cu-Cys NLs)possess a Cu(I)-Cu(II)electron transfer system similar to that in natural laccase.Reaction kinetic studies demonstrated that the catalyst follows the typical Michaelis-Menten model.Compared with natural laccase,the Cu-Cys NLs exhibit superior stability during long-term incubation under extreme pH,high-temperature or high-salt conditions.Remarkably,the Cu-Cys NLs could be easily recovered and still maintained 76%of their activity after 8 cycles.Finally,this laccase mimic was employed to develop a colorimetric method for epinephrine detection,which achieved a wider linear range(9–455μmol·L^(−1))and lower limit of detection(2.7μmol·L^(−1)).The Cu-Cys NLs also displayed excellent specificity and sensitivity towards epinephrine in a test based on urine samples.