Search results for " High pressure liquid"
showing 10 items of 705 documents
Identification and structural characterization of O-beta-ribosyl-(1"----2')-adenosine-5"-phosphate in yeast methionine initiator tRNA.
1990
We report in this paper on the complete structure determination of the modified nucleotide A*, now called Ar(p), that was previously identified in yeast methionine initiator tRNA as an isomeric form of O-ribosyl-adenosine bearing an additional phosphoryl-monoester group on its ribose2 moiety. By using the chemical procedure of periodate oxidation and subsequent beta-elimination with cyclohexylamine on mono- and dinucleotides containing Ar(p), we characterized the location of the phosphate group on the C-5" of the ribose2 moiety, and the linkage between the two riboses as a (1"----2')-glycosidic bond. Since the structural difference between phosphatase treated Ar(p) and authentic O-alpha-rib…
Amino acid contents of infant foods.
2006
The protein quality of three milk-cereal-based infant foods (paps) was evaluated by determining their amino acid contents and calculating the amino acid score. Proteins were subjected to acid hydrolysis, prior to which cysteine and methionine were oxidized with performic acid. Amino acids were determined by reverse-phase high-performance liquid chromatography with fluorescence detection with a prior derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. Tryptophan was determined by reverse-phase high-performance liquid chromatography with ultraviolet detection after basic hydrolysis. Glutamic acid, proline and leucine were the most abundant amino acids, whereas tryptophan and …
A fast method for determining low-molecular-mass aliphatic carboxylic acids by high-performance liquid chromatography–atmospheric pressure chemical i…
2006
A fast quantitative high-performance liquid chromatographic separation method with atmospheric pressure chemical ionization mass spectrometric detection (HPLC-APCI-MS) was developed for the determination of low-molecular-mass aliphatic mono- and dicarboxylic acids typically present in different industrial process waters. A mixture of glycolic, lactic, a-glucoisosaccharinic, oxalic, maleic, fumaric, succinic, malic, glutaric, methylsuccinic, and adipic acids was separated using an RP chromatographic system. Adipic acid was used as an internal standard to calculate correlation coefficients for the acids studied. The chromatographic analysis of these acids was primarily carried out by means of…
Quantitative determination of the main aliphatic carboxylic acids in wood kraft black liquors by high-performance liquid chromatography-mass spectrom…
2006
The versatile characterization of organic material and especially of the significant aliphatic hydroxy acids in black liquor is of great importance, for example, in monitoring the progress of the kraft pulping process. This paper describes a simple high-performance liquid chromatographic separation method with atmospheric-pressure chemical ionization mass spectrometry (HPLC-APCI-MS) which was developed for the rapid quantitative analysis of these acids, mainly formed as the alkaline degradation products of feedstock carbohydrates. The fraction of carbohydrate degradation products is mainly composed of hydroxy monocarboxylic and volatile acids (formic and acetic acids) along with lesser amou…
The determination of the DNA base composition in 19 species of adriatic sponges with high-pressure liquid cation-exchange chromatography.
1976
Abstract The (adenine + thymine)/(guanine + cytosine) base ratios of 19 species of adriatic sponges have been determined by high-pressure liquid cation-exchange chromatography. The base ratios vary from 1.49 (Mycale massa) to 0.63 (Hippospongia communis) according to an (A+T) content of 59.7 and 38.6 mol%, respectively. The DNAs of sponges of the order Keratosa showed marked differences in their (A +T) contents (39.5 to 58.8 mol%) whereas those of Tetractinellida and Halichondrina were nearly identical (39.3 to 40.8 and 49.5 to 49.8 mol%, respectively). The 5-methylcytosine (5MC) content was determined in 8 sponge DNAs by a semiquantitative method. The values differed from 0.8 to 2.2 mol% o…
Application of molecularly imprinted polymers in supercritical fluid chromatography
2000
Molecularly imprinted polymers (MIPs), for the templates free base racemic propranolol and the L-enantiomer of phenylalanine anilide (L-PA), were investigated as stationary phases in supercritical fluid chromatography (SFC). Large retention differences were observed on the propranolol MIP for both the template molecule and the structural analogue metoprolol compared to that observed on the corresponding blank polymer. Mobile phase composition and solute concentration were found to affect this retention behaviour. The phenylalanine anilide MIP (L-PA MIP) was found to be enantioselective in SFC with stronger retention observed for the template enantiomer. Throughout the study, characteristic …
Retention behaviour of paracelsin peptides on reversed-phase silicas with varying n-alkyl chain length and ligand density.
1989
As part of further investigations on the characterization of the ligand-induced conformational stabilization of peptides, two series of n-alkyldimethylsilyl bonded silicas have been prepared. In series A the n-alkyl chain length, n, of the bonded phase was varied between 1 and 20 carbon atoms at a constant ligand density. In series B the ligand density, alpha exp, was gradually changed from 0 to 4.1 mumol/m2 on a C1, C4, C6, C8 and C18 bonded phase. The retention behaviour of four peptides of the paracelsin family were examined under isocratic conditions, using a ternary mobile phase of water-methanol-acetonitrile (22:39:39, v/v/v). Plots of k' versus n showed pronounced maxima between n = …
Imprinted chiral stationary phases in high-performance liquid chromatography
2001
Polymers imprinted with chiral templates offer a new generation of tailor-made chiral stationary phases (CSPs) with predictable selectivities. This review summarizes the present state of the art of molecular imprinting to generate tailor-made CSPs and provides an overview of the main factors involved in the manufacturing process that are crucial to the chromatographic performance of the phases.
Enzyme class identification in cleaning products by hydrolysis followed by derivatization with o-phthaldialdehyde, HPLC and linear discriminant analy…
2008
The enzymes present in raw materials of the cleaning industry (enzyme industrial concentrates) and in household cleaners were isolated by precipitation with acetone and hydrolyzed with HCl. The resulting amino acids were derivatized with o-phthaldialdehyde, and the derivatives were separated by HPLC. The peaks of 14 amino acids were observed using a C18 column and a multi-segmented gradient of acetonitrile-water in the presence of a 5 mM citric/citrate buffer of pH 6.5. Using either normalized peak areas (divided by the sum of the peak areas of the chromatogram) or ratios of pairs of peak areas as predictor variables, linear discriminant analysis models, capable of predicting the enzyme cla…
Analysis of amino acids using serially coupled columns.
2017
Single conventional columns in reversed-phase LC are insufficient for analysing the isoindoles of primary amino acids, due to their limited functionality. An interesting possibility for increasing the separation power is the combination of several columns of different nature, where the length is modified by coupling small segments. This approach may require a considerable investment to have multiple lengths for each stationary phase. However, the combination of only two columns of fixed length can be enough to resolve satisfactorily relatively complex mixtures, provided that an optimised gradient program is applied. In this work, a mixture of 19 primary amino acid isoindoles found in protei…