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941.
Mallory Gobet Mohamed Mouaddab Nathalie Cayot Jean‐Marie Bonny Elisabeth Guichard Jean‐Luc Le Quéré Céline Moreau Loïc Foucat 《Magnetic resonance in chemistry : MRC》2009,47(4):307-312
23Na NMR spectroscopy has been used to study the effects of Na+ ion concentrations on the structure of 1% (w/w) iota‐carrageenan systems, a natural gelling polysaccharide used as a thickener in the food industry. Rheological and 23Na T1 relaxation time measurements revealed that gel formation correlates with decreases in ion mobility over the range of 0–3% (w/w) sodium content. 23Na single‐quantum (SQ) and double‐quantum‐filtered (DQF) NMR experiments performed on these systems provided evidence for a ‘bound’ sodium ion fraction in a specifically ordered environment. These results have allowed us to propose a model for the carrageenan gelation mechanism in the presence of Na+ ions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
942.
943.
B. W. Bailey F. C. Lo 《International journal of environmental analytical chemistry》2013,93(4):267-274
A procedure for the determination of submicrogram amounts of boron in aqueous solutions is described. The method is based on measuring the chemiluminescence of the molecular species BOx in either an air/hydrogen or air/acetylene flame. Detection limits obtained with these flames were 0.004 and 0.06 ppm, respectively. Potential interferences may be removed by ion-exchange chromatography. The procedure is applicable to the determination of boron in potable waters. 相似文献
944.
Synthesis and Antimycobacterial Evaluation on Arylsulfonyl and Arylcarbonyl Derivatives of Ofloxacin
Yeh‐Long Chen Yu‐Wen Chen We‐Fen Lo Chai‐Lin Kao Yu‐Shuan Liu Chen‐Wen Yao Chemg‐Chyi Tzeng 《中国化学会会志》2009,56(2):374-380
Four ofloxacin derivatives 3, 5, 6 , and 11 were found to exhibit > 90% inhibition on the growth of M. tuberculosis at a concentration of 6.25 μg/mL. Compounds 3, 5 and 11 have also exhibited a broad spectrum of antibacterial activities while 8‐fluoro‐3‐methyl‐9‐[4‐(4‐nitrophenylsulfonyl)piperazin‐1‐yl)‐6‐oxo‐2,3‐dihydro‐6H‐1‐oxo‐3a‐azaphenalene‐5‐carboxylic acid ( 6 ), which exhibited potent activity against the growth of TB with the MIC of 2.23 μg/mL and a selectivity index (SI) of > 14.80, was inactive against the growth of G(+)‐ and G(‐)‐bacteria. Selective anti‐TB activity was achieved by the introduction of an arylsulfonyl group at C‐7 piperazin‐4‐yl of N‐demethyl ofloxacin. Compound 6 is species‐specific, exhibiting no significant activity against the growth of bacterial species other than M. tuberculosis, which implied the possibility of developing new specific anti‐TB drug candidates without inducing cross resistance with other currently used antibacterial drugs. Structural optimization of 6 is on‐going. 相似文献
945.
946.
Laura Orsatti Federica Innocenti Paola Lo Surdo Fabio Talamo Gaetano Barbato 《Rapid communications in mass spectrometry : RCM》2009,23(17):2733-2740
The Phosphatase of Regenerating Liver‐3 (PRL‐3) is a cysteine‐based phosphatase (CBP) that is highly over‐expressed in liver metastasis in colorectal cancer and suspected to be involved in the progression from tumor to metastasis. During substrate‐specificity studies based on the screening of PRL‐3 phosphatase activity on several phosphorylated synthetic peptides, we observed a decrease in activity depending on sample aging and storage conditions. By liquid chromatography combined with selective alkylation and mass spectrometry, we found two main PRL‐3 inactivation pathways: a disulfide bond formation between the catalytic C104 and C49, blocking the enzyme in an inactive oxidized form, or the conversion of the catalytic C104 into glycine. We also found that the disulfide formation and the cysteine into glycine conversion are catalyzed by cations present in the sample after protein purification through a nickel column. By adding a cation chelator such as EDTA and de‐oxygenating the sample with argon, PRL‐3 phosphatase activity was preserved. These findings suggest that PRL‐3, like other CBPs, is sensitive to inactivation by catalytic cysteine oxidation and this has implications for future studies of its activity and specificity. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
947.
948.
In general relativity, according to Einstein, a gauge is related to the time dilation and the space contractions, and thus a physically realizable gauge should be unique for a given frame of reference. Since more than one metric solution for the same frame can produce the same deflection angle, this means that an invalid space-time metric can produce the correct deflection angle for a light ray. To demonstrate this with an unambiguous example, we consider a new extreme case that there is no space contraction in the radius direction while the conditions of asymptotic flatness and the requirement for gravitational red shifts are satisfied. This solution has a distinct characteristic of "space expansion" in the other directions. Nevertheless, it turns out that, in spite of requiring far more subtle calculations, the resulting deflection angle of a light ray is the same. An interesting property of this new solution is that its event horizon corresponds to an arbitrary integral constant. Thus, this calculation demonstrates beyond doubt that an unphysical solution can produce the correct first-order approximation of light bending. This makes it clear that there is a main difference between local effects such as the gravitational red shifts and the local light speeds, which are not gauge invariant, and integrated effects such as the bending of light, which can be (restricted) gauge invariant. 相似文献
949.
Law Kin-Ho Leung Yun-Chung Lawford Hugh Chua Hong Lo Wai-Hung Yu Peter Hoifu 《Applied biochemistry and biotechnology》2001,91(1-9):515-524
Plastic wastes are considered to be severe environmental contaminants causing waste disposal problems. Widespread use of biodegradable
plastics is one of the solutions, but it is limited by high production cost. Biologic wastewater treatment generates large
quantities of biomass as activated sludge. Only a few reports focus on the potential of utilizing resident Bacillus species from activated sludge in polyhydroxbutyrate (PHB) production as well as the production of PHB from food wastes. They
have attractive properties such as short generation time, absence of endotoxins, and secretion of both amylases and proteinases
that can well utilize food wastes for nutrients, which can further reduce the cost of production of polyhydroxyalkanoates
(PHAs). Two PHA-producing strains, HF-1 and HF-2, were isolated from activated sludge. HF-1 outperfomed HF-2 in terms of growth
and PHB production in hydrolyzed soy and malt wastes. The isolated bacteria was characterized by DNA sequence alignment. Cell
extracts of HF-1 were also compared to Bacillus megaterium cell extracts on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The biopolymers accumulated were analyzed by
gas chromatography, nuclear magnetic resonance, and Fourier transform infrared methods. 相似文献
950.
A. Saber P. Mazzoldi G. De Marchi S. Lo Russo G. Mattei 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(2):235-241
We examine the critical behavior of a magnetic superlattice which made up of two magnetic materials, A and B. Using the effective field theory with a probability distribution technique that accounts for the single-site spin correlation,
we derive the analytical equation for the Curie temperature of the superlattice which alternates as ABAB...AB. The dependence of the Curie temperature on the interface coupling strength Jab and the layer number of the finite superlattice was calculated. The effects of the surface modification are also studied.
Received 2 March 2001 相似文献