Search results for "Cyst"
showing 10 items of 1960 documents
Use of pH gradients in continuous-flow systems and multivariate regression techniques applied to the determination of methionine and cysteine in phar…
1997
Abstract The simultaneous spectrophotometric determination of methionine and cysteine in presence of cystine and other compounds in pharmaceuticals, using a multivariate calibration method, was studied. The method is based on the reaction between the analytes and the o- phthalaldehyde -N- acetyl - l - cysteine (OPA-NAC) reagent performed in a continuous-flow system (FI). The FI system allows the generation of a local pH gradient in order to produce spectral and/or kinetic changes in the UV-Vis spectra of the amino acid-OPA-NAC derivatives. This information is used to improve the prediction ability of the Partial Least-Squares (PLS) models. The performance of two FI assemblies, the selection…
Cysteamine and its homoleptic complexes with group 12 metal ions. Differences in the coordination chemistry of ZnII, CdII, and HgII with a small N,S-…
2005
2-Ammoniumethanethiolate, (-)SCH(2)CH(2)NH(3)(+), the first structurally characterized zwitterionic ammoniumthiolate, is the stable form of cysteamine (HL) in the solid state and in aqueous solution. Reactions of ZnCl(2), Cd(Oac)(2), and HgCl(2) with cysteamine and NaOH in a 1:2:2 ratio, respectively, lead to the homoleptic complexes ML(2). Their single-crystal X-ray structures demonstrate basic differences in the coordination chemistry of Zn(II), Cd(II), and Hg(II). While chelating N,S-coordination modes are found for all metal ions, Zn(II) forms a mononuclear complex with a distorted tetrahedral Zn(N(2)S(2)) coordination mode, whereas Hg(II) displays a dimer with Hg(N(2)S(2)) coordinated …
Mathematic predictive models for calculating copper, iron and zinc dialysability in infant formulas
2001
Differences in the dialysability of a mineral element from infant formulas of the same type were detected in a previous study. As these may be due to the effects that different levels of the components of the formulas could have on dialysability, we attempted to establish mathematical models to predict the dialysability of Cu, Fe and Zn from infant formulas according to their ascorbic, citric, or selected amino acid contents. A simple linear regression was applied between the ascorbic acid, citric acid and amino acid contents and the Cu, Fe and Zn dialysability of 18 powdered infant formulas of different types. Significant correlations (P<0.05) were obtained between the dialysability of Fe …
Thioredoxin-related protein of 14 kDa may directly reduce protein cysteinylation motifs
2018
Disulfide stress has been associated with inflammation and characterized by an increase in cystine levels and protein cysteinylation. Furthermore, it was recently discovered that thioredoxin-related protein of 14 kDa (TRP14, encoded by TXNDC17) exhibits efficient cystine reductase activity. The aim of our research was to elucidate if TRP14 is also able to reduce cysteinylated proteins in mammalian cells. Thus, protein cysteinylation was assessed in control and TRP14 knockdown cells in vitro through their pre-treatment with 25 µg/ml cycloheximide for 30 min and incubation with 250 µM biotinylated cysteine for 1 h. Moreover, such TRP14 knockdown cell lysates were tested as cysteinylated subst…
Spectrophotometric Determination of Cystine with O-Phthalaldehyde in the Absence of Thiol
1988
Abstract A spectrophotometric method for the determination of cystine with o-phthalaldehyde (OPA) in the absence of thiol is described. When cystine is heated at 60[ddot]C for 30 min in a low excess of OPA (pH 9.5), a very stable derivative with 1:2 stoichiometry (cystine:OPA) and an absorption maximum at 335 nm (E = 4600) is formed. At pH < 1 the derivative is protonated (protonation constants: log K1 = 5.88 and log K2 = 3.70 at I = 0.1 and 20[ddot]C) and another absorption band at 440 nm (E = 3800) appears, which allows the determination of cystine in the presence of other amino acids.
Determination of the protein and free amino acid content in a sample using o-phthalaldehyde and N-acetyl-L-cysteine
1990
A spectrophotometric method is proposed for determining the protein content in a sample after total acid hydrolysis. In the procedure, free amino acids are caused to react with o-phthalaldehyde and N-acetyl-L-cysteine at pH 9.5, using isoleucine as the reference compound. Correction factors are used to take into account the differences between the molar absorptivities of the amino acid isoindoles and the recoveries of the amino acids after the hydrolysis treatment. The limit of detection was in the range 40-50 micrograms of protein, and the recoveries were usually 101 +/- 3% with a coefficient of variation lower than 4%. The free amino acid content in a partially hydrolysed protein was also…
Detection and localisation of disulphide bonds in a synthetic peptide reproducing the sequence 1-30 ofPar j1.0101 by electrospray ionisation mass spe…
2001
The structural characterisation of a synthetic peptide reproducingthe sequence 1–30 of Par j 1.0101, a major allergenic protein present in the pollen of Parietaria judaica, by combined use of chemical and enzymatic cleavage, reversed-phase high-performance liquid chromatography (RP-HPLC) and electrospray ionisation mass spectrometry (ESI-MS), is described. Direct ESI-MS of the synthetic peptide after reaction with methyl iodide showed that the product is a mixture of two peptides: one form in which two out of the four cysteine residues present in the sequence are oxidised and a minor amount of another form in which all the cysteines are fully reduced. It was ascertained, usingthe combined p…
Zum Nachweis enzymatischer Mechanismen in menschlicher Epidermis am Modell der subepidermalen Blase
1959
1. In Epidermis, die durch subepidermale Blasenbildung bei Alterspemphigus komplett von der Cutis abgehoben war, konnten aus der glykolytischen Kette und dem Citronensaurecyclus an Fermenten und Substraten nachgewiesen werden: Aldolase, Brenztraubensaure, Milchsauredehydrogenase, Milchsaure, Glutaminsaure-Brenztraubensaure-Transaminase, Apfelsauredehydrogenase, α-Ketoglutarsaure, Glutaminsaure-Oxalessigsaure-Transaminase und Glutaminsaure. 2. Es konnte der Nachweis erbracht werden, das diese Enzyme und Metaboliten nicht nur in menschlicher Epidermis angetroffen, sondern auch von ihren Zellagen selbst produziert werden. 3. Die vergleichenden quantitativen Untersuchungen sind ein Beweis, das …
Environmentally relevant precursors of carbonyl sulfide in aquatic systems
1997
Seawater solutions of environmentally relevant organosulfur compounds, commercial humic acid (HA), and natural dissolved organic matter (DOM) were incubated with and without UV light in order to determine the carbonyl sulfide (COS) producing capabilities of these compounds. COS dark- and photo-production rate constants were determined for dilute solutions of the organosulfur compounds (μmol l−1) and HA/DOM (mg l−1). Dissolved COS was determined using a purge and cryogenic trap method followed by GC/FPD detection. COS was produced in considerable amounts both non-photochemically and photochemically from the reduced form of free acid of glutathione (GSH) and photochemically from cysteine (CYS…
Spectrophotometric determination of cystine by formation of an o-phthalaldehyde/N-acetyl-l-cysteine derivative
1989
Abstract Cystine reacts with o -phthalaldehyde (OPA) in the absence and presence of a thiol compound to yield different compounds. The use of N -acetyl- l -cysteine as thiol leads to the formation of two derivatives, likely simple and double isoindoles, where the disulfide bond remains unbroken. In contrast, mercaptoethanol gives rise to the reduction of the amino acid to form a cysteine derivative. Obtaining cystine isoindoles makes it possible to spectrophotometrically determine the amino acid after Chromatographic separation and is further evidence of the large stabilization effect produced by N -acetyl- l -cysteine in the formation of OPA-thiol derivatives.