Antibacterial activity and synergistic antibiotic mechanism of trialdehyde phloroglucinol against methicillin-resistant Staphylococcus aureus.

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) has become a critical global concern. Identifying new anti-S. aureus agents or therapeutic strategies are urgently needed to treat S. aureus infection. The present study investigated the antibacterial activity of 16 phenolic compounds against MRSA, four of which exhibited antibacterial activity. Their antibacterial activities increased in a dose-dependent manner but showed different responses with the extension of treatment time. Trialdehyde phloroglucinol (TPG) and 2-nitrophloroglucinol (NPG) maintained stable antibacterial activity; however, that of dichlorophenol and myricetin decreased rapidly over 24 hr of treatment. Checkerboard and time-kill assays indicated that TPG and NPG exhibited strong synergistic antibacterial activities with penicillin or bacitracin. Microscopic observation and membrane integrity analysis showed that the combination of TPG and penicillin destroyed the MRSA cell membrane, resulting in the leakage of intracellular biomacromolecules, marked changes in surface zeta potential, and the collapse of membrane potential. Moreover, the combination significantly decreased penicillinase activity and penicillin-binding protein 2a mRNA expression, inhibiting MRSA growth. Taken together, these results demonstrated that the combination of the phloroglucinol derivative TPG and penicillin has significant synergistic anti-MRSA activity and can serve as a potential therapeutic strategy to treat MRSA infections.

Synthesis of Group VIII Magnetic Transition-Metal-Doped Monolayer MoSe2.

The limitation on the spintronic applications of van der Waals layered transition-metal dichalcogenide semiconductors is ascribed to the intrinsic nonmagnetic feature. Recent studies have proved that substitutional doping is an effective route to alter the magnetic properties of two-dimensional transition-metal dichalcogenides (TMDs). However, highly valid and repeatable substitutional doping of TMDs remains to be developed. Herein, we report group VIII magnetic transition metal-doped molybdenum diselenide (MoSe2) single crystals via a one-pot mixed-salt-intermediated chemical vapor deposition method with high controllability and reproducibility. The high-angle annular dark-field scanning transmission electron microscopy studies further confirm that the sites of Fe are indeed substitutionally incorporated into the MoSe2 monolayer. The Fe-doped MoSe2 monolayer with a concentration from 0.93% to 6.10% could be obtained by controlling the ratios of FeCl3/Na2MoO4. Moreover, this strategy can be extended to create Co(Ni)-doped MoSe2 monolayers. The magnetic hysteresis (M-H) measurements demonstrate that group VIII magnetic transition-metal-doped MoSe2 samples exhibit room-temperature ferromagnetism. Additionally, the Fe-doped MoSe2 field effect transistor shows n-type semiconductor characteristics, indicating the obtainment of a room-temperature dilute magnetic semiconductor. Our approach is universal in magnetic transition-metal substitutional doping of TMDs, and it inspires further research interest in the study of related spintronic and magnetoelectric applications.

Design, synthesis and biological evaluation of novel pleuromutilin derivatives as potent anti-MRSA agents targeting the 50S ribosome.

A series of novel pleuromutilin derivatives were designed and synthesized with 1,2,4-triazole as the linker connected to benzoyl chloride analogues under mild conditions. The in vitro antibacterial activities of the synthesized derivatives against four strains of Staphylococcus aureus (MRSA ATCC 43300, ATCC 29213, AD3 and 144) were tested by the broth dilution method. Most of the synthesized derivatives displayed potent activities, and 22-(3-amino-2-(4-methyl-benzoyl)-1,2,4-triazole-5-yl)-thioacetyl)-22-deoxypleuromutilin (compound 12) was found to be the most active antibacterial derivative against MRSA (MIC = 0.125 µg/mL). Furthermore, the time-kill curves showed compound 12 had a certain inhibitory effect against MRSA in vitro. The in vivo antibacterial activity of compound 12 was further evaluated using MRSA infected murine thigh model. Compound 12 exhibited superior antibacterial efficacy than tiamulin. It was also found that compound 12 had no significant inhibitory effect on the proliferation of RAW264.7 cells. Compound 12 was further evaluated in CYP450 inhibition assay and showed moderate inhibitory effect on CYP3A4 (IC50 = 3.95 µM). Moreover, seven candidate compounds showed different affinities with the 50S ribosome by SPR measurement. Subsequently, binding of compound 12 and 20 to the 50S ribosome was further investigated by molecular modeling. Three strong hydrogen bonds were formed through the interaction of compound 12 and 20 with 50S ribosome. The binding free energy of compound 12 and 20 with the ribosome was calculated to be -10.7 kcal/mol and -11.66 kcal/mol, respectively.

High-order superlattices by rolling up van der Waals heterostructures.

Two-dimensional (2D) materials1,2 and the associated van der Waals (vdW) heterostructures3-7 have provided great flexibility for integrating distinct atomic layers beyond the traditional limits of lattice-matching requirements, through layer-by-layer mechanical restacking or sequential synthesis. However, the 2D vdW heterostructures explored so far have been usually limited to relatively simple heterostructures with a small number of blocks8-18. The preparation of high-order vdW superlattices with larger number of alternating units is exponentially more difficult, owing to the limited yield and material damage associated with each sequential restacking or synthesis step8-29. Here we report a straightforward approach to realizing high-order vdW superlattices by rolling up vdW heterostructures. We show that a capillary-force-driven rolling-up process can be used to delaminate synthetic SnS2/WSe2 vdW heterostructures from the growth substrate and produce SnS2/WSe2 roll-ups with alternating monolayers of WSe2 and SnS2, thus forming high-order SnS2/WSe2 vdW superlattices. The formation of these superlattices modulates the electronic band structure and the dimensionality, resulting in a transition of the transport characteristics from semiconducting to metallic, from 2D to one-dimensional (1D), with an angle-dependent linear magnetoresistance. This strategy can be extended to create diverse 2D/2D vdW superlattices, more complex 2D/2D/2D vdW superlattices, and beyond-2D materials, including three-dimensional (3D) thin-film materials and 1D nanowires, to generate mixed-dimensional vdW superlattices, such as 3D/2D, 3D/2D/2D, 1D/2D and 1D/3D/2D vdW superlattices. This study demonstrates a general approach to producing high-order vdW superlattices with widely variable material compositions, dimensions, chirality and topology, and defines a rich material platform for both fundamental studies and technological applications.

Tunable luminescence evolution and energy transfer behavior of Na3Sc2(PO4)3:Ce3+/Tb3+/Eu3+ phosphors.

A series of color-tunable emitting Na3Sc2(PO4)3:Ce3+/Tb3+/Eu3+ (NSPO) phosphors were prepared by a combination of hydrothermal synthesis and low temperature calcination. The phase structure, photoluminescence and energy transfer properties of the samples were studied in detail. The tunable colors were obtained by co-doping the Tb3+ ions into the NSPO:Ce3+ or NSPO:Eu3+ phosphors with varying concentrations. Under UV excitation, the energy transfers from Tb3+ to Eu3+ in the NSPO host occurred mainly via a dipole-dipole mechanism, and the critical distances of the ion pairs (R c) was calculated to be 17.94 Å by the quenching concentration method. And that, the emission colors of the NSPO:Tb3+,Eu3+ phosphors could be adjusted from green through yellow to red because of the energy transfer from Tb3+ to Eu3+. Based on its good photoluminescence properties and abundant emission colors, the NSPO:Ce3+/Tb3+/Eu3+ phosphors might be promising as potential candidates for solid-state lighting and display fields.