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The precise control of Z and E configurations of the carbon-carbon double bond in alkene synthesis has long been a fundamental challenge in synthetic chemistry, even more pronounced when simultaneously striving to achieve enantioselectivity [(Z, R), (Z, S), (E, R), (E, S)]. Moreover, enantiopure non-natural a-amino acids are highly sought after in organic and medicinal chemistry. In this study, we report a ligand-controlled stereodivergent synthesis of non-natural a-quaternary amino acids bearing trisubstituted alkene moieties in high yields with excellent enantioselectivity and Z/E selectivities. This success is achieved through a palladium/copper-cocatalyzed three-component assembly of readily available aryl iodides, allenes, and aldimine esters by simply tuning the chiral ligands of the palladium and copper catalysts. [ABSTRACT FROM AUTHOR]

Dust acoustic waves (DAWs) in plasmas are influenced by many plasma parameters, such as, ion temperature, electron number density, nonthermal and nonextensive parameters, and dust cyclotron frequency. The plasma system is described by plasma fluid equations. The Zakharov–Kuznetsov equation and instability growth rate of DAWs have been obtained by reductive perturbation method and small‐k$$ k $$ expansion method, respectively. The effects of plasma parameters on the linear dispersion relation, phase velocity, amplitude, width, soliton energy, and three‐dimensional instability of DAWs have been carried out. It is obvious that the incremental nonextensive (nonthermal) parameter leads to the shrinking (incremental) soliton energy and phase velocity. These results are useful for understanding dusty plasma dynamics with Cairns–Tsallis electrons in planetary rings. [ABSTRACT FROM AUTHOR]

To date, the increase in reactive oxygen species (ROS) production for effectual photodynamic therapy (PDT) treatment still remains challenging. In this study, a facile and effective approach is utilized to coat mesoporous silica (mSiO2) shell on the ligand-free upconversion nanoparticles (UCNPs) based on the LiYF4 host material. Two kinds of mesoporous silica-coated UCNPs (UCNP@mSiO2) that display green emission (doped with Ho3+) and red emission (doped with Er3+), respectively, were successfully synthesized and well characterized. Three photosensitizers (PSs), merocyanine 540 (MC 540), rose bengal (RB), and chlorin e6 (Ce6), with the function of absorption of green or red emission, were selected and loaded into the mSiO2 shell of both UCNP@mSiO2 nanomaterials. A comprehensive study for the three UCNP@mSiO2/PS donor/acceptor pairs was performed to investigate the efficacy of fluorescence resonance energy transfer (FRET), ROS generation, and in vitro PDT using a MCF-7 cell line. ROS generation detection showed that as compared to the oleate-capped and ligand-free UCNP/PS pairs, the UCNP@mSiO2/PS nanocarrier system demonstrated more pronounced ROS generation due to the UCNP@mSiO2 nanoparticles in close vicinity to PS molecules and a higher loading capacity of the photosensitizer. As a result, the three LiYF4 UCNP@mSiO2/PS nanoplatforms displayed more prominent therapeutic efficacies in PDT by using in vitro cytotoxicity tests.

Cysteinyl‐tRNA synthetase (CysRS) catalyzes the aminoacylation reaction of cysteine to its cognate tRNACys in the first step of protein translation. It is found that CysRS is different from other aaRSs as it transfers cysteine without the need for an editing reaction, which is not applicable in the case of serine despite the similarity in their structures. Surprisingly, the reasons why CysRS has high amino acid specificity are not clear yet. In this research, the binding configurations of Cys‐AMP and its near‐cognate amino acid Ser‐AMP with CysRS are compared by Molecular Dynamics (MD). The results reveal that CysRS screens the substrate Cys‐AMP to a certain extent in the process of combination and recognition, thus providing a guarantee for the high selectivity of the next reaction. While Ser‐AMP is in a folded state in CysRS. In the meanwhile, the interaction between Cys‐AMP and Zn963 in CysRS is much stronger than Ser‐AMP. The substrate‐assisted aminoacylation mechanism in CysRS is also explored by Quantum Mechanics/Molecular Mechanics (QM/MM) modeling. According to the QM/MM potential energies, the energy barrier of TSCys‐AMP is 91.75 kJ/mol, while that of TSSer‐AMP is close to 150 kJ/mol. Based on thermochemistry calculations, it is found that the product of Cys‐AMP is more stable than the reactant. In contrast, Ser‐AMP has a reactant that is more stable than its product. As a result, it reflects that the specificity of CysRS originates from both the kinetic and thermodynamical perspectives of the reaction. Our investigations demonstrate comprehensively on how CysRS recognizes and catalyzes the substrate Cys‐AMP, hoping to provide some guidance for researchers in this area. [ABSTRACT FROM AUTHOR]

To date, the increase in reactive oxygen species (ROS) production for effectual photodynamic therapy (PDT) treatment still remains challenging. In this study, a facile and effective approach is utilized to coat mesoporous silica (mSiO2) shell on the ligand-free upconversion nanoparticles (UCNPs) based on the LiYF4 host material. Two kinds of mesoporous silica-coated UCNPs (UCNP@mSiO2) that display green emission (doped with Ho3+) and red emission (doped with Er3+), respectively, were successfully synthesized and well characterized. Three photosensitizers (PSs), merocyanine 540 (MC 540), rose bengal (RB), and chlorin e6 (Ce6), with the function of absorption of green or red emission, were selected and loaded into the mSiO2 shell of both UCNP@mSiO2 nanomaterials. A comprehensive study for the three UCNP@mSiO2/PS donor/acceptor pairs was performed to investigate the efficacy of fluorescence resonance energy transfer (FRET), ROS generation, and in vitro PDT using a MCF-7 cell line. ROS generation detection showed that as compared to the oleate-capped and ligand-free UCNP/PS pairs, the UCNP@mSiO2/PS nanocarrier system demonstrated more pronounced ROS generation due to the UCNP@mSiO2 nanoparticles in close vicinity to PS molecules and a higher loading capacity of the photosensitizer. As a result, the three LiYF4 UCNP@mSiO2/PS nanoplatforms displayed more prominent therapeutic efficacies in PDT by using in vitro cytotoxicity tests. [ABSTRACT FROM AUTHOR]