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981.
Liang Wang Jun Yue Bai Peng Fei Huang Hong Jing Wang Xiao Wei Wu Yu Qing Zhao 《Mikrochimica acta》2007,158(1-2):73-78
The electrochemical behaviors of uric acid (UA) at the penicillamine (Pen) self-assembled monolayers modified gold electrode
(Pen/Au) have been studied. The Pen/Au electrode is demonstrated to promote the electrochemical response of UA by cyclic voltammetry
(CV). The diffusion coefficient D of UA is 6.97 × 10−6 cm2 s−1. In differential pulse voltammetric (DPV) measurements, the Pen/Au electrode can separate the UA and ascorbic acid (AA) oxidation
potentials by about 120 mV and can be used for the selective determination of UA in the presence of AA. The detection limit
was 1 × 10−6 mol L−1. The modified electrode shows excellent sensitivity, good selectivity and antifouling properties. 相似文献
982.
Erin J. Peterson Wei Qi Ian N. Stanton Peng Zhang Michael J. Therien 《Chemical science》2020,11(31):8095
High quantum yield NIR fluorophores are rare. Factors that drive low emission quantum yields at long wavelength include the facts that radiative rate constants increase proportional to the cube of the emission energy, while nonradiative rate constants increase in an approximately exponentially with decreasing S0–S1 energy gaps (in accordance with the energy gap law). This work demonstrates how the proquinoidal BTD building blocks can be utilized to minimize the extent of excited-state structural relaxation relative to the ground-state conformation in highly conjugated porphyrin oligomers, and shows that 4-ethynylbenzo[c][1,2,5]thiadiazole (E-BTD) units that terminate meso-to-meso ethyne-bridged (porphinato)zinc (PZnn) arrays, and 4,7-diethynylbenzo[c][1,2,5]thiadiazole (E-BTD-E) spacers that are integrated into the backbone of these compositions, elucidate new classes of impressive NIR fluorophores. We report the syntheses, electronic structural properties, and emissive characteristics of neoteric PZn-(BTD-PZn)n, PZn2-(BTD-PZn2)n, and BTD-PZnn-BTD fluorophores. Absolute fluorescence quantum yield (ϕf) measurements, acquired using a calibrated integrating-sphere-based measurement system, demonstrate that these supermolecules display extraordinary ϕf values that range from 10–25% in THF solvent, and between 28–36% in toluene solvent over the 700–900 nm window of the NIR. These studies underscore how the regulation of proquinoidal conjugation motifs can be exploited to drive excited-state dynamical properties important for high quantum yield long-wavelength fluorescence emission.Incorporation of proquinoidal BTD building blocks into conjugated porphyrin oligomers minimizes the extent of excited-state structural relaxation relative to the ground-state conformation, elucidating new classes of impressive NIR fluorophores. 相似文献
983.
Yi XY Liu B Jiménez-Aparicio R Urbanos FA Gao S Xu W Chen JS Song Y Zheng LM 《Inorganic chemistry》2005,44(12):4309-4314
Four mixed-valent ruthenium diphosphonates, namely, Na(4)[Ru(2)(hedp)(2)X]x16H(2)O [X = Cl (1), Br (2)], K(3)[Ru(2)(hedp)(2)(H(2)O)(2)]x6H(2)O (3), and Na(7)[Ru(2)(hedp)(2)Fe(CN)(6)]x24H(2)O (4), where hedp represents 1-hydroxyethylidenediphosphonate [CH(3)C(OH)(PO(3))(2)](4-), were synthesized and structurally characterized. Compounds 1, 2, and 4 show linear chain structures in which the mixed-valent [Ru(2)(hedp)(2)](3-) dimers are linked by X(-) or [Fe(CN)(6)](4-) bridges. Compound 3 contains discrete species of [Ru(2)(hedp)(2)(H(2)O)(2)](3-) where the axial positions of [Ru(2)(hedp)(2)](3-) paddlewheel are terminated by water molecules. Magnetic studies show that significant antiferromagnetic exchanges are mediated between the [Ru(2)(hedp)(2)](3-) (S = 3/2) units through halide bridges in compounds 1 and 2. 相似文献
984.
Yang M Wang W Yuan F Zhang X Li J Liang F He B Minch B Wegner G 《Journal of the American Chemical Society》2005,127(43):15107-15111
The synthesis of a block codendrimer (g3-PBE-b-g3-PMDC), composed of a third-generation poly(benzyl ether) (PBE) monodendron and an aliphatic polyether (PMDC) monodendron is reported. In THF/diiospropyl ether (1:1) the PMDC block functions as a "hydrophilic" block, while the PBE acts as a "hydrophobic" block. The codendrimer can form interdigitated layers leading to vesicle formation. Tapping mode atomic force microscopy (AFM), dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to characterize the vesicles. The effect of molecular architecture on the formation of the interdigitated layers and vesicles was studied. 相似文献
985.
Ai‐Hua Zhao Yan Zhang Zhao‐Hui Xu Jian‐Wen Liu Wei Jia 《Helvetica chimica acta》2004,87(12):3160-3166
Three new enmein‐type ent‐kaurenoids, i.e., the two pairs 1 and 2 of 20‐epimers and the (20R)‐isomer 3 , besides the seven known diterpenoids 4 – 10 , were isolated from the aerial parts of Isodon serra. Their structures were elucidated by spectroscopic techniques and X‐ray diffraction. The immunosuppressive effect for T‐lymphocytes proliferation induced by Con A in BALB/c mouse was evaluated for the isolates 1 – 10 . They all displayed a remarkable inhibitory effect, with multi‐glycosides of Tripterygium wilfordii as positive reference substance (Table 3). 相似文献
986.
Alexandra Alimova A. Katz Rakhi Podder Glenn Minko Hul Wei R. R. Alfano Paul Gottlieb 《Photochemistry and photobiology》2004,80(1):41-46
Native fluorescence spectroscopy was used for in situ investigations of two lipid‐containing bacteriophages from the cystovirus family as well as their Pseudomonad host cells. Both the viruses φ6 and φ12 and their bacterial host proteins contain the amino acid tryptophan (trp), which is the predominant fluorophore in UV. Within proteins, trp's structural environment differs, and the differences are reflected in their spectroscopic signatures. It was observed that the peak of the trp emission from both viruses was at 330 nm, a significantly shorter wavelength than trp in either the Pseudomonad host cells or the amino acid's chemical form. This allowed us to monitor the viral attachment process and subsequent lytic release of progeny virus particles by measurement of the trp emission spectra during the infection process. This work demonstrates that fluorescence may offer a novel tool to detect viruses and monitor viral infection of cells and may be part of a biodefense application. 相似文献
987.
Ming‐Liang Tong Wei Li Xiao‐Ming Chen Shao‐Liang Zheng Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):m232-m234
The title compound, [Cu2(C2H3O2)4(C11H9N)2] or [Cu2(MeCO2)4(phpy)2] (phpy is 4‐phenylpyridine), consists of centrosymmetric dimers in which the CuII atoms display a square‐pyramidal CuO4N coordination, with four acetate O atoms in the basal plane [Cu—O 1.975 (3)–1.987 (3) Å] and the phpy N atom in the apical position [Cu—N 2.150 (3) Å]. The Cu atoms are 2.654 (1) Å apart and are bridged by four acetate groups. The discrete dimers are extended into a three‐dimensional supramolecular array through intermolecular π–π‐stacking interactions. 相似文献
988.
Wei F Chen C Zhai L Zhang N Zhao XS 《Journal of the American Chemical Society》2005,127(15):5306-5307
Conventional single nucleotide polymorphism (SNP) assays, which based their detection on the stringency or temperature of the washing buffers, have encountered difficulties to distinguish a single base pair mismatch from a perfect match. In this study, scanning potential hairpin denaturation (SPHD) has been developed to detect SNP in a sensitive and reliable manner. Combined with hairpin oligonucleotide probes, scanning surface electric potential was used to induce a dissociation of double-stranded DNA around a unique "melting potential" (Vm), and it generated a high-contrast SNP recognition signal. A 21 base pair p53 gene segment was used to test this novel method. A single nucleotide mismatch to the hairpin probes caused an average of 400-800 mV difference in melting potential against the perfect match, while the error of this assay was lower than 20 mV. Experiments demonstrated that the hairpin stem was critical to the method. The concept of scanning potential hairpin denaturation could also be used extensively in different areas of nucleotide hybridization based assays. 相似文献
989.
A highly general, convenient, and inexpensive catalyst system was developed for the N-arylation of sulfonamides with aryl iodides or bromides by using 5-20 mol % of CuI as catalyst, 20 mol % of N-methylglycine (for aryl iodides) or N,N-dimethylglycine (for aryl bromides) as ligand, and K3PO4 as base. 相似文献
990.
Hai‐Yang Liu Shi‐Jin Li Yi Zhao Wei Ni Xiao‐Jiang Hao Jun‐Zhu Li Yan Hua Bai‐Bo Xie Chen Qing Chang‐Xiang Chen 《Helvetica chimica acta》2007,90(10):2017-2023
Four new podocarpane‐type trinorditerpenenes, (5β,10α)‐12,13‐dihydroxypodocarpa‐8,11,13‐trien‐3‐one ( 1 ), (5β,10α)‐12‐hydroxy‐13‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 2 ), (5β,10α)‐13‐hydroxy‐12‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 3 ), and (3α,5β,10α)‐13‐methoxypodocarpa‐8,11,13‐triene‐3,12‐diol ( 4 ), together with four known diterpenes, 12‐hydroxy‐13‐methylpodocarpa‐8,11,13‐trien‐3‐one ( 5 ), spruceanol ( 6 ), ent‐3α‐hydroxypimara‐8(14),15‐dien‐12‐one ( 7 ), and ent‐3β,14α‐hydroxypimara‐7,9(11),15‐triene‐12‐one ( 8 ), were isolated from the twigs and leaves of Aleurites moluccana. Their structures were elucidated by means of comprehensive spectroscopic analyses, including NMR and MS. Except 8 , all compounds were evaluated for their cytotoxicity; compound 4 exhibited moderate inhibitory activity against Raji cells with an IC50 value of 4.24 μg/ml. 相似文献