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111.
Sabelle S Renard PY Pecorella K de Suzzoni-Dézard S Créminon C Grassi J Mioskowski C 《Journal of the American Chemical Society》2002,124(17):4874-4880
Acetylcholinesterase is one of the most widely used and studied enzymes. Not only does this enzyme regulate neurotransmission (and thus play a key role in neurodegenerative processes) but it is also a prime target for pest control agents and warfare agents. Above all, due to its particularly high turnover rate, acetylcholinesterase is among the most efficient reporter enzymes yet described (for use as enzymatic tracer in immunoassays, for instance). However, its activity is detected through a colorimetric reagent, the Ellman reagent, which displays low detection limits and is often subject to background perturbations. In the course of our search for a more sensitive detection assay, we describe here a first-generation 1,2-dioxetane chemiluminescent probe, based on chemically induced electron exchange luminescence, which has an approximately 10 times lower detection limit than the Ellman colorimetric assay (2.5 x 10(-19) mol for Electrophorus electricus AChE in its tetrameric form). 相似文献
112.
Karine Chamaillard Jean-Pierre J. Lafon 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):519-528
In order to study the effect of shape on the optical properties of dust grains, we statistically analyze the linear polarized scattered light. We start by examining a homogeneous spherical grain using the discrete dipole approximation (DDA) Draine (Astrophys J 1988;333:848). Using a uniform law we remove elements of matter on the surface of the grain to describe a random roughness. Then, for various scattering angles, the linear polarization Pl is calculated. We successively repeat the simulation in order to obtain a sample of random variables constituting the values Pl of the linear polarization. The analysis of the results is then achieved through a Gaussian kernel method which provides the probability density function of Pl for each scattering angle. We present the results for a typical interstellar grain of water–ice with radius a comparable to the incident wavelength λ so that the parameter size x≡2πa/λ1. We apply this method for two wavelengths in the near IR, when water–ice is transparent at 1.9 μm, and, when water–ice is absorbing at 3.1 μm. We find that the shape of the density function of the linear polarization is asymmetric to the mean value of the density function and non-unimodal for several scattering angles. This allows us to separate the effects of roughness from those of volume. When water–ice is absorbing, we also observe a significant shift of the polarization peak toward greater scattering angles. 相似文献
113.
114.
Cline Taglang Luis Miguel Martínez‐Prieto Iker delRosal Laurent Maron Romuald Poteau Karine Philippot Bruno Chaudret Serge Perato Anaïs SamLone Cline Puente Christophe Dugave Bernard Rousseau Grgory Pieters 《Angewandte Chemie (International ed. in English)》2015,54(36):10474-10477
The activation of C H bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific C H activation has been developed to date. We herein report an enantiospecific C H activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α‐position of the directing heteroatom results from a four‐membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles. 相似文献
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116.
Dr. Edmond Gravel Abha Harfouche Dr. Rim Salame Karine Leblanc Dr. Alexandre Maciuk Prof. Dr. Erwan Poupon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(43):14515-14520
Mixtures of tryptamine and reactive C5 units, presumably derived from lysine in nature, were studied to ascertain the spontaneous formation of the complex polycyclic alkaloid nitrarine. Several indolic compounds tracing the unified metabolism within the Nitraria genus were also characterized. 相似文献
117.
Reductive Coupling of Diynes at Rhodium Gives Fluorescent Rhodacyclopentadienes or Phosphorescent Rhodium 2,2’‐Biphenyl Complexes
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Carolin Sieck Dr. Meng Guan Tay Dr. Marie‐Hélène Thibault Dr. Robert M. Edkins Dr. Karine Costuas Prof. Dr. Jean‐François Halet Dr. Andrei S. Batsanov Dr. Martin Haehnel Dr. Katharina Edkins Dr. Andreas Lorbach Dr. Andreas Steffen Prof. Dr. Todd B. Marder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10523-10532
Reactions of [Rh(κ2‐O,O‐acac)(PMe3)2] (acac=acetylacetonato) and α,ω‐bis(arylbutadiynyl)alkanes afford two isomeric types of MC4 metallacycles with very different photophysical properties. As a result of a [2+2] reductive coupling at Rh, 2,5‐bis(arylethynyl)rhodacyclopentadienes ( A ) are formed, which display intense fluorescence (Φ=0.07–0.54, τ=0.2–2.5 ns) despite the presence of the heavy metal atom. Rhodium biphenyl complexes ( B ), which show exceptionally long‐lived (hundreds of μs) phosphorescence (Φ=0.01–0.33) at room temperature in solution, have been isolated as a second isomer originating from an unusual [4+2] cycloaddition reaction and a subsequent β‐H‐shift. We attribute the different photophysical properties of isomers A and B to a higher excited state density and a less stabilized T1 state in the biphenyl complexes B , allowing for more efficient intersystem crossing S1→Tn and T1→S0. Control of the isomer distribution is achieved by modification of the bis‐ (diyne) linker length, providing a fundamentally new route to access photoactive metal biphenyl compounds. 相似文献
118.
Dr. Giuseppe Lamanna Dr. Cristian R. Smulski Neila Chekkat Dr. Karine Estieu‐Gionnet Dr. Gilles Guichard Prof. Sylvie Fournel Dr. Alberto Bianco 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(5):1762-1768
We have developed a straightforward strategy to multimerize an apoptogenic peptide that mimics the natural tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) by using adamantane‐based dendrons as multivalent scaffolds. The selective binding affinity of the ligands to TRAIL receptor 2 (TR2) was studied by surface plasmon resonance, thus demonstrating that the trimeric and hexameric forms of the peptide exert an increased affinity of about 1500‐ and 20 000‐fold, respectively, relative to the monomer. Moreover, only the trimeric and hexameric ligands were able to induce cell death in TR2 expressing cells (BJAB), thus confirming that a multivalent form of the peptide is necessary to trigger a substantial TR2‐dependent apoptotic response in vitro. These results provide interesting insight into the multivalency effect on biological ligand/receptor interactions for future therapeutic applications. 相似文献
119.
Karine Le Bris Roopa Pandharpurkar 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(8):1280-1285
The temperature dependence of the infrared absorption cross-sections of CFC-113 (1,1,2-trichlorotrifluoroethane) in a pure vapor phase has been recorded in the 600-1250 cm−1 spectral region using Fourier transform spectroscopy. Spectra at 0.05 cm−1 resolution have been used to derive the integrated band strengths of the five main absorption bands over a range of temperatures from 223 to 283 K. Our results show good agreement with previously published data. The new cross-sections will allow more accurate retrieval of atmospheric CFC-113 concentrations using infrared spectroscopic techniques. 相似文献
120.
Enantioselective hydroxylation of one specific methylene in the presence of many similar groups is debatably the most challenging chemical transformation. Although chemists have recently made progress toward the hydroxylation of inactivated C-H bonds, enzymes such as P450s (CYPs) remain unsurpassed in specificity and scope. The substrate promiscuity of many P450s is desirable for synthetic applications; however, the inability to predict the products of these enzymatic reactions is impeding advancement. We demonstrate here the utility of a chemical auxiliary to control the selectivity of CYP3A4 reactions. When linked to substrates, inexpensive, achiral theobromine directs the reaction to produce hydroxylation or epoxidation at the fourth carbon from the auxiliary with pro-R facial selectivity. This strategy provides a versatile yet controllable system for regio-, chemo-, and stereoselective oxidations at inactivated C-H bonds and demonstrates the utility of chemical auxiliaries to mediate the activity of highly promiscuous enzymes. 相似文献