30 research outputs found
Thermal inactivation and conformational lock studies on glucose oxidase
In this study, the dissociative thermal inactivation
and conformational lock theories are applied for the
homodimeric enzyme glucose oxidase (GOD) in order to
analyze its structure. For this purpose, the rate of activity
reduction of glucose oxidase is studied at various temperatures
using b-D-glucose as the substrate by incubation of
enzyme at various temperatures in the wide range between
40 and 70 �C using UV–Vis spectrophotometry. It was
observed that in the two ranges of temperatures, the
enzyme has two different forms. In relatively low temperatures,
the enzyme is in its dimeric state and has normal
activity. In high temperatures, the activity almost disappears
and it aggregates. The above achievements are confirmed
by dynamic light scattering. The experimental
parameter ‘‘n’’ as the obvious number of conformational
locks at the dimer interface of glucose oxidase is obtained
by kinetic data, and the value is near to two. To confirm the
above results, the X-ray crystallography structure of the
enzyme, GOD (pdb, 1gal), was also studied. The secondary
and tertiary structures of the enzyme to track the thermal
inactivation were studied by circular dichroism and
fluorescence spectroscopy, respectively. We proposed a
mechanism model for thermal inactivation of GOD based
on the absence of the monomeric form of the enzyme by
circular dichroism and fluorescence spectroscopy
Aqueous Flow Reactor and Vapour-Assisted Synthesis of Aluminium Dicarboxylate Metal-Organic Frameworks with Tuneable Water Sorption Properties
Energy-efficient indoors temperature and humidity control can be realised by using the reversible adsorption and desorption of water in porous materials. Stable microporous aluminium-based metal-organic frameworks (MOFs) present promising water sorption properties for this goal. The development of synthesis routes that make use of available and affordable building blocks and avoid the use of organic solvents is crucial to advance this field. In this work, two scalable synthesis routes under mild reaction conditions were developed for aluminium-based MOFs: (1) in aqueous solutions using a continuous-flow reactor and (2) through the vapour-assisted conversion of solid precursors. Fumaric acid, its methylated analogue mesaconic acid, as well as mixtures of the two were used as linkers to obtain polymorph materials with tuneable water sorption properties. The synthesis conditions determine the crystal structure and either the MIL-53 or MIL-68 type structure with square-grid or kagome-grid topology, respectively, is formed. Fine-tuning resulted in new MOF materials thus far inaccessible through conventional synthesis routes. Furthermore, by varying the linker ratio, the water sorption properties can be continuously adjusted while retaining the sigmoidal isotherm shape advantageous for heat transformation and room climatisation applications
Eficácia do indoxacarb para o controle de pragas em hortaliças Efficacy of indoxacarb in the control of vegetable pests
A eficiência do indoxacarb foi avaliada no controle dos lepidópteros-pragas em hortaliças: Plutella xylostella (Lepidoptera: Yponeumatidae), Trichoplusia ni (Lepidoptera: Noctuidae), Neoleucinodes elegantalis (Lepidoptera: Pyralidae) e Helicoverpa zea (Lepidoptera: Noctuidae). Os experimentos foram conduzidos em três locais diferentes nas culturas do repolho e tomate. Os inseticidas utilizados foram indoxacarb (no tomate de 2,4 a 6,0 g i.a./100 L e no repolho de 18 a 42 g i.a./ha), esfenvalerate (apenas no tomate de 1,75 g i.a./100 L), metomil (no tomate na dose de 21,5 g i.a./100 L e no repolho a 172 g i.a./ha), deltametrina (apenas no repolho na dose de 6 g i.a./ha) e triflumuron (apenas no tomate na dose de 15 g i.a./100 L). Adotou-se o delineamento estatístico em blocos ao acaso com quatro repetições em todos os experimentos. Todas as doses avaliadas do produto indoxacarb apresentaram excelente desempenho no controle de P. xylostella e T. ni. Assim, a menor dose avaliada (18 g i.a./ha) pode ser recomendada para o controle dessas pragas. Todos os produtos avaliados alcançaram níveis de eficiência maiores que 80% no controle de H. zea na cultura do tomate. Indoxacarb foi tão eficiente quanto o produto padrão adotado (triflumuron). N. elegantalis foi eficientemente controlada pelos inseticidas avaliados após nove aplicações, sendo que indoxacarb pode ser recomendado na menor dose utilizada (2,4 g i.a./100 L).<br>The efficacy of indoxacarb was evaluated for controlling lepidopterous pests on vegetables: Plutella xylostella (Lepidoptera: Yponeumatidae), Trichoplusia ni (Lepidoptera: Noctuidae), Neoleucinodes elegantalis (Lepidoptera: Pyralidae), Helicoverpa zea (Lepidoptera: Noctuidae). The experiments were carried out at three different sites on cabbage and tomato crops. The utilized insecticides were indoxacarb (for tomato from 2.4 to 6.0 g a.i./100 L and for cabbage from 18 to 42 g i.a./ha), esfenvalerate (only for tomato at 1.75 g a.i./100 L), methomyl (for tomato at 21.5 g a.i./100 L and for cabbage at 172 g a.i./ha), deltamethrin (only for cabbage at 6 g a.i./ha) and triflumuron (only for tomato at 15 g a.i./100 L). The experiments were designed as randomized blocks with four replications. The results showed that all doses of indoxacarb presented excellent performance controlling P. xylostella and T. ni on cabbage. Therefore, the lowest tested dose should be used (18 g a.i./100 L). All products reached levels of efficacy higher than 80% for controlling H. zea on tomato crop. Indoxacarb was as efficient as the standard product triflumuron. N. elegantalis was efficiently controlled by the tested insecticides after nine applications and indoxacarb could be recommended at the lowest utilized dose (2.4 g a.i./100 L)
Investigation of nickel product structures developed during the gaseous reduction of solid nickel oxide
The product microstructures developed during the reduction of dense synthetic nickel oxide in H-2-N-2 and H-2-H2O mixtures between 300 A degrees C and 1000 A degrees C are reported. A number of distinctly different types of nickel product structures have been identified, namely, coarse fibrous nickel with fissures, fine porous nickel-planar interface, large porous nickel-irregular interface, and dense nickel layer. The influences of gas composition and temperature on the conditions for formation of these microstructures, and their evolution with temperature and time, have been systematically investigated. The condition for formation of the various microstructure types was summarized on morphology maps as functions of reducing gas partial pressure, thermodynamic driving force, and reaction temperature