Search results for "Hydrolysis"
showing 10 items of 632 documents
Effect of L-Histidine on the Survival of a T-Strain of Mycoplasma
1975
The addition of L-histidine to the growth medium prolongs the stationary phase and the survival of a T-strain of mycoplasma. Results of an experiment performed with 14 C-labeled urea demonstrate that the action of L-histidine is based on the retardation of the rise of pH.
Enzyme-Controlled Nanodevice for Acetylcholine-Triggered Cargo Delivery Based on Janus Au–Mesoporous Silica Nanoparticles
2017
[EN] This work reports a new gated nanodevice for acetylcholine-triggered cargo delivery. We prepared and characterized Janus Au-mesoporous silica nanoparticles functionalized with acetylcholinesterase on the Au face and with supramolecular b-cyclodextrin: benzimidazole inclusion complexes as caps on the mesoporous silica face. The nanodevice is able to selectively deliver the cargo in the presence of acetylcholine via enzyme-mediated acetylcholine hydrolysis, locally lowering the pH and opening the supramolecular gate. Given the key role played by ACh and its relation with Parkinson's disease and other nervous system diseases, we believe that these findings could help design new therapeuti…
Design of enzyme-mediated controlled release systems based on silica mesoporous supports capped with ester-glycol groups
2012
[EN] An ethylene glycol-capped hybrid material for the controlled release of molecules in the presence of esterase enzyme has been prepared. The final organic-inorganic hybrid solid S1 was synthesized by a two-step procedure. In the first step, the pores of an inorganic MCM-41 support (in the form of nanoparticles) were loaded with [Ru(bipy) 3]Cl 2 complex, and then, in the second step, the pore outlets were functionalized with ester glycol moieties that acted as molecular caps. In the absence of an enzyme, release of the complex from aqueous suspensions of S1 at pH 8.0 is inhibited due to the steric hindrance imposed by the bulky ester glycol moieties. Upon addition of esterase enzyme, del…
Autolysis of Yeasts
2011
Autolysis of yeast cells occurs after they have completed their life cycle and entered the death phase. It is characterized by a loss of cell membrane permeability, alteration of cell wall porosity, hydrolysis of cellular macromolecules by endogenous enzymes, and subsequent leakage of the breakdown products into the extracellular environment. Although a naturally occurring event, autolysis can be induced by exposing yeasts to elevated temperatures (40–60 °C), organic solvents, or detergents. Yeast autolysis occurs in many foods and beverages, where it may affect their sensory quality and commercial acceptability.
Comparison of simultaneous saccharification and fermentation and separate hydrolysis and fermentation processes for butanol production from rice straw
2020
Abstract Rice straw (RS) is one of the lignocellulosic wastes with the highest global production. The main objective of this study was to maximise the butanol production by Clostridium beijerinckii DSM 6422 from RS pretreated by microwave-assisted hydrothermolysis. Two different fermentation strategies were compared: separate hydrolysis and fermentation (SHF, two-step process) and simultaneous saccharification and fermentation (SSF, one-step process). In parallel, the variables that significantly affected the butanol production were screened by using fractional factorial designs. Butanol concentration and productivity at 48 h were, respectively, 8% and 173% higher in SSF than in SHF. A one-…
Speciation of Al3+ in fairly concentrated solutions (20 to 200 mmol L-1) at I = 1 mol L-1 (NaNO3), in the acidic pH range, at different temperatures.
2011
AbstractThe hydrolysis of Al3+ was studied in aqueous 1 mol L−1 NaNO3 solution at different concentrations (20–200 mmol L−1) and temperatures (283.15–343.15 K) by potentiometry (ISE-H+, glass electrode). Many different speciation models were considered in the calculations and it was found that the best model is represented by the following species: Al(OH)2+, Al(OH)45+, Al13(OH)327+. Hydrolysis constants and enthalpy changes at different temperatures are reported.
A comparative study of the physicochemical properties of iron isomaltoside 1000 (Monofer®), a new intravenous iron preparation and its clinical impli…
2011
Abstract The treatment of iron deficiency anemia with polynuclear iron formulations is an established therapy in patients with chronic kidney disease but also in other disease areas like gastroenterology, cardiology, oncology, pre/post operatively and obstetrics’ and gynecology. Parenteral iron formulations represent colloidal systems in the lower nanometer size range which have traditionally been shown to consist of an iron core surrounded by a carbohydrate shell. In this publication, we for the first time describe the novel matrix structure of iron isomaltoside 1000 which differs from the traditional picture of an iron core surrounded by a carbohydrate. Despite some structural similaritie…
Chemical and catalytical properties of thermal polymers of amino acids (proteinoids)
1974
The significance of thermal polyamino acids (proteinoids) as abiotic predecessors of proteins is reviewed on the basis of new experimental results. Most proteinoids yield only 50% to 80% amino acid upon acid hydrolysis. They contain 40% to 60% less peptide links than typical proteins, whereas their average nitrogen content is like that of proteins. The arrangement of amino acid residues is nonrandom. The degree of nonrandomness is difficult to determine because unusual crosslinks disturb most of the sequencing methods typically applied in protein chemistry. The products obtained in a polymerization experiment are heterogeneous. They can be separated into a limited number of related fraction…
Mixed monolayers of natural and polymeric phospholipids: structural characterization by physical and enzymatic methods
1990
This study has focused on physical characterization and enzymatic hydrolysis of mixed monolayers of a natural phospholipid substrate and a polymerizable phospholipid analogue. Such a mixed system presents the possibility to stabilize model biomembranes, vary the molecular environment within the layer through polymerization and simultaneously examine these influences on monolayer structure. Phospholipase A2 was used here as a sensitive probe of the molecular environment within these mixed, polymerizable monolayers to complement information obtained from isotherm and isobar data. The results clearly show a strong influence of molecular environment on phospholipase A2 activity, even if differe…
Junceosides A-C, new triterpene saponins from Arenaria juncea.
2002
Three novel triterpenoid saponins, junceosides A (1), B (2), and C (3), together with two known saponins have been isolated from the roots of Arenaria juncea. Their structures were elucidated using a combination of homo- and heteronuclear 2D NMR techniques (COSY, TOCSY, NOESY, HSQC, and HMBC) and by FABMS. The new compounds were characterized as 3-O-alpha-L-arabinopyranosyl-(1-->2)-[beta-D-galactopyranosyl-(1-->3)]-beta-D-glucuronopyranosylgypsogenin-28-O-beta-D-glucopyranosyl(1-->3)-[beta-D-xylopyranosyl-(1-->4)]-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-fucopyranoside (1), 3-O-alpha-L-arabinopyranosyl-(1-->2)-[beta-D-galactopyranosyl-(1-->3)]-beta-D-glucuronopyranosylgypsogenin-28-O-beta-D-x…