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991.
A series of six new, highly soluble N,N'-dialkylated isoindigo derivatives bearing different electron donating thiophene units at the 6,6'-positions were synthesized by Stille cross-coupling reaction. The optical and electrochemical properties of these dyes were studied by UV-vis spectroscopy and cyclic voltammetry, revealing a good tunability of their electronic properties by peripheral substituents with amino groups leading to strong absorption reaching the NIR region. The DFT calculations of the frontier molecular orbitals of these dyes corroborate the observed substituent effect on absorption and redox properties. 相似文献
992.
Goldstein DC Cheng YY Schmidt TW Bhadbhade M Thordarson P 《Dalton transactions (Cambridge, England : 2003)》2011,40(9):2053-2061
Four new hetero- and homo-leptic iridium(III) bisterpyridine complexes have been prepared which incorporate aniline (tpy-φ-NH(2)), benzoic acid (tpy-φ-COOH), and benzyl alcohol (tpy-φ-CH(2)OH) substituents at the 4' positions of the tpy ligands (tpy = 2,2':6',2'-terpyridine, φ = phenylene). The electrochemical behaviour and ground and excited state spectroscopic properties of the complexes are reported, and the X-ray crystal structures of a homoleptic benzyl alcohol [Ir(tpy-φ-CH(2)OH)(2)](PF(6))(3), homoleptic aniline [Ir(tpy-φ-NH(2))(2)](PF(6))(3), and heteroleptic benzyl alcohol/aniline substituted complex [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))](PF(6))(3) have been solved. Complexes with aniline substituents were found to display absorption bands at around 430 nm corresponding to intraligand charge transfer (ILCT) that are sensitive to changes in solvent and pH. Strong emission in the visible region involving the ILCT state is observed in two of the complexes (Φ(e) = 0.7% and 2.6%) in acetonitrile. In the heteroleptic aniline/benzyl alcohol complex the Stokes shift is shown to be linearly related to solvent polarisability according to the Lippert equation, but only for solvents with weak hydrogen bonding interactions. Additionally, in water, emission from the ILCT state is quenched and only weak ligand centred (LC) emission is observed. The long lifetimes and quantum yields of these complexes make them interesting candidates for probes in sensing applications, especially [Ir(tpy-φ-CH(2)OH)(tpy-φ-NH(2))(2)](PF(6))(3) due to its unusual sensitivity to the solvent environment. 相似文献
993.
Using TMPZnCl·LiCl as a kinetically highly active base, nitriles and esters undergo a Pd-catalyzed α-arylation under mild conditions. Remarkably, in the case of α,β- or β,γ-unsaturated nitriles, a regioselective γ-arylation or a γ-alkenylation is observed. 相似文献
994.
Biran A Ben Yoav H Yagur-Kroll S Pedahzur R Buchinger S Shacham-Diamand Y Reifferscheid G Belkin S 《Analytical and bioanalytical chemistry》2011,400(9):3013-3024
A bacterial genotoxicity reporter strain was constructed in which the tightly controlled strong promoter of the Escherichia coli SOS response gene sulA was fused to the alkaline phosphatase-coding phoA reporter gene. The bioreporter responded in a dose-dependent manner to three model DNA-damaging agents—hydrogen peroxide,
nalidixic acid (NA), and mitomycin C (MMC)—detected 30–60 min after exposure. Detection thresholds were 0.15 μM for MMC, 7.5 μM
for nalidixic acid, and approximately 50 μM for hydrogen peroxide. A similar response to NA was observed when the bioreporter
was integrated into a specially designed, portable electrochemical detection platform. Reporter sensitivity was further enhanced
by single and double knockout mutations that enhanced cell membrane permeability (rfaE) and inhibited DNA damage repair mechanisms (umuD, uvrA). The rfaE mutants displayed a five- and tenfold increase in sensitivity to MMC and NA, respectively, while the uvrA mutation was advantageous in the detection of hydrogen peroxide. A similar sensitivity was displayed by the double rfaE/uvrA mutant when challenged with the pre-genotoxic agents 2-amino-3-methylimidazo[4,5-f]quinoline and 2-aminoanthracene following
metabolic activation with an S9 mammalian liver fraction. 相似文献
995.
Schmidt H Böttcher C Trampczynska A Clemens S 《Analytical and bioanalytical chemistry》2011,399(3):1355-1361
Nicotianamine (NA) is an important metal chelator, implicated in the intra- and intercellular trafficking of several transition
metal ions in plants. To decipher its roles in physiological processes such as micronutrient acquisition, distribution or
storage, fast and sensitive analytical techniques for quantification of this non-proteinogenic amino acid will be required.
The use of a recombinant Schizosaccharomyces pombe strain expressing a nicotianamine synthase (NAS) gene allowed for the production of [15N3]-NA, which was enriched from cell extracts through cation exchange and used for stable isotope dilution analysis of NA. Such
an approach should be widely applicable to important bioanalytes that are difficult to synthesize. The analytical procedure
comprises mild aqueous extraction and rapid Fmoc derivatization, followed by fast separation using ultra-performance liquid
chromatography (UPLC) and sensitive detection by positive ion electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS)
with a chromatographic cycle time of only 8 min. Derivatization was optimized with respect to incubation time and species
suitable for quantification. The limit of detection was 0.14 to 0.23 pmol in biological matrices with the response being linear
up to 42 pmol. Recovery rates were between 83% and 104% in various biological matrices including fission yeast cells, fungal
mycelium, plant leaves and roots. 相似文献
996.
Thomas A Höppner S Geyer H Schänzer W Petrou M Kwiatkowska D Pokrywka A Thevis M 《Analytical and bioanalytical chemistry》2011,401(2):507-516
A family of small peptides has reached the focus of doping controls representing a comparably new strategy for cheating sportsmen.
These growth hormone releasing peptides (GHRP) are orally active and induce an increased production of endogenous growth hormone
(GH). While the established test for exogenous GH fails, the misuse of these prohibited substances remains unrecognized. The
present study provides data for the efficient extraction of a variety of known drug candidates (GHRP-1, GHRP-2, GHRP-4, GHRP-5,
GHRP-6, alexamorelin, ipamorelin, and hexarelin) from human urine with subsequent mass spectrometric detection after liquid
chromatographic separation. The used method potentially enables the retrospective evaluation of the acquired data for unknown
metabolites by means of a non-targeted approach with high-resolution/high-accuracy full-scan mass spectrometry with additional
higher collision energy dissociation experiments. This is of great importance due to the currently unknown metabolism of most
of the targets and, thus, the method is focused on the intact peptidic drugs. Only the already characterised major metabolite
of GHRP-2 (d-Ala-d-2-naphthylAla-l-Ala, as well as its stable isotope-labelled analogue) was synthesised and implemented in the detection assay. Method validation
for qualitative purpose was performed with respect to specificity, precision (<20%), intermediate precision (<20%), recovery
(47–95%), limit of detection (0.2–1 ng/mL), linearity, ion suppression and stability. Two stable isotope-labelled internal
standards were used (deuterium-labelled GHRP-4 and GHRP-2 metabolite). The proof-of-principle was obtained by the analysis
of excretion study urine samples obtained from a single oral administration of 10 mg of GHRP-2. Here, the known metabolite
was detectable over 20 h after administration while the intact drug was not observed. 相似文献
997.
Ka Hin LeungBernhard Schmidt 《Journal of Combinatorial Theory, Series A》2011,118(3):908-919
Let n be a fixed positive integer. Every circulant weighing matrix of weight n arises from what we call an irreducible orthogonal family of weight n. We show that the number of irreducible orthogonal families of weight n is finite and thus obtain a finite algorithm for classifying all circulant weighing matrices of weight n. We also show that, for every odd prime power q, there are at most finitely many proper circulant weighing matrices of weight q. 相似文献
998.
Olaf Beyersdorff Arne Meier Sebastian M��ller Michael Thomas Heribert Vollmer 《Archive for Mathematical Logic》2011,50(7-8):727-742
Default logic is one of the most popular and successful formalisms for non-monotonic reasoning. In 2002, Bonatti and Olivetti introduced several sequent calculi for credulous and skeptical reasoning in propositional default logic. In this paper we examine these calculi from a proof-complexity perspective. In particular, we show that the calculus for credulous reasoning obeys almost the same bounds on the proof size as Gentzen??s system LK. Hence proving lower bounds for credulous reasoning will be as hard as proving lower bounds for LK. On the other hand, we show an exponential lower bound to the proof size in Bonatti and Olivetti??s enhanced calculus for skeptical default reasoning. 相似文献
999.
Qin T Wiedemair W Nau S Trattnig R Sax S Winkler S Vollmer A Koch N Baumgarten M List EJ Müllen K 《Journal of the American Chemical Society》2011,133(5):1301-1303
We present a novel core-shell-surface multifunctional structure for dendrimers using a blue fluorescent pyrene core with triphenylene dendrons and triphenylamine surface groups. We find efficient excitation energy transfer from the triphenylene shell to the pyrene core, substantially enhancing the quantum yield in solution and the solid state (4-fold) compared to dendrimers without a core emitter, while TPA groups facilitate the hole capturing and injection ability in the device applications. With a luminance of up to 1400 cd/m(2), a saturated blue emission CIE(xy) = (0.15, 0.17) and high operational stability, these dendrimers belong to the best reported fluorescence-based blue-emitting organic molecules. 相似文献
1000.
Giglio BC Schmidt VA Alexanian EJ 《Journal of the American Chemical Society》2011,133(34):13320-13322
The dioxygenation of alkenes using molecular oxygen and a simple hydroxamic acid derivative has been achieved. The reaction system consists of readily prepared methyl N-hydroxy-N-phenylcarbamate and molecular oxygen with a radical initiator, offering an alternative to common dioxygenation processes catalyzed by precious transition metals. This transformation capitalizes on the unique reactivity profile of hydroxamic acid derivatives in radical-mediated alkene addition processes. 相似文献