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排序方式: 共有400条查询结果,搜索用时 15 毫秒
101.
Tal S Salman H Abraham Y Botoshansky M Eichen Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(18):4858-4864
Photoinduced-electron-transfer (PET)-based chemosensing is a very elegant way of reporting the presence of a guest species in solution. This method was successfully applied for the detection of different ionic species, such as cations, anions, and protons. Herein, we report on the application of the PET chemosensing concept for the efficient and selective detection of different alkylating agents. 2-(2-Dimethylaminoethyl)benzo[de]isoquinoline-1,3-dione (1) was found to be a highly selective and effective PET chemosensor that turns luminescent upon reacting with different alkylating agents. This PET-based system detected even rather weak alkylating agents, such as dichloromethane. A PET-based sensor that consists of 1 as the active component could detect rather low concentrations of alkylating agents in solution and in the gas phase. 相似文献
102.
Effect of electronic polarization on charge-transport parameters in molecular organic semiconductors
Valeev EF Coropceanu V da Silva Filho DA Salman S Brédas JL 《Journal of the American Chemical Society》2006,128(30):9882-9886
Theoretical investigations of charge transport in organic materials are generally based on the "energy splitting in dimer" method and routinely assume that the transport parameters (site energies and transfer integrals) determined from monomer and dimer calculations can be reliably used to describe extended systems. Here, we demonstrate that this transferability can fail even in molecular crystals with weak van der Waals intermolecular interactions, due to the substantial (but often ignored) impact of polarization effects, particularly on the site energies. We show that the neglect of electronic polarization leads to qualitatively incorrect values and trends for the transfer integrals computed with the energy splitting method, even in simple prototypes such as ethylene or pentacene dimers. The polarization effect in these systems is largely electrostatic in nature and can change dramatically upon transition from a dimer to an extended system. For example, the difference in site energy for a prototypical "face-to-edge" one-dimensional stack of pentacene molecules is calculated to be 30% greater than that in the "face-to-edge" dimer, whereas the site energy difference in the pentacene crystal is vanishingly small. Importantly, when computed directly in the framework of localized monomer orbitals, the transfer integral values for dimer and extended systems are very similar. 相似文献
103.
We report the first experimental demonstration of vibrational mode-dependent enhancement in photodissociation and photoionization of a seven atom molecule, methylamine (CH(3)NH(2)). The fundamental C-H stretches and the overtones or combinations of CH(3) bends were prepared via stimulated Raman excitation (SRE) prior to their 243.135 nm one-photon dissociation or two-photon ionization. The photodissociation or photoionization of the vibrationally excited molecules was achieved via 10 ns delayed or temporally overlapping SRE and UV pulses, respectively. It is shown that bending modes are more effective than stretches in promoting photodissociation and photoionization, since their UV excitation is favored by larger Franck Condon factors. This behavior provides clear evidence for vibrational mode-dependence in a relatively large molecule with a torsional degree of freedom, indicating that these modes survive intramolecular vibrational redistribution on a time scale considerably longer than hitherto inferred from previous studies. 相似文献
104.
The carbon -13 chemical shift of nine new substituted 2-amino benzothiazole is presented. The calculated chemical shift, using substituent parameters, agrees with the observed one. 相似文献
105.
Simple Zeros of the Riemann Zeta-Function 总被引:1,自引:0,他引:1
Assuming the Riemann Hypothesis, Montgomery showed by meansof his pair correlation method that at least two-thirds of thezeros of Riemann's zeta-function are simple. Later he and Taylorimproved this to 67.25 percent and, more recently, Cheer andGoldston increased the percentage to 67.2753. Here we proveby a new method that if the Riemann and Generalized LindelöofHypotheses hold, then at least 70.3704 percent of the zerosare simple and at least 84.5679 percent are distinct. Our methoduses mean value estimates for various functions defined by Dirichletseries sampled at the zeros of the Riemann zeta-function. 1991Mathematics Subject Classification: 11M26. 相似文献
106.
107.
Modifications to antibody affinity electrophoresis for improved detection of proteins have been developed. The bifunctional linker glutaraldehyde is added to the polyacrylamide gel solution for better incorporation of the bait antibody into a distinct region of a 10% w/v polyacrylamide gel. The addition of glutaraldehyde alleviates the need of an electrophoresis buffer with a specific pH. The protein sample to be analyzed is treated with 2% w/v sodium dodecyl sulfate (SDS) to ensure that they carry a negative charge. The negative charge will allow the proteins to migrate towards the cathode and hence pass through the area embedded with the bait antibody. It is observed that electrophoretic migration of bovine serum albumin (BSA) or protein G ceases upon encounter with anti-BSA whereas proteins ovalbumin, beta-lactoglobulin A, and myoglobin migrate freely. However, the addition of 0.1% w/v SDS in the native gel running buffer disrupts the antibody-antigen bond and neither BSA nor protein G can be captured by anti-BSA. 相似文献
108.
Salman S. Alharthi Ahmed Noah Badr Karolina Gromadzka Kinga Stuper-Szablewska Adel Gabr Abdel-Razek Khaled Selim 《Molecules (Basel, Switzerland)》2021,26(23)
Mandarin is a favorite fruit of the citrus family. Mandarin seeds are considered a source of nontraditional oil obtained from byproduct materials. This investigation aimed to assess the biomolecules of mandarin seeds and evaluated their antimycotic and antimycotoxigenic impact on fungi. Moreover, it evaluated the protective role of mandarin oil against aflatoxin toxicity in cell lines. The two types of extracted oil (fixed and volatile) were ecofriendly. The fatty acid composition, tocopherol, sterols, and carotenoids were determined in the fixed oil, whereas volatiles and phenolics were estimated in the essential oil. A mixture of the two oils was prepared and evaluated for its antimicrobial impact. The reduction effect of this mixture was also investigated to reduce mycotoxin secretion using a simulated experiment. The protective effect of the oil was evaluated using healthy strains of cell lines. Fixed oil was distinguished by the omega fatty acid content (76.24%), lutein was the major carotenoid (504.3 mg/100 g) and it had a high β-sitosterol content (294.6 mg/100 g). Essential oil contained limonene (66.05%), α-pinene (6.82%), β-pinene (4.32%), and γ-terpinene (12.31%) in significant amounts, while gallic acid and catechol were recorded as the dominant phenolics. Evaluation of the oil mix for antimicrobial potency reflected a considerable impact against pathogenic bacteria and toxigenic fungi. By its application to the fungal media, this oil mix possessed a capacity for reducing mycotoxin secretion. The oil mix was also shown to have a low cytotoxic effect against healthy strains of cell lines and had potency in reducing the mortality impact of aflatoxin B1 applied to cell lines. These results recommend further study to involve this oil in food safety applications. 相似文献
109.
Salman R. Salman Jabor K. Jabor 《Journal of inclusion phenomena and macrocyclic chemistry》1999,33(1):17-26
The UV-Visible spectra of Cryptand (2,2,2) and Kryptofix 5 as donors, and TCNE (tetracyanoethylene), DDQ (2,3-dichloro-5,6- dicyano-1,4 benzoquinone) and PA (picric acid) as acceptors were studied. Charge transfer (CT) spectra were obtained for these systems. It was found that potassium halides have little effect on the spectra. The major process was due to an electron transfer from the donor to the acceptor. This revealed itself in very high conductivity values for the CT solutions in comparison to that of the donor or the acceptor solutions. The infrared and proton NMR spectra of the complexes indicated a strong interaction between the donor and the acceptor. 相似文献
110.
Lee BS Krisnanchettiar S Lateef SS Gupta S 《Rapid communications in mass spectrometry : RCM》2005,19(7):886-892
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to detect biotinylated peptides captured by avidin functional affinity electrophoresis (AFAEP). Peptide samples loaded onto AFAEP were heated with sodium dodecyl sulfate to ensure that the peptides are negatively charged, and thus migrate electrophoretically toward the cathode through the embedded avidin zone in the middle of the gel. To detect the biotinylated peptides, the band containing the avidin-biotinylated peptide complexes was excised from a 7.5% w/v native polyacrylamide gel, and biotinylated peptides were extracted with aqueous 95% v/v formamide (pH 8.2), aqueous 6 M guanidine HCl (pH 1.5), or water, at temperatures from 4 to 95 degrees C for periods from 5 min to 24 h. It was observed that all three solvents are capable of extracting biotinylated peptides and avidin from the gel, but the best results were obtained with aqueous 95% v/v formamide (pH 8.2) at 65 degrees C for 20 min. However, some AFAEP-captured biotinylated peptides are not stable and are extensively modified by formamide during extraction at too high a temperature or too long an extraction time. 相似文献