Search results for "acid hydrolysis"
showing 10 items of 38 documents
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…
Stability of levan produced by Zymomonas mobilis
2005
Abstract The stability of levan produced by Zymomonas mobilis 113 “S” was investigated during storage of culture liquid at different pH and temperatures. Levan was not degraded if stored in a culture liquid for 120 h at 30 or 25 °C, but at 55 or 60 °C the degree of degradation was inversely proportional to pH. Cell biomass and levan sediment components did not cause the degradation of levan. The influence of organic acids (lactic-, acetic-, and gluconic) and HCl as levan hydrolyzing agents at pH 3.7, temperature 30 °C or 55 °C was investigated in a model solution. The hydrolytic effect was similar in the case of organic acids—ensuring more fructose formation, while HCl ensured higher amount…
Synthesis of large-pore ordered mesoporous silicas containing aminopropyl groups
2005
Ordered mesoporous silicas with large-pore diameters incorporating aminopropyl groups in variable quantity have been synthesized via the co-condensation of tetraethyl orthosilicate (TEOS) and 3-tert-butyloxycarbonylaminopropyltriethoxysilane templated with nonionic surfactant P123 under acidic conditions. The deprotection of amino groups was then quantitatively achieved either by thermal treatment or acid hydrolysis followed by Et3N treatment, both routes leading to exactly the same materials. We showed that the free amino centers are fully accessible, by using the condensation of the amine function with benzaldehyde.
The identification of irradiated crustaceans and evaluation of the dose by thermoluminescence: Intercomparison between two methods for extracting min…
2010
Abstract The thermoluminescence (TL) is one of the physical methods recommended by the European Committee for Standardization, for the identification of irradiated food from which silicate minerals can be extracted. The efficacy of the method strongly depends on the quantity and purity of the extracted minerals, and therefore on the extraction procedure. In this work we applied the TL for the identification of crustacean Nephrops norvegicus irradiated at 0.5−1.5−3.0 kGy, comparing two different procedures for extracting minerals: by means of a density gradient or with acid hydrolysis. The identification of the irradiation treatment was always achieved with both procedures, without any false…
Amino acid profile of milk-based infant formulas
2000
The protein content and amino acid profile of three milk-based infant formulas, two of which were powdered (adapted and follow-on) and the third liquid, were determined to check their compliance with the EU directive and to evaluate whether or not they fulfil an infant's nutritional needs. To obtain the amino acid profile proteins were subjected to acid hydrolysis, prior to which the sulfur-containing amino acids were oxidized with performic acid. The amino acids were derivatized with phenylisothiocyanate (PITC) and then determined by ion-pair reverse phase high performance liquid chromatography (HPLC) In the case of tryptophan a basic hydrolysis was applied and there was no need of derivat…
Über die bestimmung des zahlenmittels des molekulargewichts von polyoxymethylenen. 36. Mitt. Über polyoxymethylene
1968
Die Bestimmung des Zahlenmittels des Molekulargewichts (Mn) von Polyoxymethylenen durch Osmose, durch Kryoskopie, durch chemische und infrarotspektroskopische Endgruppenbestimmung und durch andere Methoden wird diskutiert. Osmotische Messungen in Phenol bei 90°C gelangen mit Cellophanmembranen besser als mit Glasmembranen. Kryoskopische Messungen nach RAST in Campher ergaben nur in Gegenwart eines Antioxydans zuverlassige Ergebnisse. Zur Endgruppenanalyse wurde vor allem die infrarotspektroskopische Bestimmung von Acetatgruppen weiterentwickelt; zur Auswertung wurde die Intensitat der Carbonylbande bei 5,70 μ in Beziehung gesetzt zu der CH2-Bande bei 6,8 μ und eine Eichung mit Hilfe des Chr…
Nucleophilic reactions in the indole series: displacement of bromine under phase transfer catalysis
2008
A novel synthetic approach for the synthesis of 3-substituted indoles by nucleophilic substitution of 3-bromo derivatives under phase transfer catalysis (PTC) was reported.
Polycondensed nitrogen heterocycles. Part13. Pyrrolo[3,2-b]indole by intramolecular nucleophilic substitution reaction in the pyrrole series
1984
An intramolecular nucleophilic substitution in the pyrrole series has been generalized. The behaviour of nitro, chlorine, bromine and iodine as leaving groups towards the nucleophilic amino group was observed. An acid catalyzed mechanism has been proposed.
Structure of a polysaccharide from the lipopolysaccharide of Vibrio vulnificus CECT4602 containing 2-acetamido-2,3,6-trideoxy-3-[(S)- and (R)-3-hydro…
2008
A polysaccharide was isolated by GPC after mild acid treatment of the lipopolysaccharide of Vibrio vulnificus CECT4602 and found to contain L-Rha, D-GlcpNAc and 2-acetamido-2,3,6-trideoxy-3-(3-hydroxybutanoylamino)-L-mannose (L-RhaNAc3NHb). GLC analysis of the trifluoroacetylated (S)-2-octyl esters derived by full acid hydrolysis of the polysaccharide showed that approximately 80% of the 3-hydroxybutanoic acid has the S configuration and approximately 20% the R configuration. The following structure of the polysaccharide was established by (1)H and (13)C NMR spectroscopies, including 2D ROESY and (1)H/(13)C HMBC experiments: [carbohydrate sequence see in text].
A hypotensive procyanidin-glycoside from Rhamnus lycioides ssp. lycioides.
1990
A lyophilized hot water extract of the aerial parts of Rhamnus lycioides L. (Rhamnaceae) produced a lowering of systemic arterial blood pressure in normotensive anaesthetized Wistar rats. An activity-guided fractionation of the methanolic extract led to the isolation of a tetrameric procyanidin-glycoside which produced a clear dose-dependent hypotensive response (1.5-6 mg/kg i.v.). This principle was characterized using acid hydrolysis, thiolytic degradation and spectroscopic methods. It consisted of four flavanol units with a 2,3-cis configuration and with a O-beta-d-glucosylpyranoside function on the epicatechin terminal unit. The interflavan linkage was (4-8).