Peptide sequence mediated self-assembly of molybdenum blue nanowheel superstructures

The precise control over the formation of complex nanostructures, e.g. polyoxometalates (POMs), at the sub-nanoscale is challenging but critical if non-covalent architectures are to be designed. Combining biologically-evolved systems with inorganic nanostructures could lead to sequence-mediated assembly. Herein, we exploit oligopeptides as multidentate structure-directing ligands via metal-coordination and hydrogen bonded interactions to modulate the self-assembly of POM superstructures. Six oligopeptides (GH, AH, SH, G₂H, G₄H and G₅H) are incorporated into the cavities of Molybdenum Blue (MB) POM nanowheels. It is found that the helicity of the nanowheel can be readily switched (Δ to Λ) by simply altering the N-terminal amino acid on the peptide chain rather than their overall stereochemistry. We also reveal a delicate balance between the Mo-coordination and the hydrogen bonds found within the internal cavity of the inorganic nanowheels which results in the sequence mediated formation of two unprecedented asymmetrical nanowheel frameworks: {Mo₁₂₂Ce₅} and {Mo₁₂₆Ce₄}.

Peptide sequence can be used to control the self-assembly and structures of nanoscale molybdenum blue polyoxometalate (POM) wheel-shaped clusters.     

Nickel and potassium co-modified β-Mo2C catalyst for CO conversion

Nickel and potassium co-medified β-Mo2C catalysts were prepared and used for CO hydrogenation reaction. The major products over β-Mo2C were C1-C4 hydrocarbons, only few alcohols were obtained. Addition of potassium resulted in remarkable selectivity shift from hydrocarbons to alcohols at the expense of CO conversion over β-Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation with a higher C2+OH production. Modified by nickel, β-Mo-2C showed a relatively high CO conversion, however, the products were similar to those of pure β-Mo2C. When co-modified by nickel and potassium,β-Mo2C exhibited high activity and selectivity towards mixed alcohols synthesis, and also the whole chain propagation to produce alcohols especially for the stage of C1OH to C2OH was remarkably enhanced. It was concluded that the Ni and K had, to some extent, synergistic effect on CO conversion.     

Two new benzaldehyde derivatives from mangrove endophytic fungus (No. ZZF 32)

Two new benzaldehyde derivatives, 6-ethyl-2-hydroxy-4-methoxy-3-methylbenzaldehyde (1), 6-ethyl-2,4-dihydroxy-3-methylbenzaldehyde (2), together with 2, 4-dihydroxy-3,6-dimethylbenzaldehyde (3) were isolated from mangrove fungus (No. ZZF 32#) from the South China Sea. The structures of compounds 1 and 2 were established by comprehensive analysis of the spectral data, especially 2D NMR spectral results.     

Structure elucidation of three diphenyl ether derivatives from the mangrove endophytic fungus SBE‐14 from the South China Sea

Two new natural products, tenelate A ( 1 ) and B ( 2 ), together with the known compound, tenellic acid C ( 3 ), were isolated from the mangrove endophytic fungus Talaromyces sp. (SBE‐14), from the South China Sea. Their structures were elucidated by spectroscopic methods, mainly 1D and 2D NMR techniques. Copyright © 2009 John Wiley & Sons, Ltd.     

All-silicon chiral metasurfaces and wavefront shaping assisted by interference

The usage of full-color imaging in digital pathology produces significant results. Compared with a grayscale image or a pseudocolor image containing contrast information, a full-color image can identify and detect the target object better with color texture information. Fourier ptychographic microscopy(FPM) is a high-throughput computational imaging technique that breaks the tradeoff between high resolution(HR) and a large field of view. It also eliminates the artifacts of scanning and stitching in digital pathology and improves its imaging efficiency. However, the conventional full-color digital pathology based on FPM is still time-consuming because of the repeated experiments with tri-wavelengths. A color transfer FPM approach termed "CFPM" was reported. The color texture information of a low-resolution full-color pathologic image is directly transferred to the HR grayscale FPM image captured by only a single wavelength. Both of the color space of FPM based on the standard CIE-XYZ color model and the display based on the standard RGB color space were established. Different FPM colorization schemes were analyzed and compared with 30 biological samples. Three types of evaluation approaches were provided, including the root-mean-square error(RMSE), the difference maps, and the image histogram cosine similarity. The average RMSE values of the conventional method and CFPM compared with the ground truth were 5.3% and 5.7%, respectively. Therefore, the reconstruction time is significantly reduced by 2/3 with the sacrifice of precision of only 0.4%. The CFPM method is also compatible with advanced fast FPM approaches to further reduce computation time.     

XPS study of potassium-promoted molybdenum carbides for mixed alcohols synthesis via CO hydrogenation

The X-ray photoelectron spectroscopy (XPS) was used to investigate the surface characteristic of potassium-promoted or un-promoted both β-Mo_2C and α-MoC_(1-x) pretreated by syngas at different temperatures, and the promotional effect of potassium on the catalytic performance was also studied. XPS results revealed that the content of surface Mo and its valence distribution between β-Mo_2C and α-MoC_(1-x) were quite different. Promoted by potassium, the remarkable changes were observed for surface composition and valence of Mo distribution over β-Mo_2C. Potassium had strong electronic effect on β-Mo_2C, which led to a higher Mo~(4+) content. On the contrary, potassium had little electronic effect on α-MoC_(1-x), and K-Mo interaction was weak. Therefore, Mo~0 and Mo~(2+) became the dominant species on the catalyst surface, and the Mo~(4+) content showed almost no increase as the pretreatment temperature enhanced. In terms of catalytic performance of molybdenum carbides, the increase in Mo~0 most likely explained the increase in hydrocarbon selectivity, yet Mo~(4+) might be responsible for the alcohols synthesis.     

A new griseofulvin derivative from the mangrove endophytic fungus <Emphasis Type="Italic">Sporothrix</Emphasis> SP.

A new griseofulvin derivative, 7-chloro-2',5,6-trimethoxy-6'-methylspiro(benzofuran-2(3H),1'-(2) cyclohexene)3,4'-dione (1), together with the known 2-acetyl-7-methoxybenzofuran (2), was isolated from the marine-derived mangrove endophytic fungus Sporothrix sp. (No. 4335). The structure of new compound 1 was elucidated by analysis of spectroscopic data.     

Structure,biological and electrochemical studies of transition metal complexes from N,S,N′ donor ligand 8-(2-pyridinylmethylthio)quinoline

The semirigid tridentate 8-(2-pyridinylmethylthio)quinoline ligand (Q1) is shown to form the structurally characterized transition metal complexes [Cu(Q1)Cl₂] (1), [Co(Q1)(NO₃)₂] (2), [Cd(Q1)(NO₃)₂] (3), [Cd(Q1)I₂] (4). [Cu(Q1)₂](BF₄)₂·(H₂O)₂ (5), [Cu(Q1)₂](ClO₄)₂·(CH₃COCH₃)₂ (6), [Zn(Q1)₂](ClO₄)₂(H₂O)₂ (7), [Cd₂(Q1)₂Br₄] (8), [Ag₂(Q1)₂(ClO₄)₂] (9), and [Ag₂(Q1)₂(NO₃)₂] (10). Four types of structures have been observed: ML-type in complexes 1–4, in which the anions Cl⁻, NO₃⁻ or I⁻ also participate in the coordination; ML₂⁻ type in complexes 5–7 without direct coordination of the anions BF₄⁻ or ClO₄⁻ and with more (Cu²⁺) or less (Zn²⁺) distorted bis-fac coordinated Q1; M₂L₂-type in complex 8, in which two Br⁻ ions act as bridges between two metal ions; and M₂(μ-L)₂-type in complexes 9 and 10, in which the ligand bridges two anion binding and Ag–Ag bonded ions. Depending on electron configuration and size, different coordination patterns are observed with the bonds from the metal ions to N_pyridyl longer or shorter than those to N_quinoline. Typically Q1 acts as a facially coordinating tridentate chelate ligand except for the compounds 9 and 10 with low-coordinate silver(I). Except for 6 and 8, the complexes exhibit distinct constraining effects against both G(+) and G(-) bacteria. Complexes 1, 3, 4, 5, 7 have considerable antifungal activities and complexes 1, 5, 7, and 10 show selective effects to restrain certain botanic bacteria. Electrochemical studies show quasi-reversible reduction behavior for the copper(II) complexes 1, 5 and 6.     

Wave-coupling theory of linear electro-optic effect for ultrashort laser pulses

A wave-coupling theory of linear electro-optic (EO) effect for ultrashort laser pulses has been developed. As one of its applications, the linear EO effect of ultrashort Gaussian pulses propagating in LiNbO₃ crystal is demonstrated, with the intensity lower than the damage threshold. It is found that the EO effect is sensitive to both the azimuth angle and the polar angle of wave vector of light. And the larger the applied electric field, the shorter the crystal used for optimization of EO coupling is. The numerical results show that, with the duration of input pulse changing from 150 fs to 5 fs, the durations of output pulses are broadened due to the group-velocity dispersion, as well as the first- and second-order refractive dispersion. In addition, when input pulse duration is larger than 20 fs, in contrast with zero chirp, the output durations can be slightly compressed if a positive chirp input pulse is used. The validities of slowly varying amplitude approximation and continuous wave approximation are also discussed. The influence of self-phase modulation and cross-phase modulation on the EO effect is also discussed briefly.     

计及两体和三体作用下的二维凝聚体中的孤子特性

使用多重尺度法,解析地研究计及粒子间两体和三体同时作用下二维凝聚体中孤子的特性. 结果发现,当凝聚体粒子间两体作用为排斥、三体作用为吸引时,凝聚体内会产生暗孤子环,且随着三体吸引作用的减弱,暗孤子环中心峰的高度逐渐降低,并当三体吸引作用消失时暗孤子环演化为一个完美的二维暗孤子. 当两体和三体作用均为排斥时,凝聚体中的暗孤子的宽度和幅度随着三体排斥作用的加强而减小,且当三体作用强度增加到与两体作用同一数量级时,凝聚体产生坍塌现象. 关键词： 玻色-爱因斯坦凝聚体 两体和三体作用 暗孤子