| 1. |
- Bal, Karol, et al.
(författare)
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New and simple procedure for the determination of muramic acid in chemically complex environments by gas chromatography-ion trap tandem mass spectrometry
- 2000
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Ingår i: Journal of Chromatography. B. - 1387-2273. ; 738:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- A gas chromatographic-ion trap tandem mass spectrometric method was developed for the quantification of muramic acid, a marker of bacterial peptidoglycan, in environmental and clinical specimens. Samples (bacteria, house dust and urine) were heated in methanolic hydrochloric acid overnight and extracted with hexane for removal of hydrophobic compounds. The aqueous phase was evaporated and heated in acetic anhydride and pyridine after which the product, the acetate derivative, was washed with dilute hydrochloric acid and water. The described method is both rapid and simple to apply, and produces a stable derivative. It should become widely used for measuring peptidoglycan in chemically complex environments.
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| 2. |
- Barinaga-Rementeria Ramírez, Irene, et al.
(författare)
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Affinity partitioning of biotinylated mixed liposomes: effect of charge on biotin-NeutrAvidin interaction
- 2000
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Ingår i: Journal of Chromatography. B. - 1387-2273. ; 743:1-2, s. 389-396
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Tidskriftsartikel (refereegranskat)abstract
- The partitioning behaviour of biotinylated mixed liposomes in aqueous poly(ethylene glycol)/dextran two-phase systems containing NeutrAvidin-dextran suggests that the biotin-NeutrAvidin affinity interaction is charge dependent. Biotinylated phosphatidylcholine liposomes with a low negative surface charge distributed in the NeutrAvidin-containing bottom phase at neutral pH, but the introduction of additional negative charges by including phosphatidylserine or the surfactant sodium dodecylsulfate in the liposomes caused them to distribute in the poly(ethylene glycol)-rich top phase instead. By gradually lowering the pH of the affinity two-phase system below the isoelectric point (6.3) of NeutrAvidin, negatively charged phosphatidylserine/phosphatidylcholine liposomes increasingly were attracted by NeutrAvidin to the bottom phase. It is suggested that acidic amino acids present at the rim of the biotin-binding pocket of NeutrAvidin may interact electrostatically with charged residues of the closely apposed liposome surface affecting the affinity interaction.
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| 3. |
- Berggren, K., et al.
(författare)
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Partitioning of peptides and recombinant protein-peptide fusions in thermoseparating aqueous two-phase systems : effect of peptide primary structure
- 2000
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Ingår i: Journal of Chromatography B. - 0378-4347. ; 743:1-2, s. 295-306
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Tidskriftsartikel (refereegranskat)abstract
- Genetic engineering has been used for fusion of peptides, with different length and composition, on a protein to study the effect on partitioning in an aqueous two-phase system. The system was composed of dextran and the thermoseparating ethylene oxide-propylene oxide random copolymer, EO30PO70. Peptides containing tryptophan, proline, arginine or aspartate residues were fused at the C-terminus of the recombinant protein ZZ-cutinase. The aim was to find effective tags for the lipolytic enzyme cutinase for large-scale extraction. The target protein and peptide tags were partitioned separately and then together in the fusion proteins in order to gain increased understanding of the influence of certain amino acid residues on the partitioning. The salt K2SO4 was used to reduce the charge dependent salt effects on partitioning and to evaluate the contribution to the partition coefficient from the hydrophobic-hydrophilic properties of the amino acid residues. The effect of Trp on peptide partitioning was independent of the difference in primary structure for (Trp)n, (Trp-Pro)n, (Ala-Trp-Trp-Pro)n and was only determined by the number of Trp. The effect of the charged residues, Arg and Asp, was dependent on the surrounding residues, i.e. if they were situated next to Trp or not. The partitioning behaviour observed for the peptides was qualitatively and in some cases also quantitatively the same as for the fusion proteins. The effect of the salts sodium perchlorate and triethylammonium phosphate on the partitioning was also studied. The salt effects observed for the peptides were qualitatively similar to the effects observed for the fusion proteins.
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| 4. |
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| 5. |
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| 6. |
- Carnerup, Martin, et al.
(författare)
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Determination of 5-hydroxy-N-methyl-2-pyrrolidone and 2-hydroxy-N-methylsuccinimide in human plasma and urine using liquid chromatography-electrospray tandem mass spectrometry
- 2001
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Ingår i: Journal of Chromatography. B. - 1387-2273. ; 761:1, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- A method for simultaneous determination of 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) was developed. These compounds are metabolites from N-methyl-2-pyrrolidone (NMP), a powerful and widely used organic solvent. 5-HNMP and 2-HMSI were purified from plasma and urine by solid-phase extraction using Isolute ENV+ columns, and analysed by liquid chromatography coupled to a mass spectrometer fitted with an atmospheric pressure turbo ion spray ionisation interface in the positive ion mode. The method was validated for plasma and urine concentrations from 0.12 to 25 microg/ml. The recoveries for 5-HNMP and 2-HMSI in plasma were 99 and 98%, respectively, and in urine 111 and 106%, respectively. For 5-HNMP and 2-HMSI, the within-day precision in plasma was 1-4 and 3-6%, respectively, and in urine 2-12 and 3-10%, respectively. The corresponding data for the between-day precision was 5 and 3-6%, respectively, and 4-6 and 7-8%, respectively. The detection limit for 5-HNMP was 4 ng/ml in plasma and 120 ng/ml in urine. For 2-HMSI, it was 5 ng/ml in plasma and 85 ng/ml in urine. The method is applicable for analysis of plasma and urine samples from workers exposed to NMP.
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