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71.
Complex 1 undergoes H/D scrambling in methanol without concomitant liberation of either methane or dihydrogen (k(H)/k(D) = 0.76, 55 degrees C). The measured isotope effect was proposed to directly relate to the initial reductive coupling step in reductive elimination reactions. 相似文献
72.
Dr. Marek Komisarski Dr. Yazmin M. Osornio Prof. Jay S. Siegel Prof. Ehud M. Landau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1262-1267
A classical conundrum in origin‐of‐life studies relates to the nature of the first chemical system: was it a carrier of genetic information or a facilitator of cellular compartmentalization? Here we present a system composed of tailor‐made nucleolipids and hydrated monoolein, which assemble at ambient temperatures to form host–guest lipidic cubic phase (LCP) materials that are stable in bulk water and can perform both functions. As such, they may represent a molecular model for a protocell in origin‐of‐life studies. Nucleolipids within the lipidic material sequester and bind selectively complementary oligonucleotide sequences from solution by virtue of base‐pairing; noncomplementary sequences diffuse freely between the LCP material and the bulk aqueous environment. Sequence specific enrichment of nucleic acids within the LCP material demonstrates an effective mechanism for selection of genetic material in these cell‐mimetic systems. 相似文献
73.
Inactivation of Trypanosoma cruzi Trypomastigote Forms in Blood Components with a Psoralen and Ultraviolet A Light 总被引:1,自引:0,他引:1
Paul Gottlieb Henrietta Margolis-Nunno Richard Robinson Li-Gang Shen Eleanor Chimezie Bernard Horowitz Ehud Ben-Hur 《Photochemistry and photobiology》1996,63(5):562-565
Inactivation of the blood-borne parasite Trypanosoma cruzi by UVA and 4'-aminomethyl-4,5',8-trimethylpsor-alen (AMT) was studied in the blood components fresh frozen plasma (FFP) and platelet concentrate (PC). The AMT was utilized at a concentration of 50 μg/mL and the inactivation procedure included the flavonoid rutin (at 0.35 mM), a quencher of type I and type II photo-reactants, which we have previously found to maintain platelet integrity during this treatment regimen. Within both FFP and PC, complete inactivation of the infective form of T. cruzi , the trypomastigote, was achieved at a UVA (320–400 nm radiation) fluence of 4.2 J/cm2 . We note that while the infectivity of the parasite is eliminated at 4.2 J/cmZ the trypomastigote motility continues for at least 16 h post-treatment and is inhibited only after much higher light doses. Isolation of total DNA from the parasite cells after treatment in the presence of 3 H-AMT indicated that at the lethal UVA fluence about 0.5 AMT adducts per kilobase pairs occurred. These results suggest that this psoralen plus UVA methodology, which shows promise in enhancing the viral safety of PC, may in addition eliminate bloodborne T. cruzi , the causative agent of Chagas disease. 相似文献
74.
Ehud Friedgut 《Journal of Combinatorial Theory, Series A》2005,111(2):239-244
Let p?1/2 and let μp be the product measure on {0,1}n, where μp(x)=p∑xi(1-p)n-∑xi. Let A⊂{0,1}n be an intersecting family, i.e. for every x,y∈A there exists 1?i?n such that xi=yi=1. Then μp(A)?p. Our proof uses a probabilistic trick first applied by Katona to prove the Erd?s-Ko-Rado theorem. 相似文献
75.
Ehud Hrushovski Ya'acov Peterzil Anand Pillay 《Journal of the American Mathematical Society》2008,21(2):563-596
We discuss measures, invariant measures on definable groups, and genericity, often in an NIP (failure of the independence property) environment. We complete the proof of the third author's conjectures relating definably compact groups in saturated -minimal structures to compact Lie groups. We also prove some other structural results about such , for example the existence of a left invariant finitely additive probability measure on definable subsets of . We finally introduce the new notion of ``compact domination" (domination of a definable set by a compact space) and raise some new conjectures in the -minimal case.
76.
Irit Dinur Ehud Friedgut Guy Kindler Ryan O’Donnell 《Israel Journal of Mathematics》2007,160(1):389-412
In this paper we consider bounded real-valued functions over the discrete cube, f: {−1, 1}n → [−1, 1]. Such functions arise naturally in theoretical computer science, combinatorics, and the theory of social choice.
It is often interesting to understand when these functions essentially depend on few coordinates. Our main result is a dichotomy
that includes a lower bound on how fast the Fourier coefficients of such functions can decay: we show that
unless f depends essentially only on 2
O(k) coordinates. We also show, perhaps surprisingly, that this result is sharp up to the log k factor. p ]The same type of result has already been proven (and shown useful) for Boolean functions [Bou02, KS]. The proof
of these results relies on the Booleanity of the functions, and does not generalize to all bounded functions. In this work
we handle all bounded functions, at the price of a much faster tail decay. As already mentioned, this rate of decay is shown to be both roughly
necessary and sufficient. p ]Our proof incorporates the use of the noise operator with a random noise rate and some extremal
properties of the Chebyshev polynomials.
Research supported in part by the Israel Science Foundation, grant no. 0329745.
This work was completed while the author was at the Institute for Advanced Study, Princeton, NJ. The material is based upon
work supported in part by the National Science Foundation under agreement No. CCR-0324906. Recommendations expressed in this
material are those of the authors and do not necessarily reflect the views of the National Science Foundation. 相似文献
77.
Dr. Yaron Bram Ayala Lampel Dr. Ronit Shaltiel‐Karyo Anat Ezer Dr. Roni Scherzer‐Attali Prof. Dr. Daniel Segal Prof. Dr. Ehud Gazit 《Angewandte Chemie (International ed. in English)》2015,54(7):2062-2067
Amyloid deposits are pathological hallmark of a large group of human degenerative disorders of unrelated etiologies. While accumulating evidence suggests that early oligomers may account for tissue degeneration, most detection tools do not allow the monitoring of early association events. Here we exploit bimolecular fluorescence complementation analysis to detect and quantify the dimerization of three major amyloidogenic polypeptides; islet amyloid polypeptide, β‐amyloid and α‐synuclein. The constructed systems provided direct visualization of protein‐protein interactions in which only assembled dimers display strong fluorescent signal. Potential inhibitors that interfere with the initial intermolecular interactions of islet amyloid polypeptide were further identified using this system. Moreover, the identified compounds were able to inhibit the aggregation and cytotoxicity of islet amyloid polypeptide, demonstrating the importance of targeting amyloid dimer formation for future drug development. 相似文献
78.
Dr. Kai Tao Yiming Tang Dr. Sigal Rencus-Lazar Yifei Yao Dr. Bin Xue Dr. Sharon Gilead Prof. Guanghong Wei Prof. Ehud Gazit 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19199-19203
Bottom-up self-assembled bioinspired materials have attracted increasing interest in a variety fields. The use of peptide supramolecular semiconductors for optoelectronic applications is especially intriguing. However, the characteristic thermal unsustainability limits their practical application. Here, we report the thermal sustainability of cyclo-ditryptophan assemblies up to 680 K. Non-covalent interactions underlie the stability mechanism, generating a low exciton-binding energy of only 0.29 eV and a high thermal-quenching-activation energy of up to 0.11 eV. The contributing forces comprise predominantly of aromatic interactions, followed by hydrogen bonding between peptide molecules, and, to a lesser extent, water-mediated associations. This thermal sustainability results in a temperature-dependent conductivity of the supramolecular semiconductors, showing 93 % reduction of the resistance from 320 K to 440 K. Our results establish thermo-sustainable peptide self-assembly for heat-sensitive applications. 相似文献
79.
Sinha MK Reany O Yefet M Botoshansky M Keinan E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(18):5589-5605
Bistable rotaxanes are important design elements of molecular devices for a broad range of applications, such as controlled drug release, molecular rotary motors, and chemical sensors. The host-guest complexes of cucurbit[6]uril and 1,4-bis(alkylaminomethyl)benzene were found to exhibit two stable binding modes with an unexpectedly high barrier between them. Their structural and dynamic properties, kinetic and thermodynamic parameters, as well as different chemical reactivity towards the azide-alkyne [3+2] cycloaddition reaction (click chemistry), were discovered by NMR spectroscopy, X-ray crystallography, and isothermal titration microcalorimetry. The highly stable 2:1 complex, which is formed at room temperature, was found to be a kinetic product, which may be converted to the thermodynamic 1:1 complex upon prolonged heating to 100?°C. The latter is a very stable rotaxane despite the fact that it lacks bulky end groups. 相似文献
80.
Meyer MR Vollmar C Schwaninger AE Wolf E Maurer HH 《Journal of mass spectrometry : JMS》2012,47(2):253-262
3-Bromomethcathinone (3-BMC) and 3-Fluoromethcathinone (3-FMC) are two new designer drugs, which were seized in Israel during 2009 and had also appeared on the illicit drug market in Germany. These two compounds were sold via the Internet as so-called "bath salts" or "plant feeders." The aim of the present study was to identify for the first time the 3-BMC and 3-FMC Phase I and II metabolites in rat urine and human liver microsomes using GC-MS and LC-high-resolution MS (HR-MS) and to test for their detectability by established urine screening approaches using GC-MS or LC-MS. Furthermore, the human cytochrome-P450 (CYP) isoenzymes responsible for the main metabolic steps were studied to highlight possible risks of consumption due to drug-drug interaction or genetic variations. For the first aim, rat urine samples were extracted after and without enzymatic cleavage of conjugates. The metabolites were separated and identified by GC-MS and by LC-HR-MS. The main metabolic steps were N-demethylation, reduction of the keto group to the corresponding alcohol, hydroxylation of the aromatic system and combinations of these steps. The elemental composition of the metabolites identified by GC-MS could be confirmed by LC-HR-MS. Furthermore, corresponding Phase II metabolites were identified using the LC-HR-MS approach. For both compounds, detection in rat urine was possible within the authors' systematic toxicological analysis using both GC-MS and LC-MS(n) after a suspected recreational users dose. Following CYP enzyme kinetic studies, CYP2B6 was the most relevant enzyme for both the N-demethylation of 3-BMC and 3-FMC after in vitro-in vivo extrapolation. 相似文献