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排序方式: 共有150条查询结果,搜索用时 93 毫秒
11.
Tianfang Wang T. T. Nha Tran Denis Scanlon Hayley J. Andreazza Andrew D. Abell John H. Bowie 《Rapid communications in mass spectrometry : RCM》2011,25(18):2649-2656
It has been shown previously that [M–H]– anions of small peptides containing two phosphate residues undergo cyclisation of the phosphate groups, following collision‐induced dissociation (CID), to form a characteristic singly charged anion A (H3P2O7–, m/z 177). In the present study it is shown that the precursor anions derived from the diphosphopeptides of caerin 1.1 [GLLSVLGSVAKHVLPHVVPVIAEHL(NH2)] and frenatin 3 [GLMSVLGHAVGNVLGGLFKPKS(OH)] also form the characteristic product anion A (m/z 177). Both of the precursor peptides show random structures in water, but partial helices in membrane‐mimicking solvents [e.g. in d3‐trifluoroethanol/water (1:1)]. In both cases the diphosphopeptide precursor anions must have flexible conformations in order to allow approach of the phosphate groups with consequent formation of A: for example, the two pSer groups of 4,22‐diphosphofrenatin 3 are seventeen residues apart. Finally, CID tandem mass spectrometric (MS/MS) data from the [M–H]– anion of the model triphosphoSer‐containing peptide GpSGLGpSGLGpSGL(OH) show the presence of both product anions A (m/z 177) and D (m/z 257, H4P3O10–). Ab initio calculations at the HF/6‐31+G(d)//AM1 level of theory suggest that cyclisation of the three phosphate groups occurs by a stepwise cascade mechanism in an energetically favourable reaction (ΔG = ?245 kJ mol–1) with a maximum barrier of +123 kJ mol–1. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
12.
MD. Anwarul Hasan Carlos F. Lange Malcolm L. King 《ournal of non Newtonian Fluid Mechanics》2010,165(21-22):1431-1441
The effect of viscoelastic properties and surface tension of artificial mucus simulant samples on the size distribution and volume concentration of bioaerosol droplets generated during simulated coughing was investigated through in vitro experiments. The mucus simulant samples had viscoelastic properties in a similar range as those of real human airway mucus. The mucus simulant gels were prepared by mixing various proportions of 0.5–1.7% locust bean gum solution and 0.1 M sodium tetraborate (XLB) solution. Surface tension of one set of samples was varied by adding different amounts of SDS (sodium dodecyl sulfate) surfactant while the measurement of surface tension was performed using ADSA (axisymmetric drop shape analysis) method. The viscoelastic properties of the samples were measured using a Bohlin Gemini 200 HR (Malvern, UK) nano-rheometer with peltier plate assembly. An artificial cough machine was used to simulate human cough, generating aerosol droplets in a model trachea attached to the front of the cough machine. The size distribution and volume concentration of the droplets generated through simulated cough were measured using a laser diffraction particle sizer (SprayTec, Malvern, USA). The surface tension was found to have negligible effect on the characteristic of generated droplets within the range of this investigation. The experimental results showed a decrease in particle size as the samples changed from a viscous fluid type to a viscoelastic to an elastic solid type sample. The volume concentration also changed significantly as the viscoelasticity of the samples was varied. 相似文献
13.
M.?J.?SticklandEmail author T.?J.?Scanlon P.?Waddell J.?Fernandez-Francos E.?Blanco 《Experiments in fluids》2003,34(2):304-306
This paper describes the use of a rotating all-mirror image derotator system, high-speed video and particle image velocimetry
(PIV) to visualise and quantitatively examine the flow patterns between the blades of a centrifugal impeller. The flow field
relative to the moving centrifugal impeller is presented.
Published online: 13 December 2002 相似文献
14.
CdO has been studied for decades as a prototypical wide band gap transparent conducting oxide with excellent n-type ability. Despite this, uncertainty remains over the source of conductivity in CdO and over the lack of p-type CdO, despite its valence band maximum (VBM) being high with respect to other wide band gap oxides. In this article, we use screened hybrid DFT to study intrinsic defects and hydrogen impurities in CdO and identify for the first time the source of charge carriers in this system. We explain why the oxygen vacancy in CdO acts as a shallow donor and does not display negative-U behavior similar to all other wide band gap n-type oxides. We also demonstrate that p-type CdO is not achievable, as n-type defects dominate under all growth conditions. Lastly, we estimate theoretical doping limits and explain why CdO can be made transparent by a large Moss-Burstein shift caused by suitable n-type doping. 相似文献
15.
We show that NIP fields have no Artin-Schreier extension, and that simple fields have only a finite number of them. 相似文献
16.
Thomas Scanlon 《Journal of Number Theory》2002,97(1):10-25
We prove an analogue of the Manin-Mumford conjecture for Drinfeld modules of generic characteristic. 相似文献
17.
18.
Dr. Peiyu Ge Dr. Mohamad Hojeij Dr. Micheál D. Scanlon Prof. Hubert H. Girault 《Chemphyschem》2020,21(24):2630-2633
H2 may be evolved biphasically using a polarised liquid|liquid interface, acting as a “proton pump”, in combination with organic soluble metallocenes as electron donors. Sustainable H2 production requires methodologies to recycle the oxidised donor. Herein, the photo-recycling of decamethylferrocenium cations (DcMFc+) using aqueous core-shell semiconductor CdSe@CdS nanoparticles is presented. Negative polarisation of the liquid|liquid interface is required to extract DcMFc+ to the aqueous phase. This facilitates the efficient capture of electrons by DcMFc+ on the surface of the photo-excited CdSe@CdS nanoparticles, with hydrophobic DcMFc subsequently partitioning back to the organic phase and resetting the system. TiO2 (P25) and CdSe semiconductor nanoparticles failed to recycle DcMFc+ due to their lower conduction band energy levels. During photo-recycling, CdS (on CdSe) may be self-oxidised and photo-corrode, instead of water acting as the hole scavenger. 相似文献
19.
Transcellular diffusion across the absorptive epithelial cells (enterocytes) of the small intestine is the main route of absorption for most orally administered drugs. The process by which lipophilic compounds transverse the aqueous environment of the cytoplasm, however, remains poorly defined. In the present study, we have identified a structurally diverse group of lipophilic drugs that display low micromolar binding affinities for a cytosolic lipid-binding protein - intestinal fatty acid-binding protein (I-FABP). Binding to I-FABP significantly enhanced the transport of lipophilic drug molecules across a model membrane, and the degree of transport enhancement was related to both drug lipophilicity and I-FABP binding affinity. These data suggest that intracellular lipid-binding proteins such as I-FABP may enhance the membrane transport of lipophilic xenobiotics and facilitate drug access to the enterocyte cytoplasm and cytoplasmic organelles. 相似文献
20.
V. Leroy A. Strybulevych M. G. Scanlon J. H. Page 《The European physical journal. E, Soft matter》2009,29(1):123-130
We investigate, both experimentally and theoretically, the effect of coupling between resonant scatterers on the transmission
coefficient of a model system of isotropic scatterers. The model system consists of a monodisperse layer of bubbles, which
exhibit a strong monopole scattering resonance at low ultrasonic frequencies. The layer was a true 2D structure obtained by
injecting very monodisperse bubbles (with radius a ∼ 100 μm) into a yield-stress polymer gel. Even for a layer with a low concentration of bubbles (areal fraction, n
a
2 , of 10-20%, where n is the number of bubbles per unit area), the ultrasonic transmission was found to be significantly reduced by the presence
of bubbles (-20 to -50 dB) and showed a sharp minimum at a particular frequency. Interestingly, this frequency did not correspond
to the resonance frequency of the individual, isolated bubbles, but depended markedly on the concentration. This frequency
shift is an indication of strong coupling between the bubbles. We propose a simple model, based on a self-consistent relation,
which takes into account the coupling between the bubbles and gives good agreement with the measured transmission coefficient. 相似文献