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11.
Camacho C Matías JC Cao R Matos M Chico B Hernández J Longo MA Sanromán MA Villalonga R 《Langmuir : the ACS journal of surfaces and colloids》2008,24(15):7654-7657
A new sensor design is reported for the construction of an amperometric enzyme biosensor toward H (2)O(2). It was based in the supramolecular immobilization of alternating layers of horseradish peroxidase (either modified with 1-adamantane or beta-cyclodextrin-branched carboxymethylcellulose residues) on Au electrodes coated with polythiolated beta-cyclodextrin polymer. The analytical response of the electrodes, using 1 mM hydroquinone as an electrochemical mediator, increases when the number of enzyme layers increases. The biosensor having three enzyme layers showed a sensitivity of 720 microA/M cm (2) and a detection limit of 2 microM and retained 96% of its initial activity after 30 days of storage. The host-guest supramolecular nature of the immobilization method was confirmed by cyclic voltammetry. 相似文献
12.
Edward E. vila Asilo J. Mora Gerzon E. Delgado Belkis M. Ramírez Alí Bahsas Sonia Koteich 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(10):o759-o761
In the title compound, C7H13NO2·0.5H2O, cis‐4‐aminocyclohexanecarboxylic acid exists as a zwitterion and co‐crystallizes with water molecules in a 2:1 amino acid–water ratio. The cyclohexane ring adopts a chair conformation, with the carboxylate and ammonium groups in axial and equatorial positions, respectively. The basic motif in the crystal structure is a sandwich structure, formed by two amino acid units linked by head‐to‐tail hydrogen bonds. Hydrogen bonds of the type N+—H⋯O—C—O− link these motifs, forming helicoidally extended chains running along the c axis. The water molecule lies on a twofold axis and interacts with the chains by means of O—H⋯O hydrogen bonds. 相似文献
13.
Tekant Gözler Belkis Gözler Amarendra Patra John E. Leet Alan J. Freyer Maurice Shamma 《Tetrahedron》1984,40(7):1145-1150
Konyanin (), obtained from (Rutaceae), is the first known 1,4-dihydroarylnaphthalene lignan in which the lactone carbonyl is bonded to C-3 rather than to C-2. Detailed NMR spectral data have been complied for the accompanying lignans (-)-kusunokinin () and diphyllin (). 相似文献
14.
Conrado Camacho Juan C. Matías Belkis Chico Roberto Cao Leissy Gómez Benjamin K. Simpson Reynaldo Villalonga 《Electroanalysis》2007,19(24):2538-2542
Horseradish peroxidase, previously modified with 1‐adamantane moieties, was supramolecularly immobilized on gold electrodes coated with perthiolated β‐cyclodextrin. The functionalized electrode was employed for the construction of an amperometric biosensor device for hydrogen peroxide using 1 mM hydroquinone as electrochemical mediator. The biosensor exhibited a fast amperometric response (6 s) and a good linear response toward H2O2 concentration between 12 μM and 450 μM. The biosensor showed a sensitivity of 1.02 mA/M cm2, and a very low detection limit of 5 μM. The electrode retained 97% of its initial electrocatalytic activity after 30 days of storage at 4 0C in 50 mM sodium phosphate buffer, pH 7.0. 相似文献
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16.
Belkis Sulbarán Guillermo Toriz G. Graham Allan Gerald H. Pollack Ezequiel Delgado 《Cellulose (London, England)》2014,21(3):1143-1148
The dynamics of the development of solute exclusion zones produced by water in contact with various cellulosic surfaces are reported. The term “exclusion zone” (EZ) refers to the ordered water volume present immediately contiguous to hydrophilic surfaces. As such, three examples of cellulose-based films, i.e., cellophane, cellulose acetate with 0.94 degree of substitution (CA0.94) and cellulose acetate with 2.51 degree of substitution (CA2.51) were compared by exposure to sulfated-polystyrene microspheres (2 μm diameter) suspended in water. Zones that were not penetrated by the microspheres were observed in each case and measured by means of an optical microscope. The thickness of these exclusion zones adjacent to the cellulosic surfaces increased progressively with time and reached a maximum value of 190 μm after 1 h of exposure. Zone formation was influenced by roughness, crystallinity, and the degree of acetylation of the surfaces. For the cellulosic surfaces, the rougher the surface, the thicker was the EZ formed. Both the accessibility and availability of the hydroxyl groups on the cellulosic surfaces also influenced the thickness of the resultant EZ in the sequence, cellophane > CA0.94 > CA2.51. The surface of cellulose acetate with the greater substitution degree (CA2.51) produced the thinnest EZ. The diminution of the capacity of these cellulose derivatives to instigate water-molecule ordering is considered to be due to the hydrophobicity imparted by the acetyl group content. 相似文献
17.
Eliana M. Alhadeff Andréa M. Salgado Nei Pereira Jr. Belkis Valdman 《Applied biochemistry and biotechnology》2005,121(1-3):361-371
A sequential enzymatic double microreactor system with dilution line was developed for quantifying ethanol from gasohol mixtures,
using a colorimetric detection method, as a new proposal to the single micro reactor system used in previous work. Alcohol
oxidase (AOD) and horseradish peroxidase (HRP) immobilized on glass beads, one in each microreactor, were used with phenol
and 4-aminophenazone and the red-colored product was detected with a spectrophotometer at 555 nm. Good results were obtained
with the immobilization technique used for both AOD and HRP enzymes, with best retention efficiencies of 95.3 ± 2.3% and 63.2
± 7.0%, respectively. The two microreactors were used to analyze extracted ethanol from gasohol blends in the range 1–30 %
v/v (10.0–238.9 g ethanol/L), with and without an on-line dilution sampling line. A calibration curve was obtained in the
range 0.0034–0.087 g ethanol/L working with the on-line dilution integrated to the biosensor—FIA system proposed. The diluted
sample concentrations were also determined by gas chromatography (GC) and high-pressure liquid chromatography (HPLC) methods
and the results compared with the proposed sequential system measurements. The effect of the number of analysis performed
with the same system was also investigated. 相似文献
18.
Matthias HornYesim Hepuzer Yusuf YagciBelkiz Bilgin-Eran Undina CernencoValeria Harabagiu Mariana PintealaBogdan C Simionescu 《European Polymer Journal》2002,38(11):2197-2205
The synthesis of the first two liquid crystalline polysiloxanes bearing 3,6-diaryl-2,5-dihydropyrrolo-[3,4-c]pyrrole-1,4-dione units in their main chain are described. Investigations on their thermotropic phase behaviour by polarising microscopy reveal nematic or smectic enantiotropic phases, respectively. 相似文献
19.
Jines E. Contreras Belkis Ramírez V. Graciela Díaz de Delgado 《Journal of chemical crystallography》1997,27(7):391-395
[Cd(C5H4O4)(OH2)2] (1), crystallizes in the monoclinic system, space groupP21/n, with lattice parametersa=7.323(2),b=16.028(6),c=7.202(2) Å, β=113.11(1)°, andZ=4. The Cd atom coordinates to seven oxygens in a monocapped trigonal antiprism fashion. The antiprisms share one vertex to form chains which run approximately parallel to thec axis. The itaconate ligands link the chains to form layers which stack along theb axis. 相似文献
20.
Zusammenfassung Es wurden zwei neue Formazane, und zwar 1-Phenyl-5-(2-carboxyphenyl)-3-(3-methyl-2-chinoxalyl)-formazan und 1-Phenyl-5-(2-carboxyphenyl)-3-(3-methyl-2-chinolyl)-formazan synthetisiert. Diese Verbindungen bilden mit Uranyl-, Kobalt-und Nickelionen gut definierte Komplexe. Bei ihren Uran- und Kobaltkomplexen wurde ein Metall/Formazan-Verhältnis von 12, bei den Nickelkomplexen dagegen 11 festgestellt. Außerdem wurden Kobalt- und Nickelkomplexe des 3-Methylchinoxalin-2-aldehyd-o-hydroxy-anils mit einem Metall/Formazan-Verhältnis von 12 dargestellt.
Teil der DissertationB. Ocakcioglu, Univ. Istanbul 1969. 相似文献
Metal complexes of heterocyclic substituted formazans and azomethines
Two new formazans, 1-phenyl-5-(2-carboxyphenyl)-3-(3-methyl-2-quinoxalyl)-formazan and 1-phenyl-5-(2-carboxyphenyl)-3-(3-methyl-2-quinolyl)-formazan have been synthesized. These compounds form well defined complexes with uranyl, cobalt and nickel ions. The ratio of metal/formazan in uranium and cobalt complexes is 12, in nickel complexes 11. Besides, cobalt and nickel complexes of 3-methyl-quinoxaline-aldehyde-o-hydroxy-anil were synthesized with a metal/azomethine ratio of 12.
Teil der DissertationB. Ocakcioglu, Univ. Istanbul 1969. 相似文献