Low-pressure Ion-exchange Chromatography Research Articles

Tin compounds in food - their distribution and determination

The aim of this work was optimization of the methods of trace- and ultratrace analysis, such as ICP-OES, ETA-AAS for charting the resources of individual forms of tin in foodstuffs. Increase of the sensitivity of the method of ICP-OES was achieved using the techniques of generation of hydrides, which was also optimized. Based on the information available on the occurrence of the different forms of tin, it appears that many of these organometallic compounds are contained in marine animals; attention has mainly focused on organisms such as marine fish, crustaceans, molluscs and algae. Tin compounds of predominantly inorganic origin can be found in foods and beverages which are packed in cans with a protective tin coating, too. The above mentioned methods have been applied to the analysis of selected beverages with low content of tin such as Coca Cola, Sprite, Fanta, Gambrinus 10°, PowerKing, and milk in the cans. Furthermore samples of animal origin as Sardines in oil, and Hunter's salami were examined, too. Prior to the determination of tin, samples need to be appropriately modified or analysed. Decomposition of the samples was done in the microwave system. Low pressure ion exchange chromatography with on-line detection of ICP-OES was used for separation of inorganic tin compounds. Separation of organically bound tin compounds was performed by HPLC on a column of ACE C-18, 3 µm, 15 cm × 1.0 mm with off-line detection by ETA-AAS. All of the above forms of tin compounds can be separated with this column. Due to the improvement in the detection of organically bounded tin, HPLC with identical ACE C-18 column coupled online for example with ICP-MS or spectrofluorimetry could be recommended.

Isolation of Peptides from Calf Brain Tissue and Evaluation of their Tissue-Specific and Stimulatory Activity

A method for separating a mixture of calf brain peptides by extraction with aqueous HOAc followed by fractionation of the extract by cross-flow (tangential) microfiltration and solid-phase extraction was developed. The isolated peptide mixture contained constituents with molecular masses within 0.1 – 3 kDa. Low-pressure ion-exchange chromatography of this mixture over Dowex 50WX8 sulfonated cation exchanger isolated a pure peptide consisting of the five amino acids Arg, Lys, Gly, Ser, and Leu. The biological activity of the obtained pentapeptide was estimated on organotypic brain slice culture explants of Wistar rats. It was established that the peptide possessed high tissue-specific and stimulatory activity for brain explants that was greater than those of the commercial preparations Cortexin and Cerebrolysin.

Выделение пептидов из ткани головного мозга телят и оценка их тканеспецифической и стимулирующей активности

Разработан метод выделения смеси пептидов из головного мозга телят экстрагированием водным раствором уксусной кислоты с последующим фракционированием экстракта тангенциальной микрофильтрацией и твёрдофазной экстракцией. Выделенная смесь пептидов содержит компоненты с молекулярными массами от 0,1 до 3 кДа. Из этой смеси методом ионообменной хроматографии низкого давления на сульфокатионите Dowex 50WX8 выделен индивидуальный пептид, состоящий из 5 аминокислот: Arg, Lys, Gly, Ser, Leu. Биологическую активность полученного пентапептида оценивали в органотипической культуре эксплантатов мозга крыс линии «Вистар». Показано, что пептид проявляет выраженную тканеспецифическую и стимулирующую активность по отношению к эксплантатам мозга, превышающую активность коммерческих препаратов кортексин и церебролизин.

Simultaneous determination of chloride, bromide and iodide in foodstuffs by low pressure ion-exchange chromatography with visible light detection

An ion-exchange chromatography method with visible light detection was developed for the simultaneous determination of chloride, bromide, and iodide in foodstuffs. They were separated by means of low pressure ion-exchange chromatography using 4.0mM sodium carbonate solution as the eluent and a low pressure ion-exchange chromatography column as the separation column. The detection limits of chloride, bromide and iodide were 0.011 mg/l, 0.002 mg/l, and 0.023 mg/l, respectively. The relative standard deviations (RSDs) of the peak area were smaller than 2.9%. The recoveries were between 98.61% and 105.65%. Unlike the traditional methods, this validated method is inexpensive and stable.

Characterization of Exoskeletal Proteins from the American Lobster, Homarus americanus

Proteins from the calcified exoskeleton of the lobster, Homarus americanus, were extracted and separated by two-dimensional gel-electrophoresis. Electroblotting the proteins onto polyvinylidene difluoride (PVDF) membranes followed by sequence determination gave 16 N-terminal amino-acid sequences and revealed that further eight proteins were N-terminally blocked.The relative molecular mass, Mr, was obtained for most of the electrophoretically separated proteins by means of matrix-assisted laser desorption mass spectrometry (MALDIMS) after electroelution from Coomassie-stained two-dimensional polyacrylamide gels.Eleven proteins were purified from extracts of the exoskeleton by low pressure ion exchange chromatography and reversed-phase high performance chromatography, and their sequences were determined by combined use of Edman degradation and mass spectrometry. Good agreement was obtained between the Mr-values measured by mass spectrometry and those calculated from the sequences.Five of the sequenced proteins contain two copies of a previously observed 18-residue sequence motif, while a couple of the remaining sequences show similarity to sequences of exoskeletal proteins from shrimps and spiders. Only limited similarity to insect cuticular proteins was observed.

The chemistry of uranium in evaporation pond sediment in the San Joaquin valley, California, USA, using X-ray fluorescence and XANES techniques

Evaporation ponds in the San Joaquin Valley (SJV), CA, used for the disposal of irrigation drainage waters, contain elevated levels of uranium. The ponds are filled periodically and support algae which upon evaporation become incorporated in the sediments as layers of decaying organic matter. This rich source of organic matter promotes reducing conditions in the sediments. Our research was conducted to characterize oxidation/ reduction reactions that affect soluble and sediment U(IV)/U(VI) concentrations in the SJV ponds. Studies were done to (1) determine soluble U(VI)/U(IV) in waters in contact with a pond sediment subjected to changes in redox status, (2) observe U solid oxidation state as a reducing pond sediment underwent (in vitro) oxidation, and (3) determine U solid oxidation state with respect to depth in pond surface sediment layers. Low pressure ion-exchange chromatography with an eluent of 0.125 M H 2C 2O 4/0.25 M HNO 3 was used for the separation of U (IV) and U(VI) oxidation states in the drainage waters. Soluble U(VI) and U(IV) coexisted in sediment suspensions exposed to changes in redox potential (Eh) (-260 mV to +330 mV), and U(VI) was highly soluble in the oxidized, surface pond sediments. X-ray near edge absorption spectroscopy (XANES) showed that the U solid phases were 25% U(IV) and 75% U(VI) and probably a mixed solid [U 3O 8(s)] in highly reducing pond sediments. Sediment U (IV) increased slightly with depth in the surface pond sediment layers suggesting a gradual reduction of U (VI) to U (IV) with time. Under oxidized conditions, this mixed oxidation-state solid was highly soluble.

Performance comparison of low-pressure ion-exchange chromatography media for protein separation

The physical and functional performance of 70 different anion- and cation-exchange media based on cellulose, agarose, dextran and polymeric/composite materials has been evaluated. Physical tests such as swelling, flow performance and column packing densities and functional tests including small-ion capacity, protein capacity and chromatographic performance were carried out on each grade. The data, descriptive rather than prescriptive, demonstrates significant performance differences from medium to medium and suggest that a rigorous media screening exercise be carried out prior to developing an ion-exchange separation process, in order to optimise the efficiency of the process.

A six-armed, tenascin-like protein extracted from the Porifera Oscarella tuberculata (Homosclerophorida).

A six-armed complex could be extracted from the marine sponge Oscarella tuberculata by a two-step incubation, first in Tris-buffered saline containing EDTA, then in Tris-buffered saline containing urea. The crude extracts contained, in addition, collagen fibrils with surface filaments, individual filaments resembling collagen molecules, and laminin/nidogen-like complexes. The extracts were subsequently purified by gel-filtration chromatography and low-pressure ion-exchange chromatography on DEAE-cellulose, then analyzed by SDS/PAGE and immunoblotting methods. A glycoprotein of high molecular mass was isolated, and reduced to subunits of 230 kDa. After transfer to nitrocellulose, both the complex and its subunits were faintly stained by antibodies against amphibian tenascin. Electron microscopy of the purified extracts demonstrated the presence of a large population of tenascin-like molecules and complexes of several molecules interacting with each other by their central globule.

A simple method for the characterization of photoproducts from DNA applied to the cis-syn thymine dimer.

A method for the unambiguous characterization of DNA photoproducts has been developed. It does not require radio-labelled DNA, or specialized techniques. In the preliminary step, UV-irradiated DNA is hydrolysed to its constituent bases and photoproducts. The photoproducts are then separated from nucleic acid bases using low pressure ion-exchange chromatography on a Dowex 1 x 8 200-400, and an Amberlite CG-50-H+ column. Further separation and purification of photoproducts is carried out on the HPLC Whatman Partisil ODS2 column, using 15% MeOH. The procedure is simple, reproducible and versatile.

High-performance liquid chromatography of proteins : Purification of plant enzymes by ion-exchange chromatography

High-performance liquid chromatography (HPLC) was used to purify catalytically-active enzymes present in minor quantities in plant material. The three O-methyltransferases (S-adenosyl- l-methionine:catechol O-methyltransferases, E.C. 2.1.1.6) of tobacco leaves were subjected to high-performance ion-exchange chromatography. Excellent recovery of enzyme activity (70–100%) was obtained. HPLC was tentatively used at both analytical and preparative scales. As an analytical tool HPLC offered major advantages over conventional low-pressure ion-exchange chromatography in both speed and resolving power. For preparative purposes however, pre-purification of plant extracts by conventional means was necessary before HPLC. Purification achieved by HPLC was evidenced by electrophoretical analysis of the active fractions on sodium dodecyl sulphate—polyacrylamide slab gels.