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181.
Amud AE da Silva GR Tardioli PW Soares CM Moraes FF Zanin GM 《Applied biochemistry and biotechnology》2008,146(1-3):189-201
Thermoanaerobacter cyclomaltodextrin glucanotransferase (CGTase) was immobilized using different supports and immobilization methods to study
the effect on activity recovery. The enzyme covalently attached into glyoxyl-silica showed low activity recovery of 1.5%.
The hydrophobic adsorption of the enzyme on Octadecyl-Sepabeads yielded also low activity recovery, 3.83%, and the enzyme
could easily leak from the support at low ionic strength, although the immobilization yield was satisfactory, approximately
76%. The CGTase encapsulated in a sol–gel matrix gave an activity recovery of 6.94% and maximum cyclization activity at 60
°C, at pH 6.0. The half-time life at 60 °C, pH 6.0, in the presence of substrate was 100 min, which was lower than that of
the free enzyme. The best activity recovery in this work (6.94%) is approximately five times smaller than that obtained previously
using glyoxyl-agarose as support and covalent immobilization. Thus, the best support and method we tested so far for immobilization
of CGTase is covalent attachment on glyoxyl-agarose. 相似文献
182.
The development of a highly sensitive sensor for oxygen is proposed using a glassy carbon (GC) electrode modified with alternated layers of iron(II) tetrasulfonated phthalocyanine (FeTsPc) and iron(III) tetra-(N-methyl-pyridyl)-porphyrin (FeT4MPyP). The modified electrode showed excellent catalytic activity for the oxygen reduction. The reduction potential of the oxygen was shifted about 330 mV toward less negative values with this modified electrode, presenting a peak current much higher than those observed on a bare GC electrode. Cyclic voltammetry and rotating disk electrode (RDE) experiments indicated that the oxygen reduction reaction involves 4 electrons with a heterogenous rate constant (kobs) of 3 × 105 mol−1 L s−1. A linear response range from 0.2 up to 6.4 mg L−1, with a sensitivity of 4.12 μA L mg−1 (or 20.65 μA cm−2 L mg−1) and a detection limit of 0.06 mg L−1 were obtained with this sensor. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation (R.S.D.) was 2.0% for 10 measurements of a solution of 6.4 mg L−1 oxygen. The sensor was applied to determine oxygen in pond and tap water samples showing to be a promising tool for this purpose. 相似文献
183.
Abraham F. Jalbout Flavio Contreras‐Torres R. Del Castillo 《International journal of quantum chemistry》2008,108(3):567-575
We have previously computed a set of hypothetical molecular surfaces, which formed charge pockets that were capable of excess electron entrapment. These charge pockets arose due to the fact that the molecular surfaces possessed an extended network of OH groups on one side of the surface and hydrogen atoms on the opposite side. The uneven distribution of the OH groups coupled to the partial positive charge of the hydrogen atoms caused electrons to be attracted to the surface. In the present investigation we will consider the ability of the hydrogen cyanide (HCN)‐water complex in stabilizing excess electrons on molecular surfaces. The computed vertical detachment energy (VDE) values are high, suggesting anion stability. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
184.
Jalbout AF Contreras-Torres FF Pérez LA Garzón IL 《The journal of physical chemistry. A》2008,112(3):353-357
In this work, we have explored new stable structures of the Au32Z (Z = +1, 0, -1) clusters. Theoretical calculations using density functional theory within the generalized-gradient approximation were performed. Our results show that, in the anion state (Au32-), low-symmetry (disordered) structures are preferred over the caged fullerene-like isomer. In addition, the cationic cluster (Au32+) also exhibits a disordered low-symmetry structure as its lowest energy configuration, but it is much closer in energy to the fullerene-like isomer. These results, obtained at T = 0 K, indicate that disordered structures for the Au32- and Au32+ clusters may be detected not only at room temperature, as was experimentally verified for the Au32- one, but also at much lower temperatures. 相似文献
185.
We present a novel algorithm for modeling electrical wave propagation in anatomical models of the heart. The algorithm uses a phase-field approach that represents the boundaries between the heart muscle and the surrounding medium as a spatially diffuse interface of finite thickness. The chief advantage of this method is to automatically handle the boundary conditions of the voltage in complex geometries without the need to track the location of these boundaries explicitly. The algorithm is shown to converge accurately in nontrivial test geometries with no-flux (zero normal current) boundary conditions as the width of the diffuse interface becomes small compared to the width of the cardiac action potential wavefront. Moreover, the method is illustrated for anatomically realistic models of isolated rabbit and canine ventricles as well as human atria. 相似文献
186.
Florentina Golgovici Alexandru Pumnea Aurora Petica Adrian Cristian Manea Oana Brincoveanu Marius Enachescu Liana Anicai 《Chemical Papers》2018,72(8):1889-1903
In the case of hydrogen production involving seawater electrolysis, one of the main targets is to develop more active cathodic materials, to optimize the efficiency of hydrogen evolution reaction (HER) and, by doing so, enhance the overall energy efficiency of electrolysis. Thus, to develop suitable HER electrocatalysts either an increase of the electrode active surface area or a design of a material having high intrinsic catalytic activity should be taken into consideration, both of them decreasing the HER overpotential. In the present work, various Ni–Mo alloy nanostructures (10–40 wt% Mo) have been prepared involving electrochemical deposition from aqueous and deep eutectic solvent (DES)-based electrolytes as potential cathodic materials suitable for hydrogen evolution reaction during water electrolysis. The electrocatalytic activity of the obtained layers has been investigated using real seawater electrolyte. The determined Tafel slopes suggested that the electrodeposited Ni–Mo alloy coatings follow an HER mechanism controlled by the Volmer reaction step. The EIS results indicated that the use of choline chloride-based ionic liquids as electrolytes facilitated Ni–Mo alloy coatings showing a significant increase in surface roughness. Studies of the intrinsic activity showed that the main contribution towards the apparent activity comes from the increase of the real surface area, although a slight increase of the intrinsic electrocatalytic activity in the case of Ni–Mo alloy coatings electrodeposited on Ni foam was also noticed. These results showed that Ni–Mo alloy coatings electrodeposited from the novel electrolytes based on choline chloride–urea–citric acid ternary mixtures associated with a porous substrate may represent a promising technological approach to build cathodic materials suitable for seawater electrolysis. 相似文献
187.
In this paper we present exact results for the critical exponents of interacting self-avoiding walks with ends at a linear boundary. Effective interactions are mediated by vacancies, correlated and uncorrelated, on the dual lattice. By choosing different boundary conditions, several ordinary and special regimes can be described in terms of clusters geometry and of critical and lowtemperature properties of the
model. In particular, the problem of boundary exponents at the -point is fully solved, and implications for-point universality are discussed. The surface crossover exponent at the special transition of noninteracting self-avoiding walks is also interpreted in terms of percolation dimensions. 相似文献
188.
Maria Rosaria Iesce Rosalia Sferruzza Flavio Cermola Marina DellaGreca 《Helvetica chimica acta》2016,99(4):296-301
Furanyl alcohols react with arenes by a variant of the Friedel–Crafts reaction to give benzyl furans with fairly satisfying yields. The reaction is mediated by Tf2O and occurs with reduced times in the presence of Ph3PO. Some prepared compounds exhibit a lignan‐like backbone. 相似文献
189.
Press‐Printed Conductive Carbon Black Nanoparticle Films for Molecular Detection at the Microscale 下载免费PDF全文
Flavio Della Pelle Dr. Luis Vázquez Prof. Michele Del Carlo Prof. Manuel Sergi Prof. Dario Compagnone Prof. Alberto Escarpa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12761-12766
Carbon black nanoparticle (CBNP) press‐transferred film‐based transducers for the molecular detection at the microscale level were proposed for the first time. Current‐sensing atomic force microscopy (CS‐AFM) revealed that the CBNP films were effectively press‐transferred, retaining their good conductivity. A significant correlation between the morphology and the resistance was observed. The highest resistance was localized at the top of the press‐transferred film protrusions, whereas low values are usually obtained at the deep crevices or grooves. The amount of press‐transferred CBNPs is the key parameter to obtain films with improved conductivity, which is in good agreement with the electrochemical response. In addition, the conductivity of such optimum films was not only Ohmic; in fact, tunneling/hopping contributions were observed, as assessed by CS‐AFM. The CBNP films acted as exclusive electrochemical transducers as evidenced by using two classes of molecules, that is, neurotransmitters and environmental organic contaminants. These results revealed the potential of these CBNP press‐transferred films for providing new options in microfluidics and other related micro‐ and nanochemistry applications. 相似文献
190.