Plasmon-hybridization-induced optical torque between twisted metal nanorods.

We present a numerical study of optical torque between two twisted metal nanorods due to the angular momentum of the electromagnetic field emerging from their plasmonic coupling. Our results indicate that the interaction optical torque on the nanorods can be strongly enhanced by their plasmon coupling, which highly depends on not only the gap size but also the twisted angle between the nanorods. The behaviors of the optical torque are different between two plasmon coupling modes: hybridized bonding and anti-bonding modes with different resonances. The rotations of the twisted nanorods with the bonding and anti-bonding mode excitations lead to mutually parallel and perpendicular alignments, respectively. At an incident intensity of 10 mW/µm2, the rotational potential depths are more than 30 times as large as the Brownian motion energy, enabling the optical alignments with angle fluctuations less than ∼±10°. Thus, this optical alignment of the nanoparticles with the plasmon coupling allows dynamic control of the plasmonic characteristics and functions.

Metal-catalyzed alkyne oxidation/CH functionalization: Effects of oxidant, temperature, and metal catalyst on chemoselectivity.

Gold-catalyzed intermolecular alkyne oxidation has attracted much synthetic attention, but mostly suffering undesired over-oxidation. Recent experiments demonstrated that over-oxidation could be dramatically suppressed in zinc(II)-catalyzed intermolecular alkyne oxidation/CH functionalization. By means of first-principle density functional theory calculations, we explored the mechanism of the M-catalyzed intermolecular alkyne oxidations (M = Zn(OTf)2 and Au+ PR3 ) as well as the effects of oxidants, temperature, and metal catalysts on chemoselectivity, in an effort to disclose the origin of the extraordinary chemoselectivity pertaining to zinc catalysis. Our calculations indicate that the Zn-catalyzed intermolecular alkyne oxidation/CH functionalization proceeds by a Friedel-Crafts alkylation mechanism rather than metal carbene insertion mechanism. The chemoselectivity of CH functionalization against over-oxidation in Zn catalysis, in comparison with gold catalysis, can be jointly controlled by four factors: (1) the use of less nucleophilic N-oxide, (2) the enhanced electrophilicity and carbocationic nature of the carbenic site in the α-oxo metal carbenoid intermediate, (3) enhanced steric repulsion to incoming oxidant exerted by bulky ancillary ligand in the close nearby of the carbenic site to disfavor intermolecular over-oxidation and (4) the large negative value of activation entropy in the intermolecular over-oxidation pathway, that jointly give rise to lower activation free energy for the intramolecular cyclization/CH functionalization pathway than for the intermolecular over-oxidation pathway. © 2018 Wiley Periodicals, Inc.

Volume holographic recording in Al nanoparticles dispersed phenanthrenequinone-doped poly(methyl methacrylate) photopolymer.

High-performance material plays a crucial role in holographic data storage, which is a noteworthy technology with potential applications in the field of high capacity data storage. We report on a new kind of holographic storage material based on aluminum nanoparticles (Al NPs) dispersed phenanthrenequinone-doped poly(methyl methacrylate) (PQ/PMMA) photopolymer. Al NPs are efficiently synthesized in a monomer solvent using laser ablation in liquids without chemical precursors. It is shown that an increase in diffraction efficiency and recording sensitivity is achieved in both traditional holography and polarization holography by doping with Al NPs. After 4 h of ablation, the new material exhibited an improvement in the diffraction efficiency for both traditional holography and polarization holography from 2.85% to 57.15% and from 0.6% to 4.07%, respectively. We also investigated the image recording and reconstruction performance for both traditional and polarization holography and the results indicate that the proposed material has noticeable potential as a holographic storage material. Additionally, it also possesses excellent potential for holographic position multiplexing recording. We conclude that laser ablation in a liquid is a promising option for processing low-cost nano-doped holographic storage material.

Improving the polarization-holography performance of PQ/PMMA photopolymer by doping with THMFA.

Increasing photosensitizer concentration has been considered as an effective approach to improve the performance of holographic material. In this paper, we report on new method for increasing the saturated dissolvability of photosensitizer PQ within polymeric media by introducing copolymerization monomer into the PQ/PMMA. The photosensitizer concentration of PQ was increased from 0.7wt% to 1.3wt%, compared with the typical PQ/PMMA sample. Besides, we investigated performance of polarization holographic recordings in typical PQ/PMMA and copolymerization monomer-containing PQ/PMMA with the orthogonally polarized signal and reference waves. And the doping of THFMA component resulted in a significant improvement of diffraction intensity and photosensitivity. In addition, high-quality holographic image reconstruction was realized in our home-made material.

Dual-channel recording based on the null reconstruction effect of orthogonal linear polarization holography.

We report on dual-channel recording within polarization holography written by orthogonal linear polarization waves. The null reconstruction effect (NRE) of linear polarization holography was experimentally achieved at a large cross-angle of π/2 inside the polarization-sensitive media. Based on the NRE, two polarization encoded holograms were recorded in a dual-channel recording system with negligible inter-channel crosstalk. The two polarization multiplexed holograms could then be sequentially or simultaneously readout by shifting the polarization state of reference wave with the best signal-to-noise of 18:1 obtained within the experiment.

Null reconstruction of orthogonal circular polarization hologram with large recording angle.

We report on the null reconstruction of polarization volume hologram recorded by orthogonal circularly polarized waves with a large cross angle. Based on the recently developed tensor theory for polarization holography, the disappearance of the reconstruction was analytically verified, where a nice agreement was found between the experimental and theoretical results. When the polarization and intensity hologram attain a balance, not only the null reconstruction but also the faithful reconstruction can be realized by the illumination of the orthogonal reference wave and original reference wave. As a consequence of the hologram recorded without paraxial approximation, the null reconstruction may lead to important applications, such as a potential enhancement in optical storage capacity for volume holograms.

Aspertetranones A-D, Putative Meroterpenoids from the Marine Algal-Associated Fungus Aspergillus sp. ZL0-1b14.

Aspertetranones A-D (1-4), four new highly oxygenated putative rearranged triketide-sesquiterpenoid meroterpenes, were isolated from the marine algal-associated fungus Aspergillus sp. ZL0-1b14. On the basis of a comprehensive spectroscopic analysis, the planar structures of aspertetranones were determined to possess an unusual skeleton in the terpenoid part. The relative and absolute configurations of the aspertetranones were assigned on the basis of NOESY analysis, X-ray crystallography, and circular dichroism spectroscopy. Compounds 1-4 were evaluated for anti-inflammatory activity in LPS-stimulated RAW264.7 macrophages. Aspertetranone D exhibited an inhibitory effect against IL-6 production with 69% inhibition at 40 µM.

Two new spirooxindole alkaloids from rhizosphere strain Streptomyces sp. xzqh-9.

Two new spirooxindole alkaloids spindomycins A (1) and B (2) were isolated from rhizosphere strain Streptomyces sp. xzqh-9. Their structures were elucidated by comprehensive spectroscopic analyses of NMR and MS data. The absolute configurations of 1 and 2 were determined by experimental and theoretical calculation of electronic circular dichroism (ECD). Antitumor, lactate dehydrogenase, and tyrosine kinase inhibitory activities of two compounds were evaluated, while only spindomycin B (2) exhibited weak inhibitory activity against tyrosine kinase Bcr-Abl.

Highly enantioselective Henry reactions of aromatic aldehydes catalyzed by an amino alcohol-copper(II) complex.

Amino alcohol-Cu(II) catalyst: Highly enantioselective Henry reactions between aromatic aldehydes and nitromethane have been developed. The reactions were catalyzed by an easily available and operationally simple amino alcohol-copper(II) catalyst. In total, 38 substrates were tested and the R-configured products were obtained in good yields with excellent enantioselectivities.

Biosynthesis and Chemical Diversification of Verucopeptin Leads to Structural and Functional Versatility.

A synthesis program for structurally complex macrocycles is very challenging. Herein, we propose a biosynthesis pathway of the pyranylated cyclodepsipeptide verucopeptin to make enough supply and to diversify verucopeptin by genetic manipulation and one-step semisynthesis. The synthesis relies on the intrinsic reactivity of the interchangeable hemiketal pyrane and opened keto along with adjacent alkene. Biological evaluation of verucopeptin-oriented analogs delivers a potent AMP-activated protein kinase (AMPK) agonist, antibacterial agent, and selective NFκB modulator.

Pharmacological Targeting of Vacuolar H+-ATPase via Subunit V1G Combats Multidrug-Resistant Cancer.

Multidrug resistance (MDR) in cancer remains a major challenge for the success of chemotherapy. Natural products have been a rich source for the discovery of drugs against MDR cancers. Here, we applied high-throughput cytotoxicity screening of an in-house natural product library against MDR SGC7901/VCR cells and identified that the cyclodepsipeptide verucopeptin demonstrated notable antitumor potency. Cytological profiling combined with click chemistry-based proteomics revealed that ATP6V1G directly interacted with verucopeptin. ATP6V1G, a subunit of the vacuolar H+-ATPase (v-ATPase) that has not been previously targeted, was essential for SGC7901/VCR cell growth. Verucopeptin exhibited strong inhibition of both v-ATPase activity and mTORC1 signaling, leading to substantial pharmacological efficacy against SGC7901/VCR cell proliferation and tumor growth in vivo. Our results demonstrate that targeting v-ATPase via its V1G subunit constitutes a unique approach for modulating v-ATPase and mTORC1 signaling with great potential for the development of therapeutics against MDR cancers.

New 12,8-Eudesmanolides from Eutypella sp. 1-15.

Four new 12,8-Eudesmanolides (1-4) and one known compound 5 named 13-Hydroxy-3,7(11)-eudesmadien-12,8-olide, were isolated from a mangrove rhizosphere-derived fungus Eutypella sp. 1-15. Their structures with absolute stereochemistry were determined by the comprehensive spectroscopic data, experimental and calculated ECD analysis. Compound 1 exhibited potent anticancer activity against JEKO-1 and HepG2 with IC50 values of 8.4 and 28.5 µM, respectively. Additionally, compound 1 also showed moderate antimicrobial activity.