| 1. |
- Gottschalk, Ingo, et al.
(författare)
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Improved lectin-mediated immobilization of human red blood cells in superporous agarose beads
- 2003
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Ingår i: Journal of chromatography. B. - 1570-0232 .- 1873-376X. ; 784:1, s. 203-208
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Tidskriftsartikel (refereegranskat)abstract
- A new type of agarose bead, superporous agarose, was used as a gel support for immobilization of human red blood cells (RBCs) mediated by wheat germ lectin. The number of immobilized cells was similar to that obtained with commercial wheat germ lectin–agarose but the cell stability appeared to be superior. This allowed improved frontal affinity chromatographic analyses of cytochalasin B (CB)-binding to the glucose transporter GLUT1 which established a ratio of one CB-binding site per GLUT1 dimer for both plain RBCs or those treated with different poly amino acids. The measured dissociation constants, 70±14 nM for CB and 12±3 mM for glucose binding to GLUT1, are similar to those reported earlier.
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| 2. |
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| 3. |
- Amini, Nahid, et al.
(författare)
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Feasibility of an on-line restricted access material/liquidchromatography/tandem mass spectrometry method in the rapid and sensitive determination of organophosphorustriesters in human blood plasma
- 2003
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Ingår i: Journal of chromatography. B. - 1570-0232 .- 1873-376X. ; 795:2, s. 245-256
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Tidskriftsartikel (refereegranskat)abstract
- A rapid on-line solid phase extraction/liquid chromatography/tandem mass spectrometry (SPE/LC/MS/MS) method usingrestricted access material (RAM) was developed for the simultaneous determination of eight organophosphorus triesters inuntreated human blood plasma. In a process involving column-switching techniques, the analytes were enriched on the RAMcolumn, separated using a C-18 analytical column and detected with LC/MS. Tandem mass spectrometrywas used to characterizeand quantify the analytes. To elucidate the fragmentation pathway of a number of the analytes, MS3 experiments using an iontrap mass spectrometer were performed. The matrix effects associated with using APCI and ESI interfaces were investigated.The recoveries obtained were in the range 60–92% (R.S.D. < 6%), with estimated detection limits between 0.2 and 1.8 ng/mlof plasma, and the total analysis time was 27 min.
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| 4. |
- Bergström, Sara K., et al.
(författare)
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On-line coupling of microdialysis to packed capillary column liquid chromatography-tandem mass spectrometry demonstrated by measurement of free concentrations of ropivacaine and metabolite from spiked plasma samples
- 2002
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Ingår i: Journal of chromatography. B. - 1570-0232 .- 1873-376X. ; 775:1, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- An on-line coupling of microdialysis to a packed capillary column switching liquid chromatographic system (0.2 mm I.D.) and mass spectrometric detection was developed. The microdialysates were collected in the loop of the first of three valves, coupled in direct series. A deuterated internal standard was added on-line by the middle valve and the third valve operated both a pre-column, for desalting of the physiological buffer used in the sampling procedure, and a separation column. The on-line system was used to study free concentrations of ropivacaine and its metabolite (PPX) in human plasma samples. The analytes were detected by electrospray ionization in a tandem mass spectrometer operating in multiple reaction monitoring mode. The free fractions of ropivacaine (200 nM total concentration) and PPX (20 nM total concentration) in spiked plasma samples were 12±3 and 47±5% (±standard deviation for day-to-day variations, n=3), respectively.
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| 5. |
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| 6. |
- Eriksson, Kåre, et al.
(författare)
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Quantification of melatonin in human saliva by liquid chromatography-tandem mass spectrometry using stable isotope dilution
- 2003
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Ingår i: Journal of chromatography. B. - : Elsevier. - 1570-0232 .- 1873-376X. ; 794:1, s. 115-123
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Tidskriftsartikel (refereegranskat)abstract
- A method for the determination of melatonin in human saliva has been developed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS). Saliva was collected in plastic tubes. 7-D-Melatonin was added as internal standard and the samples were cleaned and concentrated by solid-phase extraction. The limit of detection was 1.05 pg x ml(-1) and the limit of quantification was 3.0 pg x ml(-1). The accuracy of the method was +/-14% at 5.60 pg x ml(-1) and +/-9% at 19.6 pg x ml(-1). The precision was +/-13% at 6.18 pg x ml(-1) and +/-11% at 31.2 pg x ml(-1), respectively. Our HPLC-MS-MS method shows a high sensitivity and specificity for melatonin and more reliable results compared with a radioimmunoassay. The chromatographic method has been used to determine the circadian rhythm of melatonin among three nurses working the night shift and a patient suffering from an inability to fall asleep at night.
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| 7. |
- Foyn Bruun, Cathrine, 1959-
(författare)
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Enrichment of serum amyloid proteins by hydrophobic interaction chromatography combined with two-dimensional electrophoresis with immobilised pH gradients
- 2003
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Ingår i: Journal of chromatography. B. - 1570-0232 .- 1873-376X. ; 790:1-2, s. 355-363
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Tidskriftsartikel (refereegranskat)abstract
- Serum amyloid A protein was subjected to one-step octyl-Sepharose extraction in three different dimensions. Elution was performed partly without UV recording, and with urea or guanidine-based buffers. The eluent was applied directly to denaturing two-dimensional electrophoresis with immobilised pH gradient, or octyl-Sepharose extracted fractions were pooled and lyophilised before application. Proteins were characterised by N-terminal analysis or mass spectrometry. In most of the species that were studied, previously undescribed serum amyloid proteins were detected. Compared to conventional strategies, the presented techniques are more rational and yield more comprehensive information. The presented data also provide a basis for novel perspectives regarding certain inflammatory conditions.
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| 8. |
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| 9. |
- Jansson, Britt, et al.
(författare)
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Simultaneous enantiospecific separation and quantitation of mephenytoin and its metabolites nirvanol and 4'-hydroxymephenytoin in human plasma by liquid chromatography.
- 2003
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Ingår i: Journal of chromatography. B, Analytical technologies in the biomedical and life sciences. - 1570-0232 .- 1873-376X. ; 791:1-2, s. 179-91
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Tidskriftsartikel (refereegranskat)abstract
- A high-performance liquid chromatographic method for the enantiospecific quantitation of S- and R-mephenytoin and its metabolites S- and R-nirvanol and S- and R-4'-hydroxymephenytoin in plasma is described. The compounds were separated using a reversed-phase C(2) column in tandem with a chiral alpha(1)-acid glycoprotein column and were detected using ultraviolet detection at 205 nm. The lower limit of quantification was 10 ng/ml for all compounds using 0.5 ml human plasma (intra-day coefficient of variation <13%, accuracy <+/-20%). The method was validated for human plasma in the concentration range 10-2000 ng/ml for each of the six compounds. The method allows for the simultaneous characterisation of the metabolic capacity of two human drug-metabolising enzymes, CYP2C19 and CYP2B6, and may be used when investigating polymorphisms or changes in activity of these two enzymes.
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| 10. |
- Lutz, Mareike, 1967-, et al.
(författare)
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Monolithic silica rod liquid chromatography with ultraviolet or fluorescence detection for metabolite analysis of cytochrome P450 marker reactions
- 2002
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Ingår i: Journal of chromatography. B. - Amsterdam : Elsevier. - 1570-0232 .- 1873-376X. ; 780:2, s. 205-215
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Tidskriftsartikel (refereegranskat)abstract
- In vitro cytochrome P450 assays are used in metabolism studies in support of early phases of drug discovery to investigate, e.g., metabolic stability, enzyme inhibition and induction by new chemical entities. LC-UV and LC-fluorescence are traditional analytical tools in support of such studies. However, these tools typically comprise different methods of relatively low throughput for the various metabolites of probe reactions. In recent years, LC-MS methods have been developed to increase throughput. Increased throughput can also be achieved by means of modern chromatographic tools in combination with UV and fluorescence detection. This approach is especially suitable when cytochrome P450 isoforms are investigated by means of single probe incubations. Here, an LC-UV/fluorescence system based on a monolithic porous silica column is described for the analysis of metabolites of nine cytochrome P450 marker reactions [phenacetin to paracetamol (CYP1A2), coumarin to 7-hydroxycoumarin (CYP2A6), paclitaxel to 6alpha-hydroxypaclitaxel (CYP2C8), diclofenac to 4-hydroxydiclofenac (CYP2C9), mephenytoin to 4-hydroxymephenytoin (CYP2C19), bufuralol to 1-hydroxybufuralol (CYP2D6), chlorzoxazone to 6-hydroxychlorzoxazone (CYP2E1), midazolam to 1-hydroxymidazolam (CYP3A4), and testosteron to 6beta-hydroxytestosteron (CYP3A4)]. While offering sensitivities and linear ranges comparable to previously reported methods, the set-up described here provides ease of use and increased throughput with maximum cycle times of 4.5 min. © 2002 Elsevier Science B.V. All rights reserved.
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