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Applied Biochemistry and Biotechnology - 相似文献
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Enzymatically digested kappa (A-G4S)-carrageenans, apart from their biological activities in plants, could be used as 'model' molecules to elucidate potential problems in nuclear magnetic resonance spectroscopy of carrageenans. Thus, oligosaccharides obtained from kappa-carrageenan by enzymatic digestion using kappa-carrageenase have been separated on silica and polymeric based ion-exchange and porous graphitic carbon (PGC) columns, coupled to an evaporative light scattering detector. Oligomers were separated on ion-exchange columns using a gradient of ammonium acetate as a developing ion, while analysis on PGC column presented an additional adjacent peak next to each main one, using a gradient of ammonium acetate in water/acetonitrile as a mobile phase. The phenomenon can be attributed to different retention mechanisms that govern the PGC surface. Furthermore, it has been demonstrated that acetonitrile can regulate the selectivity between the peaks raising hopes for preparative chromatography. 相似文献
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A numerical method is proposed for detecting resonances of conservative maps which reduces this task to an optimization problem. We then solve this problem using evolutionary algorithms, which are methods for global optimization inspired by biological evolution. The proposed methodology is simple and can be easily applied to maps of arbitrary dimensions. In this Letter we apply it to several examples of 2- and 4-dimensional conservative maps, with quite promising results concerning integrability, the location of resonances and the presence of chaotic regions surrounding the island chains that correspond to these resonances. 相似文献
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Enzymatically digested oligo-iota-carrageenans were separated with liquid chromatography, coupled to evaporative light scattering detection. As expected, compared to oligo-kappa-carrageenans, the additional sulphate group in the neocarrabiose unit of iota-carrageenans significantly modified the separation mechanisms on ion-exchange chromatography, porous graphitic carbon and ion-pair chromatography. The oligomers were then isolated and characterised off-line with electrospray ionisation mass spectrometry in positive-ion mode. The tetrasaccharide, hexasaccharide and octasaccharide that were identified were associated with protonated heptylamine molecules whose number depended on the number of sulphate groups. 相似文献
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Antonopoulos A Bonnet P Botek E Debrun JL Hakim B Herbreteau B Morin-Allory L 《Rapid communications in mass spectrometry : RCM》2003,17(2):122-125
The mechanism of attachment of Na(+) on glucose, methyl-alpha-D-glucose, methyl-beta-D-glucose, 3-O-methylglucose, tetra-O-methylglucose, and also on galactose and methyl-beta-D-galactose, was studied. For this we measured the ion yields for the complex [sugar-Na(+)] formed by ionisation by matrix-assisted laser desorption/ionisation (MALDI) and ionspray. These data were compared with the relative volatilities and hydrophobicities of the sugars, measured by evaporative light scattering and reversed-phase liquid chromatography, respectively. Some formation enthalpies for the complexes [sugar-Na(+)], starting from the sugar and the cation, were obtained by ab initio calculations. No simple correlations could be observed between the ion yields and the parameters studied, so that the cationisation mechanism of the sugars remains unclear. 相似文献
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Koster S Duursma MC Boon JJ Nielen MW de Koster CG Heeren RM 《Journal of mass spectrometry : JMS》2000,35(6):750-759
In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (5 Weeks journals - Search completed at 22nd. Mar 2000) 相似文献
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