Search results for " hydrolysis"

Hydrolysis of Phosphotriesters: A Theoretical Analysis of the Enzymatic and Solution Mechanisms

2012

A theoretical study on the alkaline hydrolysis of paraoxon, one of the most popular organophosphorus pesticides, in aqueous solution and in the active site of Pseudomonas diminuta phosphotriesterase (PTE) is presented. Simulations by means of hybrid quantum mechanics/molecular mechanics (QM/MM) potentials show that the hydrolysis of paraoxon takes place through an A(N)D(N) or associative mechanism both in solution and in the active site of PTE. The results correctly reproduce the magnitude of the activation free energies and can be used to rationalize the observed kinetic isotope effects (KIEs) for the hydrolysis of paraoxon in both media. Enzymatic hydrolysis of O,O-diethyl p-chlorophenyl …

On the Reaction of 3-Bromo-2-nitrobenzo[b]thiophene 13C-Labeled at C-2 with 3-(Trifluoromethyl)aniline:  A Preliminary Insight into a Nucleophilic Su…

1997

The results of the title reaction have furnished proofs against a rearrangement of the carbon-atom skeleton and for a nitro group shift in the relevant nucleophilic substitution.

Kti12, a PSTK-like tRNA dependent ATPase essential for tRNA modification by Elongator

2019

Abstract Posttranscriptional RNA modifications occur in all domains of life. Modifications of anticodon bases are of particular importance for ribosomal decoding and proteome homeostasis. The Elongator complex modifies uridines in the wobble position and is highly conserved in eukaryotes. Despite recent insights into Elongator's architecture, the structure and function of its regulatory factor Kti12 have remained elusive. Here, we present the crystal structure of Kti12′s nucleotide hydrolase domain trapped in a transition state of ATP hydrolysis. The structure reveals striking similarities to an O-phosphoseryl-tRNA kinase involved in the selenocysteine pathway. Both proteins employ similar …

ChemInform Abstract: Synthesis and Reactivity of New β-Enamino Acid Derivatives: A Simple and General Approach to β-Enamino Esters and Thioesters.

2010

A new strategy has been developed for the synthesis of several β-enamino acid derivatives. N,N‘-Carbonyldiimidazole has been used as C-acylating agent of methyl ketimines, providing a direct and simple route to new β-enamino carbonyl imidazole derivatives 2. These derivatives 2 were cleanly and efficiently transformed into β-enamino esters 4 (X = O) and thioesters 4 (X = S) by reaction with a great variety of alcohols and thiols, including tertiary ones. Alternative and complementary routes to compounds 4 were also investigated. In addition, β-keto esters 6 have been obtained by mild acid hydrolysis of β-enamino esters 4.

Reactivity of cellulose during hydrothermal carbonization of lignocellulosic biomass

2020

Abstract Hydrothermal carbonization (HTC) of pure cellulose (CE) and birchwood (BW) samples was carried out at temperatures between 160 and 280 °C, 0.5 h residence time and biomass-to-water ratio 1:5, to investigate the reactivity of cellulose in lignocellulosic biomass. Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) showed that the CE samples remained unaltered at temperatures up to 220 °C, but were significantly decomposed at 230 °C producing a thermal recalcitrant aromatic and high energy-dense material. FTIR showed that dehydration and aromatization reactions occurred at temperature equal or higher than 230 °C for the CE samples while a similar incre…

Preparation and Photoactivity of Rutile Obtained by Hydrolysis of TiCl4

2005

Identification of bound alcohols in soil humic acids by gas chromatography-mass spectrometry

2000

International audience; Humic acids are complex, partly macromolecular, yellow-brownish substances occurring in soils, waters and sediments. In order to shed some light on their molecular structure, crop humic acids were cleaved by alkaline hydrolysis (KOH). The products were fractionated by thin layer chromatography to give mono-alcohols which were analysed as acetate derivatives by gas chromatography coupled to mass spectrometry. Linear alcohols, sterols, stanols and plant-derived triterpenoid alcohols were identified by co-injection of pure standards and by comparison with literature data. These findings imply that alcohols could have been incorporated into the humic matrix by esterifica…

Modelling hydrolysis: Simultaneous versus sequential biodegradation of the hydrolysable fractions

2018

Hydrolysis is considered the limiting step during solid waste anaerobic digestion (including co-digestion of sludge and biosolids). Mechanisms of hydrolysis are mechanistically not well understood with detrimental impact on model predictive capability. The common approach to multiple substrates is to consider simultaneous degradation of the substrates. This may not have the capacity to separate the different kinetics. Sequential degradation of substrates is theoretically supported by microbial capacity and the composite nature of substrates (bioaccessibility concept). However, this has not been experimentally assessed. Sequential chemical fractionation has been successfully used to define i…

Photocrosslinking of dextran and polyaspartamide derivatives: a combination suitable for colon-specific drug delivery.

2007

Abstract The aim of this study was to prepare and characterize novel hydrogels with polysaccharide–polyaminoacid structure, able to undergo an enzymatic hydrolysis in the colon and potentially useful for treating inflammatory bowel diseases (IBD). Starting materials were methacrylated dextran (DEX-MA) and methacrylated α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHM). These polymers were photocrosslinked by exposure of their aqueous solutions at 313 nm without photoinitiators. Different samples, shaped as microparticles, were obtained as a function of polymer concentration and irradiation time. FT-IR analysis confirmed the occurrence of a co-crosslinking between DEX-MA and PHM in all exper…

OATS AND FAT-FREE MILK BASED FUNCTIONAL FOOD PRODUCT

2001

The present study addresses problems and solutions related to new functional bio-active food product creation. Commercial rolled oats and fat-free milk were used as raw materials. Limited enzymatic hydrolysis of oat starch was carried out by α-amylase. The lactic acid bacteria strains Lactobacillus acidophilus, Bifidobacterium sp., and commercial starter cultures ABT-1 were cultivated in enzymatically hydrolysed oat mash. Lactobacillus acidophilus was a more active producer of lactic acid, while Bifidobacterium sp. improved the taste properties. A fat-free milk additive was applied to stabilise the texture of the oat mash, and increase the protein content of the final product. All procedure…