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991.
The chemical bonding and spectral assignments of rhodium(III)‐catalyzed closo‐dodecaborate complexes: Ab initio study 下载免费PDF全文
Xiaojun Li Xiaohui Yang Hongjiang Ren Ping Sun Zhenhua Fang 《International journal of quantum chemistry》2017,117(19)
The chemical bonding and spectral assignments of rhodium(III)‐catalyzed closo‐dodecaborate (RhCD) complex are systematically studied using the density functional theory calculations. It is found that the calculated main bond lengths of framework are in good agreement with experimental X‐ray observation, and the pronounced hybridization of B‐2p and Rh‐4d states is responsible for the structural stability, reflected by the large dissociation energy and HOMO–LUMO energy gap. The AdNDP chemical bonding analysis indicates that the RhCD complex can be stabilized by two H‐bridged 3c‐2e σ‐bonds (B‐H‐Rh triangles). Additionally, the theoretical calculations reproduce well the main experimental IR spectrum, and the characteristic peaks are properly assigned. These results will be helpful for further insight into the unique electronic structure of the species, and provide valuable references for potential applications in novel materials. 相似文献
992.
Crystal Structures of Bacterial (6‐4) Photolyase Mutants with Impaired DNA Repair Activity 下载免费PDF全文
Kalinga Bowatte Dennis Kwiatkowski Esther Mittmann Heba Qasem Norbert Krauß Xiaoli Zeng Zhong Ren Patrick Scheerer Xiaojing Yang Tilman Lamparter 《Photochemistry and photobiology》2017,93(1):304-314
PhrB from Agrobacterium fabrum is the first prokaryotic photolyase which repairs (6‐4) UV DNA photoproducts. The protein harbors three cofactors: the enzymatically active FAD chromophore, a second chromophore, 6,7‐dimethyl‐8‐ribityllumazine (DMRL) and a cubane‐type Fe‐S cluster. Tyr424 of PhrB is part of the DNA‐binding site and could provide an electron link to the Fe‐S cluster. The PhrBY424F mutant showed reduced binding of lesion DNA and loss of DNA repair. The mutant PhrBI51W is characterized by the loss of the DMRL chromophore, reduced photoreduction and reduced DNA repair capacity. We have determined the crystal structures of both mutants and found that both mutations only affect local protein environments, whereas the overall fold remained unchanged. The crystal structure of PhrBY424F revealed a water network extending to His366, which are part of the lesion‐binding site. The crystal structure of PhrBI51W shows how the bulky Trp leads to structural rearrangements in the DMRL chromophore pocket. Spectral characterizations of PhrBI51W suggest that DMRL serves as an antenna chromophore for photoreduction and DNA repair in the wild type. The energy transfer from DMRL to FAD could represent a phylogenetically ancient process. 相似文献
993.
Lin-Yan Xu Chun-Yu Liu Shi-Yuan Liu Zhi-Gang Ren David James Young Jian-Ping Lang 《Tetrahedron》2017,73(22):3125-3132
One palladium dichloride adduct of a phosphine-pyridine ligand N-diphenylphosphanyl-2-aminopyridine (L1) [(L1)PdCl2] (1) has been prepared and structurally characterized. Compound 1 can be used as an effective catalyst for the Suzuki-Miyaura cross-coupling reactions of unreactive aryl chlorides with aryl boronic acids, and worked much better than its mono- or bidentate phosphine ligands. The reactions with a wide scope of substrates proceeded to give desired products in good to excellent yields. 相似文献
994.
A new dual chemosensor (TTF-PBA) for Fe3+ and Cu2+ in different signal pathways was designed and synthesized. The absorption spectrum, fluorescence spectrum and cyclic voltammograms changed in the presence of Cu2+ and Fe3+. The optical color changed within 5 s from yellow to orange upon the addition of Cu2+, and it changed to dark yellow when Fe3+ existed. The cyclic voltammogram of Cu2+/TTF-PBA changed from Eox = 0.50 V, Ered = 0.32 V to Eox = 0.64 V, Ered = 0.80 V (vs Ag/AgCl) upon the addition of 2.0 equiv. Cu2+. As for Fe3+/TTF-PBA, its oxidation wave disappeared, and its reduction wave appeared at Ered = ?0.59 V (vs Ag/AgCl) upon the addition of 4.0 equv. Fe3+. The sensor displayed high selectivity for Cu2+ and Fe3+ over other ions including Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+ and Au3+, the detection limits for Cu2+ and Fe3+ ion reached as low as 5.33 × 10?7 mol/L and 5.34 × 10?7 mol/L, respectively. Furthermore, when Fe3+ existed, Cu2+ can be detected sequentially by the sensor through the absorption spectrum and the color change observed by naked-eyes. 相似文献
995.
Jie Ren Chao Fan Yi-Gong Guo Shi-Kai Yan Richard D. Ye Yan Zhang Hui-Zi Jin Wei-Dong Zhang 《Tetrahedron》2017,73(12):1611-1617
A phytochemical investigation of the whole plant of Liparis regnieri Finet led to the isolation of one new biphenantherene (1) and ten new nervogenic acid derivatives (2–11), together with nine known compounds. Their structures were elucidated mainly by extensive analyses of 1D and 2D NMR spectroscopic data and chemical reactions. Additionally, for the first time a previously unreported biphenantherene was discovered to effectively suppress TNF-α induced expression of NF-κB-Luc in Hela cells with the IC50 value of 1.80 μM and the structure-activity relationshipwas also discussed. 相似文献
996.
997.
998.
Wei Cheng Ming Ji Xiaodan Li Jinwei Ren Fuling Yin Leen van Ofwegen Siwang Yu Xiaoguang Chen Wenhan Lin 《Tetrahedron》2017,73(17):2518-2528
Chemical investigation of the gorgonian coral Junceella fragilis resulted in the isolation of a new norditerpenoid fragilolide A (1), sixteen new briarane diterpenoids fragilolides B-Q (2–17), together with frajunolides H and N, and three known norcembranoids scabrolide D, sinuleptolide and 5-epi-sinuleptolide. The structures of new compounds were determined on the basis of extensive spectroscopic analysis, including the experimental and calculated ECD data and single-crystal X-ray diffraction for the configurational assignments. The structure of fragilolide A featured an unprecedented 4,13- and 7,11-fused tetracyclic norcembranoid, while the biogenetic relationships of the briarane analogues were postulated. Frajunolide H exerted significant inhibition against a panel of tumor cell lines, and six briarane diterpenoids (3, 6, 8, 12, 16, and frajunolide N) exhibited the inhibitory effects against the HBeAg express of hepatitis B virus in HepAD38 cells. In addition, sinuleptolide and 5-epi-sinuleptolide exerted the effects to inhibit NO production in RAW264.7 macrophage cells, in addition to the activation of ARE and the inhibition of NF-κB expression. 相似文献
999.
Xuan Ma Xu-Hua Nong Zhe Ren Jie Wang Xiao Liang Lu Wang Shu-Hua Qi 《Tetrahedron letters》2017,58(12):1151-1155
A new cyclic pentapeptide and three new linear peptides, namely, aspergillipeptides D–G (1–4), were isolated from a culture broth of marine gorgonian-derived fungus Aspergillus sp. SCSIO 41501. Their structures were elucidated by spectroscopic analysis, and their absolute configurations were confirmed by Marfey’s method. Compounds 1 and 2 showed evident antiviral activity against herpes simplex virus type 1 (HSV-1) with IC50 values of 9.5 and 19.8 µM under their non-cytotoxic concentrations against a Vero cell line, respectively, and 1 also had antiviral activity against acyclovir-resistant clinical isolates of HSV-1. 相似文献
1000.
A highly selective HBT-based “turn-on” fluorescent probe for hydrazine detection and its application
Zhen Chen Xinxin Zhong Wangbo Qu Ting Shi Heng Liu Hanping He Xiuhua Zhang Shengfu Wang 《Tetrahedron letters》2017,58(26):2596-2601
As one of the important industrial chemicals, hydrazine (N2H4) can be inhaled through the skin, leading to many serious health issues. In this paper, we constructed a novel turn-on fluorescent probe HBTM for N2H4 detection based on ESIPT and ICT mechanism by incorporating the methyl dicyanvinyl group to 2-(2′-hydroxylphenyl) benzothiazole (HBT) fluorophore. The probe showed the following advantages: high sensitivity with detection limit of 2.9 × 10?7 M, high selectivity over other related interfering species, wide linear range of 0–140 μM and pH value adaptation. Moreover, the probe could detect N2H4 on paper strips and image N2H4 in living cells. 相似文献