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101.
6MAP is a fluorescent analogue of adenine that undergoes Watson-Crick base pairing and base stacking in double-stranded DNA. The one-photon absorption spectrum of 6MAP is characterized by a maximum around 330 nm with moderate quantum yield fluorescence centered at about 420 nm. To take advantage of this probe for confocal and single-molecule microscopy, it would be advantageous to be able to excite the analogue via two photons. We report the first determination of the two-photon excitation cross section and spectrum for 6MAP from 614 to 700 nm. The power dependence of the fluorescence indicates that emission results from the absorption of two photons. The one-photon and two-photon emission line shapes are identical within experimental error. A study of the concentration dependence of the fluorescence yield for one-photon excitation shows no measurable quenching up to about 5 microM. The maximum in the two-photon excitation spectrum gives a two-photon cross section, delta(TPE), of 3.4 +/- 0.1 Goeppert-Mayer (G.M.) at 659 nm, which correlates well with the one-photon absorption maximum. This compares quite favorably with cross sections of various naturally fluorescent biological molecules such as flavins and nicotiamide. In addition, we have also obtained the two-photon-induced fluorescence emission spectrum of quinine sulfate. It is approximately the same as that for one-photon excitation, suggesting that two-photon excitation of quinine sulfate may be used for calibration purposes. 相似文献
102.
103.
Vincent J. Kalish Robert L. Shone Steven W. Kramer Paul W. Collins Kevin A. Babiak Kathleen T. McLaughlin 《合成通讯》2013,43(11):1641-1645
Hydrozirconation-iodination of a terminal acetylene followed by lithium-iodide exchange and finally dilithio cyanocuprate mediated conjugate addition to an appropriate cyclopentenone is reported as an efficient method for the synthesis of prostaglandin analogues. 相似文献
104.
Anne‐Catherine Bédard Prof. Dr. Shawn K. Collins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(6):2108-2113
The aggregation properties of poly(ethylene glycol) (PEG) can be exploited in organic synthesis to control dilution effects. Through the use of solvent mixtures containing PEG400/MeOH, macrocyclization by Glaser–Hay coupling can be conducted at high concentrations. The origin of the selectivity has been studied by using surface tension measurements, UV spectroscopy, and chemical tagging and demonstrates the dependence of the yield and selectivity on the aggregation of PEG400 and its ability to preferentially solubilize organic substrates, resulting in a phase separation from the catalyst system. 相似文献
105.
Umme Kalsoom Michael C. Breadmore Rosanne M. Guijt Mary C. Boyce 《Electrophoresis》2014,35(23):3379-3386
Osmoregulants are the substances that help plants to tolerate environmental extremes such as salinity and drought. Proline and betaine are two of the most commonly studied osmoregulants. An indirect UV CE method has been developed for simultaneous determination of these osmoregulants. A variety of reported probes and compounds were examined as potential probes for the indirect detection of proline and betaine. Mobility and UV‐absorption properties highlighted sulfanilamide as a potential probe for indirect analysis of proline and betaine. Using 5 mM sulfanilamide at pH 2.2 with UV detection at 254 nm, proline and betaine were separated in less than 15 min. The LODs for proline and betaine were 11.6 and 28.3 μM, respectively. The developed method was successfully applied to quantification of these two osmoregulants in spinach and beetroot samples. 相似文献
106.
Bernice H. L. Oh Alexander Bismarck Mary B. Chan‐Park 《Macromolecular rapid communications》2015,36(4):364-372
High‐porosity interconnected, thermoresponsive macroporous hydrogels are prepared from oil‐in‐water high internal phase emulsions (HIPEs) stabilized by gelatin‐graft‐poly(N‐isopropylacrylamide). PolyHIPEs are obtained by gelling HIPEs utilizing the thermoresponsiveness of the copolymer components. PolyHIPEs properties can be controlled by varying the aqueous phase composition, internal phase volume ratio, and gelation temperature. PolyHIPEs respond to temperature changes experienced during cell seeding, allowing fibroblasts to spread, proliferate, and penetrate into the scaffold. Encapsulated cells survive ejection of cell‐laden hydrogels through a hypodermic needle. This system provides a new strategy for the fabrication of safe injectable biocompatible tissue engineering scaffolds.
107.
The spectroscopic properties of Nω-nitro-l-arginine were investigated by FT-IR, UV-VIS, and 1H NMR spectra. Geometrical parameters and energies were calculated using the density functional theory (DFT) B3LYP method with the 6-311G basis set. Geometrical optimization of the molecule has been performed, vibrational spectra have been calculated, and fundamental vibrations have been determined from the total energy distribution (TED) of the vibrational modes. The HOMO-LUMO analysis is carried out for various electric fields (0.0–0.025 A?1). The HOMO-LUMO gap is decreased while increasing the electric field. The calculated quantum chemical parameters are calculated and correlated to the inhibition efficiency, A Mullliken population was also important for determining local reactivity by indicating reactive centers and identifying potential nucleophilic and electrophilic attack sites. Charge transfer occurs inside the compound based on the HOMO LUMO gap. Calculations of DFT were evaluated in their ability to predict inhibition efficiency. 相似文献
108.
Queiroz Ana Luiza P. Kerins Brian M. Yadav Jayprakash Farag Fatma Faisal Waleed Crowley Mary Ellen Lawrence Simon E. Moynihan Humphrey A. Healy Anne-Marie Vucen Sonja Crean Abina M. 《Cellulose (London, England)》2021,28(14):8971-8985
Cellulose - Microcrystalline cellulose (MCC) is a semi-crystalline material with inherent variable crystallinity due to raw material source and variable manufacturing conditions. MCC crystallinity... 相似文献
109.
Anitha Kumary Vidyadharan Divya Jayan T. E. Mary Nancy 《Journal of Solid State Electrochemistry》2014,18(9):2513-2519
A novel electrochemical sensor based on nickel-doped cobalt ferrite nanoparticles (Ni0.1Co0.9Fe2O4)-modified glassy carbon electrode (NCF/GCE) was presented for the sensitive detection of paracetamol. Experimental conditions such as pH, applied potentials and concentration were investigated using cyclic voltammetric and chronoamperometric techniques. The modified electrode exhibited excellent catalytic response towards the oxidation of paracetamol with good reproducibility. The overpotential for oxidation of paracetamol is decreased, and the current response enhanced significantly on the modified electrode in comparison with that of bare electrode. Linear calibration curve is obtained over the range 2 μM to 8,000 μM having a detection limit of 11 nM. The modified electrode facilitated the simultaneous detection of paracetamol, ascorbic acid, and dopamine with good reproducibility. 相似文献
110.
Tuning Thiophene with Phosphorus: Synthesis and Electronic Properties of Benzobisthiaphospholes 下载免费PDF全文
Yunyan Qiu Joshua C. Worch Danielle N. Chirdon Aman Kaur Andrew B. Maurer Samuel Amsterdam Christopher R. Collins Prof. Tomislav Pintauer Prof. David Yaron Prof. Stefan Bernhard Prof. Kevin J. T. Noonan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7746-7751
1,4‐Dimercapto‐2,5‐diphosphinobenzene and 3,6‐bis(hexyloxy)‐1,4‐dimercapto‐2,5‐diphosphinobenzene were synthesized and combined with various acid chlorides to obtain a series of benzobisthiaphospholes. Electrochemical and photophysical properties of the substituted benzobisthiaphospholes have been evaluated, and the observed reductions are more facile than the related benzothiaphospholes and 2,6‐diphenylbenzobisthiazole. A benzobisthiaphosphole with C6H4‐p‐CN substituents was reduced at E1/2=?1.08 V (vs. saturated calomel electrode (SCE)). X‐ray diffraction data for several of these phosphorus heterocycles has been obtained, and DFT calculations at the B3LYP level have been performed. 相似文献