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91.
92.
Raghunath O. Ramabhadran Mohamed Husaini bin Abdul Rahman Steven J. Collier Richard C. Storr Roderick W. Bates 《Tetrahedron》2018,74(1):1-5
Trapping of a pyrimidinone-derived o-quinodimethane with tetraphenylcyclopentadienone gives a mixture of the [4 + 2] and formal [4 + 4] adducts. Computational studies show that the latter arises by a sequence of [4 + 2] cycloaddition, homolysis, radical recombination to a spiro-tetrahydrofuran and Claisen rearrangement under the thermolytic conditions. 相似文献
93.
Caltagirone C Bates GW Gale PA Light ME 《Chemical communications (Cambridge, England)》2008,(1):61-63
Sulfonamide groups, commonly used as neutral hydrogen bond donors in a wide variety of anion receptors, deprotonate upon addition of certain basic anionic guests in two simple functionalised ureas. 相似文献
94.
Yang XL Kapoor M Otero FJ Slike BM Tsuruta H Frausto R Bates A Ewalt KL Cheresh DA Schimmel P 《Chemistry & biology》2007,14(12):1323-1333
Disease-causing mutations occur in genes for aminoacyl tRNA synthetases. That some mutations are dominant suggests a gain of function. Native tRNA synthetases, such as tyrosyl-tRNA synthetase (TyrRS) and tryptophanyl-tRNA synthetase, catalyze aminoacylation and are also procytokines that are activated by natural fragmentation. In principle, however, gain-of-function phenotypes could arise from mutational activation of synthetase procytokines. From crystal structure analysis, we hypothesized that a steric block of a critical Glu-Leu-Arg (ELR) motif in full-length TyrRS suppresses the cytokine activity of a natural fragment. To test this hypothesis, we attempted to uncover ELR in the procytokine by mutating a conserved tyrosine (Y341) that tethers ELR. Site-specific proteolytic cleavage and small-angle X-ray scattering established subtle opening of the structure by the mutation. Strikingly, four different assays demonstrated mutational activation of cytokine functions. The results prove the possibilities for constitutive gain-of-function mutations in tRNA synthetases. 相似文献
95.
Two cleft-like anion receptors have been synthesised that contain indole hydrogen-bond donors and show fluoride selectively in a DMSO-water solution with crystallographic studies showing a 'twisted' binding mode for fluoride in the solid state. 相似文献
96.
Resonance Raman and infrared absorption spectra of ClO3 radicals have been observed from measurements of crystalline NaClO3 irradiated at 77 K with 1.5 MeV electrons. The ClO3 radicals occupy two sets of nonequivalent sites; radicals at one site are observed from resonance scattering using 6328 Å excitation while those at the other site are observed from resonance scattering with 5145 Å excitation. The red sensitive radicals decompose at 77 K with a half-life of ≈29 min while the green sensitive radicals are more stable at this temperature. 相似文献
97.
Infrared fluorescence observed after exciting to ν6 (ν=1) of CD3H with a Q-switched CO2 laser yields the exponential deactivation rate constant of 0.84 ms?1 torr?1. Rate constants for deactivation of CD3H by rare gases vary from 1.4 (for He) to 0.029 (for Xe) ms?1 torr?1. 相似文献
98.
Luiz L. Mafra Jr. Claude Léger Stephen S. Bates Michael A. Quilliam 《Journal of chromatography. A》2009,1216(32):6003-6011
Quantitation of trace levels of domoic acid (DA) in seawater samples usually requires labour-intensive protocols involving chemical derivatization with 9-fluorenylmethylchloroformate and liquid chromatography with fluorescence detection (FMOC–LC–FLD). Procedures based on LC–MS have been published, but time-consuming and costly solid-phase extraction pre-concentration steps are required to achieve suitable detection limits. This paper describes an alternative, simple and inexpensive LC method with ultraviolet detection (LC–UVD) for the routine analysis of trace levels of DA in seawater without the use of sample pre-concentration or derivatization steps. Qualitative confirmation of DA identity in dubious samples can be achieved by mass spectrometry (LC–MS) using the same chromatographic conditions. Addition of an ion-pairing/acidifying agent (0.15% trifluoroacetic acid) to sample extracts and the use of a gradient elution permitted the direct analysis of large sample volumes (100 μl), resulting in both high selectivity and sensitivity (limit of detection = 42 pg ml−1 by LC–UVD and 15 pg ml−1 by LC–MS). Same-day precision varied between 0.4 and 5%, depending on the detection method and DA concentration. Mean recoveries of spiked DA in seawater by LC–UVD were 98.8% at 0.1–10 ng ml−1 and 99.8% at 50–1000 ng ml−1. LC–UVD exhibited strong correlation with FMOC–LC–FLD during inter-laboratory analysis of Pseudo-nitzschia multiseries cultures containing 60–2000 ng DA ml−1 (r2 > 0.99), but more variable results were obtained by LC–MS (r2 = 0.85). This new technique was used to confirm the presence of trace DA levels in low-toxicity Pseudo-nitzschia spp. isolates (0.2–1.6 ng ml−1) and in whole-water field samples (0.3–5.8 ng ml−1), even in the absence of detectable Pseudo-nitzschia spp. cells in the water column. 相似文献
99.
In this paper we give a computational strategy for constructing the normalizer of a p-subgroup in a finite group.
Received: 31 January 2008 相似文献
100.
Plutonium-enriched layer has been observed in corroded spent uranium oxide fuel (CSNF). These Pu-enriched regions were examined with analytical transmission electron microscopy combined with electron energy-loss spectroscopy (EELS). The enriched region also contained U, Am, Ru, Zr, but only minor enrichment of rare earth elements. The Pu, possibly as Pu(V) according to EELS measurements, was dispersed within re-precipitated uranium oxide (identified as U3O8) nano-crystals between U(VI) secondary phases and the CSNF surface. The U, Pu, and Am enrichment was observed in the corrosion products with tests on different nuclear fuels. This may have implications for the long-term behavior of CSNF under storage in a geologic waste repository. Furthermore, there may be an increased potential for the generation of Pu-bearing colloids from this type of weathered CSNF. 相似文献