Search results for " hydrolysis"
showing 10 items of 142 documents
Molecular Mechanism of ATP Hydrolysis in an ABC Transporter
2018
Hydrolysis of nucleoside triphosphate (NTP) plays a key role for the function of many biomolecular systems. However, the chemistry of the catalytic reaction in terms of an atomic-level understanding of the structural, dynamic, and free energy changes associated with it often remains unknown. Here, we report the molecular mechanism of adenosine triphosphate (ATP) hydrolysis in the ATP-binding cassette (ABC) transporter BtuCD-F. Free energy profiles obtained from hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations show that the hydrolysis reaction proceeds in a stepwise manner. First, nucleophilic attack of an activated lytic water molecule at the ATP γ-…
Metabolic detoxification: implications for thresholds.
2000
The fact that chemical carcinogenesis involves single, isolated, essentially irreversible molecular events as discrete steps, several of which must occur in a row to finally culminate in the development of a malignancy, rather suggests that an absolute threshold for chemical carcinogens may not exist. However, practical thresholds may exist due to saturable pathways involved in the metabolic processing, especially in the metabolic inactivation, of such compounds. An important example for such a pathway is the enzymatic hydrolysis of epoxides via epoxide hydrolases, a group of enzymes for which the catalytic mechanism has recently been established. These enzymes convert their substrates via…
Multifarious pretreatment strategies for the lignocellulosic substrates for the generation of renewable and sustainable biofuels: A review
2020
Abstract Currently major part of the world’s energy requirements is fulfilled by fossil resources. Severe economic and environmental problems along with their limited resources are still a major issue. Long-term environmental and commercial concern has focussed into huge research in the past decades to replace fossil fuels with renewable sources of energy. The main focus of energy research is lignocellulosic substrates, which seems to be the best for energy application due to easily availability, cost-effective and environment favourable production process. Therefore, lignocellulosic materials provide economical, environmental and energetic benefits with an alternative to traditional or hig…
Spectrophotometric determination of ethiofencarb in waters by reaction with p-aminophenol
1993
An automatized procedure has been developed for the spectrophotometric determination of ethiofencarb in water by reaction with p-aminophenol after alkaline hydrolysis to obtain the corresponding phenol sulphone. The hydrolyzed samples are continuously introduced into different manifolds at the same time as 300 mg/l p-aminophenol, 0.004 mol/l KIO4 and 0.04 mol/l NaOH solutions. The absorbance is measured at 638 nm after a reaction time of 6 min in stop flow. This absorbance band corresponds to the indo dye obtained from the reaction between the phenol sulphone of ethiofencarb and the quinoneimine form of the p-aminophenol and it permits a matrix-free spectrophotometric determination of ethio…
Dioxouranium(VI) hydrolysis at 75 and 100°C in 3.6 molkg-1 LiClO4
2008
This work concerns the acidic properties of uranyl ion UO22+ at 75 and 100 °C in 3.6 molal (molkg-1 solvent) LiClO4 aqueous medium. The investigation was carried out by a coulometric-potentiometric technique. Direct and reverse acid base titrations were carried out in order to check the achievement of actual equilibrium conditions. Moreover, in order to reveal oversaturation conditions, a further check was carried out on clean saturated hydrolyzed solutions.
Ein neuer weg zur herstellung von oligomeren aus acryl- und vinylverbindungen; modell einer matrizenreaktion
1966
In einer Reihe vorangehender Untersuchungen wurde die Herstellung molekulareinheitlicher, phenolischer Mehrkernverbindungen beschrieben. Sie besitzen je Phenolbaustein eine phenolische Hydroxylgruppe, wie systematisch untersuchte Acylierungen sowie Methylierung und Arylierung dieser Mehrkernverbindungen zeigen. In der vorliegenden Mitteilung wurde bei einer Zwei- und Dreikernverbindung an den phenolischen Hydroxylgruppen mit Acrylsaurechlorid umgesetzt, so das die entstandenen Verbindungen so viele polymerisationsfahige Reste wie phenolische Bausteine besasen. Die Polymerisation der Acrylsaurederivate in sehr groser Verdunnung gab oligomere Leiterverbindungen, die durch alkalische Hydrolyse…
Nested MWC model describes hydrolysis of GroEL without assuming negative cooperativity in binding
2002
Folding assistance and ATPase activity of GroEL are based on the existence of different conformations. In order to characterise these conformations, published data on steady state ATPase activity in the absence of GroES were reanalysed simultaneously in terms of the Nested MWC model. This model is a hierarchical extension of the symmetry-model of Monod et al. [J. Mol. Biol. 12 (1965) 88]. An unique set of GroEL specific parameters was obtained. This set was supported by comparison of predictions arising from this set of values with experimental data for hydrolysis of ATP in the presence of ADP and ATPgammaS, binding of ATPgammaS and ADP to GroEL in the absence of ATP, and binding of ATP as …
Control of adenine nucleotide metabolism and glycolysis in vertebrate skeletal muscle during exercise.
1996
The turnover of adenosine triphosphate (ATP) in vertebrate skeletal muscle can increase more than a hundredfold during high-intensity exercise, while the content of ATP in muscle may remain virtually unchanged. This requires that the rates of ATP hydrolysis and ATP synthesis are exactly balanced despite large fluctuations in reaction rates. ATP is regenerated initially at the expense of phosphocreatine (PCr) and then mainly through glycolysis from muscle glycogen. The increased ATP turnover in contracting muscle will cause an increase in the contents of adenosine diphosphate (ADP), adenosine monophosphate (AMP) and inorganic phosphate (P(i)), metabolites that are substrates and activators o…
Clean analytical method for the determination of propoxur
1995
Abstract A method has been developed for the determination of propoxur, a carbamate pesticide, by means of its reaction with p-aminophenol (PAP). The method involves the reaction, in the presence of KIO4, between the quinoneimine form of PAP and the deprotonated form of 2-isopropoxyphenol, obtained by the alkaline hydrolysis of propoxur, to provide an indophenol dye which absorbs at 600 nm. The analysis is carried out in a flow system and, after the measurement step, the waste, the reaction product and the unreacted derivatising agent is detoxified in a UV-irradiated coil placed after the measurement flow-cell and after mixing the waste with a TiO2(anatase) catalyst slurry, which can be reu…
Anatase nanoparticles boundaries resulting from titanium tetrachloride hydrolysis
2017
An important factor that governs solar energy transformation into electrical or chemical energy, when using nanoparticles-based devices, is the spatial location of traps limiting electron transport. Evidences have been presented indicating that the electron diffusion is strongly influenced by nanoparticle boundaries, whose characteristics depend on the particles preparation. In the present work we have studied the role of hydrated excess proton structures in the formation of anatase nanoparticles boundaries in samples prepared by TiCl4 hydrolysis at low temperature and strong acidic conditions. The samples, constituted by anatase nanocrystals but, mainly, by amorphous titania, are studied b…