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At least 811 records · Page 45Linked to original sources
PubMed1996

Separation of biosynthetic oligosaccharide branch isomers using high-performance liquid chromatography on a porous two-dimensional graphite stationary phase.

Oligomannosidic branch isomers (structures differing only in the branch location of a single residue) which are biosynthetic intermediates in yeast and higher eukaryotics have been separated using high-performance liquid chromatography (HPLC) on porous graphatized carbon (PGC) columns, a stationary phase of two-dimensional crystalline carbon. A mixture of two Man6GlcNAc isomers from IgM, which was determined from 1H NMR analysis, was completely separated by PGC-HPLC. Mixtures of larger yeast oligomannosidic branch isomers were also chromatographically resolved using PGC-HPLC. Man10GlcNAc and Man11GlcNAc species from invertase expressed in Pichia pastoris showed three and five peak fractions, respectively, by PGC-HPLC in agreement with the number of isomeric forms from one- and two-dimensional 1H NMR analyses of the individual sized fractions (Trimble, R. B., Atkinson, P. H., Tschopp, J. R., Townsend, R. R., and Maley, F. (1991) J. Biol. Chem. 266, 22807-22817). Selected peak fractions were further analyzed to confirm assignments using matrix- assisted laser-desorption mass spectrometry after digestion with an alpha(1 --> 2)-specific mannosidase (Aspergillus saitoi). PGC-HPLC should prove invaluable for the preparation of singular oligosaccharides to define exoglycosidase and glycosyl transferase branch specificity and for preparing standards to develop more sensitive methods for structural elucidation of oligosaccharides.

Aspergillus↗
PubMed2004

Determination of chlorite in drinking water by differential pulse voltammetry on graphite.

The chlorite ion is an unavoidable by-product of the disinfection of drinking water by means of chlorine dioxide. The maximum concentration values of chlorite accepted in many countries' regulations range from 0.2 to 1.0 mg L(-1). A simple, inexpensive and quickly set up voltammetric procedure for the on-site determination of chlorite in drinking water networks is described. This procedure is suitable for the whole range of applications in drinking water plants. A useful cell for on-field analysis has been developed. Surface morphology and behaviour of carbon-based working electrodes have been investigated by voltammetry and atomic force microscopy (AFM). Actual samples of different types of water networks have been analysed for chlorite concentration.

Chlorides↗
PubMed1985

Matrix modifiers in graphite furnace atomic absorption analysis of trace lithium in biological fluids.

The use of KH2PO4/NH4NO3 as matrix modifier eliminates severe interference effects on the atomic absorption analysis of lithium in biological fluids. This enables determination of trace lithium in microliter size samples with absolute sensitivity (0.0044 absorbance) of 2 pg. There is no requirement for standard additions experiments to correct for interferences in specific matrices such as serum and saliva. The biological half-life of trace lithium was 16.9 +/- 2.8 h. Saliva lithium is a good estimate of serum level; the two are highly correlated (r = 0.97) and saliva level is about three times serum.

Adult↗
PubMed1985

Serum and dialysate aluminium concentration of dialysed patients with chronic renal failure determined by atomic absorption spectrometry with a graphite furnace.

We investigated the aluminium content in water, in solutions for haemodialysis and in serum of patients, under regular haemodialysis using flameless atomic absorption spectroscopy with l'Vov platform. The aluminium content found for tap water was 6-36 micrograms/l. After deionization the aluminium content was negligible. The dialysis bath, prepared with deionized water from a concentrated solution with 30 micrograms/l of aluminium, also showed a negligible amount of aluminium. The results obtained showed that patients who take aluminium orally have predialytic aluminium serum levels between 14 and 68 micrograms/l and between 10 and 66 after dialysis. For patients who do not take aluminium orally, the corresponding values were 12-27 and 12-24. No correlation was found between age, sex, years of dialysis and aluminium serum levels.

Adult↗
PubMed1992

High-performance liquid chromatography of oligosaccharide alditols and glycopeptides on a graphitized carbon column.

The chromatographic behaviour of oligosaccharide alditols and glycopeptides containing neutral and acetamido sugars and sialic acid has been investigated on a HyperCarb porous graphitised carbon column. The alditols were substantially retained and could be eluted in 0-25% acetonitrile-0.05% trifluoroacetic acid in 0.05% aqueous trifluoroacetic acid between 3-30 min for mono- to hexasaccharides. Elution patterns were based on both size, charge and linkage such that isomeric compounds could be separated from each other.

Amino Acid Sequence↗
PubMed2005

Electrochemical oxidation of 2-thiouracil at pyrolytic graphite electrode.

2-Thiouracil has been studied in phosphate buffers of pH 1.95-11.08 using linear and cyclic sweep voltammetry, coulometry, controlled potential electrolysis and spectral studies. One well-defined oxidation peak I(a) in the pH range 1.95-11.08 was noticed. The number of electrons involved in peak I(a) was found to be four in a thin layer cell whereas under exhaustive electrolysis condition oxidation was found to involve six electrons. A reduction peak II(c) (2e, 2H(+)) is noticed in the reverse sweep. Spectral studies during oxidation were carried out at different pH. Kinetic studies indicated that the decay of the UV-absorbing intermediate is a first order reaction. The products of the electrooxidation have been characterized and a tentative EC mechanism has been suggested for the oxidation of 2-thiouracil.

Electrochemistry↗