排序方式: 共有86条查询结果,搜索用时 31 毫秒
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Chen X Luais E Darwish N Ciampi S Thordarson P Gooding JJ 《Langmuir : the ACS journal of surfaces and colloids》2012,28(25):9487-9495
The preparation of self-assembled monolayers (SAMs) of organophosphonic acids on indium tin oxide (ITO) surfaces from different solvents (triethylamine, ethyl ether, tetrahydofuran (THF), pyridine, acetone, methanol, acetonitrile, dimethyl sulfoxide (DMSO), or water) has been performed with some significant differences observed. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and contact angle measurement demonstrated that the quality of SAMs depends critically on the choice of solvents. Higher density, more stable monolayers were formed from solvents with low dielectric constants and weak interactions with the ITO. It was concluded low dielectric solvents that were inert to the ITO gave monolayers that were more stable with a higher density of surface bound molecules because higher dielectric constant solvents and solvents that coordinate with the surface disrupted SAM formation. 相似文献
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Monia Blibech Raoudha Ellouz Ghorbel Ines Fakhfakh Patricia Ntarima Katheleen Piens Abir Ben Bacha Semia Ellouz Chaabouni 《Applied biochemistry and biotechnology》2010,160(4):1227-1240
The highest β-mannanase activity was produced by Penicillium occitanis Pol6 on flour of carob seed, whereas starch-containing medium gave lower enzymes titles. The low molecular weight enzyme
was purified to homogeneity by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography procedures.
The purified β-mannanase (ManIII) has been identified as a glycoprotein (carbohydrate content 5%) with an apparent molecular
mass of 18 kDa. It was active at 40 °C and pH 4.0. It was stable for 30 min at 70 °C and has a broad pH stability (2.0–12.0).
ManIII showed K
m, V
max, and K
cat values of 17.94 mg/ml, 93.52 U/mg, and 28.13 s−1 with locust bean gum as substrate, respectively. It was inhibited by mannose with a K
I of 0.610−3 mg/ml. ManIII was activated by CuSO4 and CaCl2 (2.5 mM). However, in presence of 2.5 mM Co2+, its activity dropped to 60% of the initial activity. Both N-terminal and internal amino acid sequences of ManIII presented
no homology with mannanases of glycosides hydrolases. During incubation with locust bean gum and Ivory nut mannan, the enzyme
released mainly mannotetraose, mannotriose, and mannobiose. 相似文献
54.
H. Raissi Abraham F. Jalbout B. Abbasi F. Fazli F. Farzad E. Nadim Aned de Leon 《International journal of quantum chemistry》2010,110(4):893-901
The molecular structure and intramolecular hydrogen bond energy of 18 conformers of 3‐imino‐propenyl‐amine were investigated at MP2 and B3LYP levels of theory using the standard 6‐311++G** basis set. The atom in molecules or AIM theory of Bader, which is based on the topological properties of the electron density (ρ), was used additionally and the natural bond orbital (NBO) analysis was also carried out. Furthermore calculations for all possible conformations of 3‐imino‐propenyl‐amin in water solution were also carried out at B3LYP/6‐311++G** and MP2/6‐311++G** levels of theory. The calculated geometrical parameters and conformational analyses in gas phase and water solution show that the imine–amine conformers of this compound are more stable than the other conformers. B3LYP method predicts the IMA‐1 as global minimum. This stability is mainly due to the formation of a strong N? H···N intramolecular hydrogen bond, which is assisted by π‐electrons resonance, and this π‐electrons are established by NH2 functional group. Hydrogen bond energies for all conformers of 3‐imino‐propenyl‐amine were obtained from the related rotamers methods. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
55.
Ciampi S James M Darwish N Luais E Guan B Harper JB Gooding JJ 《Physical chemistry chemical physics : PCCP》2011,13(34):15624-15632
A novel method to prepare redox monolayers on silicon electrodes has been developed that employs Cu(I)-catalyzed oxidative acetylenic coupling reactions for molecular electronic type applications. As the first case study, ethynylferrocene was covalently immobilized onto an acetylene-terminated monolayer on a Si(100) surface to give a 1,3-diyne (C≡C-C≡C-) linked redox assembly. The derivatization process requires no protection/de-protection steps, nor activation procedures. The effect of the conjugated diyne linkage on the rate of electron transfer between tethered ferrocenyl units and the silicon electrode is benchmarked against well-established "click" products (i.e. 1,2,3-triazole linkage). The surfaces, after each step, are characterized thoroughly using X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The coupling chemistry provides a useful strategy for functionalizing silicon surfaces and contributes to an expanding repertoire of wet chemistry routes for the functionalization of solid substrates. 相似文献
56.
Investigation of the Antifouling Properties of Phenyl Phosphorylcholine‐Based Modified Gold Surfaces
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Maryam Parviz Nadim Darwish Muhammad Tanzirul Alam Stephen G. Parker Simone Ciampi J. Justin Gooding 《Electroanalysis》2014,26(7):1471-1480
Low impedance, antifouling coatings on gold electrodes based on three new zwitterionic phenyl phosphorylcholine (PPC)‐based layers namely 1) reductively adsorbed PPC diazonium salt, 2) dithiocarbamate PPC SAM and 3) lipoamide PPC SAM (PPC coupled to α‐lipoic acid) were evaluated. The layers were assessed for their ability to limit nonspecific adsorption of proteins to electrode surface with some significant differences observed compared with previously studied PPC diazonium salts reductively adsorbed on glassy carbon. Fluorescence microscopy and electrochemical impedance spectroscopy results suggest that protein adsorption is sensitive to the difference in the structure of the PPC molecules and the charge neutrality of the layers. The lipoamide PPC SAM was shown to be the most effective at resisting nonspecific protein adsorption and this layer was as effective as the ‘gold standard’ of oligo(ethylene oxide) SAMs on gold and PPC diazonium salts reductively adsorbed on glassy carbon. 相似文献
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Modeling the Enhanced Bioremediation of Organic Contaminants in Pyrite-containing Aquifers 总被引:1,自引:0,他引:1
The bioremediation of organic contaminants in the subsurface is strongly influenced by the existing geochemical environment.
In this study a coupled reactive transport and geochemical model is developed for the simulation of enhanced bioremediation
of organic contamination in the presence of pyrite. The two-dimensional model allows for the simulation of both kinetically
defined as well as geochemical equilibrium reactions. The model is applied to a hypothetical pyrite-containing aquifer contaminated
with petroleum hydrocarbons. Oxygen injected into the aquifer to enhance contaminant biodegradation reacts with pyrite resulting
in reduced oxygen availability, acidification of the subsurface environment and, subsequently, the inadvertent inhibition
of the microbial activity. The reactive transport and geochemical model is used to quantify these processes. The dominance
of the various chemical reactions and the sensitivity of the biodegradation on pyrite content are evaluated. Through groundwater
pH manipulation, the interference of pyrite with the intended remedial action is partially mitigated. It is shown that when
oxygen availability is a limiting factor, the optimal pH that would maximize hydrocarbon degradation may significantly differ
from the pH value that maximizes bacterial activity. 相似文献
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Mohamed Slim Abbes Moez Trigui Fakher Chaari Tahar Fakhfakh Mohamed Haddar 《European Journal of Mechanics - A/Solids》2010,29(5):887-896
In this paper a novel approach for modelling a spur gear system using finite element method combined with elastic foundation theory is developed. The pinion is modelled by shaft finite element and the wheel by a three-dimensional finite element. Elastic foundation is utilized to model the gearmesh. The modal analysis showed the presence of lower natural frequency for thin rimmed gear cases susceptible to be excited by the operating running condition. The transmission error is affected by the wheel shape and by the presence of lower natural frequencies. Eccentricity error and tooth crack are also modelled to observe their influence on the dynamics behaviour of the system. It was found that they are responsible of the apparition of an amplitude modulation. 相似文献
60.
A total of twelve novel enantiomerically pure tetra-carbohydrazide cyclophane macrocycles have been synthesised in quantitative yields by reacting chiral (4R,5R)- and (4S,5S)-1,3-dioxolane-4,5-dicarbohydrazides with aromatic bis-aldehydes in a [2 + 2]-cyclocondensation reaction. The compounds show a dynamic behaviour in solution, which has been rationalized in terms of an unprecedented conformational interconversion between two conformers one stabilised by intramolecular hydrogen bonding and π-π stacking interactions. 相似文献