| 1. |
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| 2. |
- Anderot, Maria, et al.
(författare)
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Determination of dissociation constants between polyelectrolytes and proteins by affinity capillary electrophoresis
- 2009
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 877:10, s. 892-896
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Tidskriftsartikel (refereegranskat)abstract
- In this manuscript we report the binding affinity between two model proteins, human serum albumin (HSA) and ribonuclease A (RNase A), and negatively charged polyelectrolytes, two different heparin fractions and dextran sulfate, by means of partial filling and affinity capillary electrophoresis. The apparent dissociation constants, K-d, obtained by use of the partial-filling method, between HSA and heparin (17 kDa), heparin (3 kDa) and dextran sulfate (8 kDa) were 33 and 307 mu M, respectively. A new method was developed to determine affinities that take in account different migration directions between the protein and the polyelectrolyte, which was required to study RNase A. By use of this affinity capillary electrophoresis two K-d values were observed for the interaction between RNase A and heparin 17 kDa, yielding a high affinity binding with K-d1 0.0075 mu M, and a lower affinity binding with K-d2 8.7 mu M. For dextran sulfate 8 kDa these K-d values were 0.027 and 10.4 mu M, respectively. Heparin 3 kDa only showed a single K-d value of 0.52 mu M. The results show that the magnitude of the binding affinity depends on the type of polyelectrolyte and its molecular weight. (C) 2009 Elsevier B.V. All rights reserved.
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| 3. |
- Arvidsson, Björn, et al.
(författare)
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Online capillary solid phase extraction and liquid chromatographic separation with quantitative tandem mass spectrometric detection (SPE-LC-MS/MS) of ximelagatran and its metabolites in a complex matrix.
- 2009
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 877:3, s. 291-297
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the development and validation of a fully automated quantitative analysis method of melagatran, its prodrug ximelagatran, and its major metabolites for the study of drug behavior in biofluids. The method involves online sample clean-up and enrichment on a C4 capillary column followed by separation on a capillary C18 column. Electrospray ionization tandem mass spectrometric detection in positive ion mode was performed with multiple reactions monitoring of eight different transients, divided into two time segments with four transients each. The structural similarity, the complexity of the matrix (pig liver extract) and the formation of isobaric fragment ions, made efficient chromatographic separation necessary. The analysis method provides valid accuracy (<9%; RSD%), precision (<8%; RSD%), linearity (<1.2 nM–1 μM; R2 > 0.999), limit of quantitation (<3.6 nM), retention repeatability (<1.2%; RSD%), selectivity, as well as analyte and column stabilities over a wide concentration range.
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| 4. |
- Bennemo, Mia, et al.
(författare)
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A chromatographic method for determination of supercoiled plasmid DNA concentration in complex solutions.
- 2009
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 877:24, s. 2530-6
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Tidskriftsartikel (refereegranskat)abstract
- A method for determination of the plasmid DNA concentration with subsequent analysis of the ratio supercoiled to open circular form is presented. The method is suitable for samples from all steps of the manufacturing process, from fermentation to final product. The analysis consists of size exclusion chromatography, followed by analytical thiophilic aromatic chromatography. In the first step, the plasmid DNA concentration is determined by group separation, including removal of RNA and other impurities, within less than 2 min. The limit of detection and quantification was 0.28 and 0.83 microg/ml, respectively. The precision of the method is high, providing a coefficient of variation as low as below 2%. In the second step, the ratio of open circular to supercoiled plasmid DNA is determined following separation of the two plasmid DNA isoforms with a linear salt gradient. The precision of the second step was evaluated using serial injections of aliquots of a sample stock solution. In comparison with the two most commonly used methods, the developed analysis was found to be significantly more accurate than agarose gel electrophoresis and equivalent to capillary gel electrophoresis. The combined methods for quantification and control of homogeneity of plasmid DNA presented here enable reliable and precise analysis at all steps of the manufacturing process.
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| 5. |
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| 6. |
- Chadt, J, et al.
(författare)
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Monitoring of dimethyl sulphate-induced N3-methyladenine, N7-methylguanine and O6-methylguanine DNA adducts using reversed-phase high performance liquid chromatography and mass spectrometry
- 2008
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 867, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- This work describes the determination of N3-methyladenine, N7-methylguanine and O6-methylguanine adducts in dimethyl sulphate-treated salmon-testes DNA employing reversed-phase high performance liquid chromatography (RP-HPLC) with UV–vis detection, followed by mass-spectrometric verification using electrospray ionisation in positive mode ESI(+). Within validation parameters, accuracy, precision, calibration parameters, limit of detection (LOD) and quantitation (LOQ) as well as stability of standard stock solutions were tested and presented for UV/vis detection. The limit of detection (LOD) was found to be 0.1 ng/mL for N3-methyladenine and 0.2 ng/mL for both N7-methylguanine and O6-methylguanine (S/N = 3). The limit of quantitation (LOQ) was found to be 0.5 ng/mL for all measured compounds, (S/N = 10). Quantitative results were obtained for each substance based on eight-point calibration. Intra- and inter-day precisions were within 1.73–6.96 and 2.26–7.58%, respectively, and correlation coefficients of calibration curves (R2) ranged from 0.9992 to 0.9997. Relative proportion of N7-methylguanine was accounted for 61.53 ± 2.97% (R.S.D. = 4.8), N3-methyladenine for 38.19 ± 2.99% (R.S.D. = 9.6) and O6-methylguanine for 0.29 ± 0.02% (R.S.D. = 5.1), respectively. The application of the above-mentioned techniques provides a valuable contribution for simultaneous determination of methylated DNA adducts, and may represent a suitable approach for similar monitoring/screening studies.
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| 7. |
- Claeson Bohnstedt, Kristina, et al.
(författare)
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Porous graphitic carbon chromatography-tandem mass spectrometry for the detection of isoprostanes in human cerebrospinal fluid
- 2005
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 827:1, s. 39-43
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Tidskriftsartikel (refereegranskat)abstract
- F2-isoprostanes are produced by the non-enzymatic peroxidation of arachidonic acid in membrane phospholipids. This paper describes a new method for the determination of all four classes of F2-isoprostanes in human cerebrospinal fluid (CSF) involving separation on a 1 mm × 150 mm porous graphitic carbon (PGC) column and detection by triple quadrupole mass spectrometry in negative-ion electrospray mode. The sample pre-treatment consisted of an ultrafiltration step, following which 300 μl of CSF sample could be injected directly onto a 1 mm × 10 mm PGC guard column functioning as a trap for the analytes. The loading solvent was Milli-Q water at 125 μl/min. After 3 min, the sample was switched into the separation column. The F2-isoprostanes were separated in 20 min using a linear solvent gradient comprising water, methanol, acetonitrile and ammonium hydroxide at a pH of 9.5 and a flow of 50 μl/min The limit of detection (calculated as 3S/N) was approximately 40 pM (14 pg/ml). The assay was linear within the examined range (18–450 pg/ml), using CSF spiked with iPF2α-III standard (r2 > 0.995). Repeatability data were calculated for CSF spiked to 90 pg/ml and the relative standard deviation (RSD) obtained was 3% (n = 6).
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| 8. |
- Dorlo, Thomas P C, et al.
(författare)
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Development and validation of a quantitative assay for the measurement of miltefosine in human plasma by liquid chromatography-tandem mass spectrometry.
- 2008
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 865:1-2, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the quantification of miltefosine is presented. A 250 microL human EDTA plasma aliquot was spiked with miltefosine and extracted by a solid-phase extraction method. Separation was performed on a Gemini C18 column (150 mm x 2.0 mm I.D., 5 microm) using an alkaline eluent. Detection was performed by positive ion electrospray ionization followed by triple-quadrupole mass spectrometry. The assay has been validated for miltefosine from 4 to 2000 ng/mL using 250 microL human EDTA plasma samples. Results from the validation demonstrate that miltefosine can be accurately and precisely quantified in human plasma. At the lowest level, the intra-assay precision was lower than 10.7%, the inter-assay precision was 10.6% and accuracies were between 95.1 and 109%. This assay is successfully used in a clinical pharmacokinetic study with miltefosine.
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| 9. |
- Fotoohi, K, et al.
(författare)
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Interference of 7-hydroxymethotrexate with the determination of methotrexate in plasma samples from children with acute lymphoblastic leukemia employing routine clinical assays
- 2005
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Ingår i: Journal of Chromatography. B. - : Elsevier BV. - 1873-376X .- 1570-0232. ; 817:2, s. 139-144
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy of two clinical assays, the enzyme-multiplied immunoassay (EMIT) and fluorescence polarization immunoassay (FPIA2), universally employed for measurement of plasma levels of methotrexate (MTX) in children administered a high dose of this drug for treatment of acute lymphoblastic leukemia was evaluated here. Because of its superior specificity, sensitivity, and precision, high performance liquid chromatography (HPLC) was selected as the reference method with which the other two procedures were compared using approximately 420 different plasma samples for method comparison. 7-Hydroxymethotrexate (7-OHMTX), the major plasma metabolite of MTX, that can be detected in plasma at relatively high concentrations for long periods following infusion of a high dose of MTX, was also quantitated by HPLC. Forty-two and 66 h after infusion, the plasma level of MTX was overestimated in 2% and 3% of the samples by the FPIA2 procedure in 5% and 31% by the EMIT assay. The overall correlation coefficients (r(2)) for the values obtained by FPIA2 or EMIT versus those based on HPLC were 0.989 and 0.663, respectively. The presence of 7-OHMTX exerted a highly significant influence (p = 0.0007 as determined by the unpaired t-test) on MTX measurement by the EMIT assay. We conclude that the rapid automated procedures routinely used at present and in particular EMIT, suffer from cross-reactivity with metabolites of MTX. Thus, the relatively high percentage of samples in which the level of MTX is overestimated at check-points by EMIT may result in longer periods of hospitalization, higher costs and prolonged administration of elevated doses of "rescue" leucovorin with an increased risk for relapse.
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| 10. |
- Garscha, Ulrike, et al.
(författare)
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Enantiomeric separation and analysis of unsaturated hydroperoxy fatty acids by chiral column chromatography-mass spectrometry
- 2008
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Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 872, s. 90-98
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Tidskriftsartikel (refereegranskat)abstract
- Hydroperoxides of 18:2n-6 and 20:4n-6 were obtained by autoxidation and photooxidation. The enantiomers Were separated as free acids (Reprosil Chiral-NR column, eluted with hexane containing 1-1.2% alcoholic modifier) and analyzed by on line UV detection (234 nm) and liquid chromatography-MS/MS/MS of carboxylate anions (A(-) -> (A(-)-18) -> full scan) in an ion trap. The combination of UV and MS/MS/MS analysis facilitated identification of hydroperoxides even in complex mixtures of autoxidized or photooxidized fatty acids. The signal intensities increased about two orders of magnitude by raising the isolation width of A(-) from 1.5 amu to 5 or 10 amu for cis-trans conjugated hydroperoxy fatty acids, and one order of magnitude of more for non-conjugated hydroperoxy fatty acids. The S enantiomer of 8-, 9-, 10-, and 13-hydroperoxyoctadecadienoic acids and the S enantiomer of cis-trans conjugated hydroperoxyeicosatetraenoic acids eluted before the corresponding R enantiomer with two exceptions (11-hydroperoxylinoleic acid and 8-hydroperoxyeicosa-5Z,9E,11Z,14Z-tetraenoic acid). The separation of enantiomers or regioisomers could be improved by the choice of either isopropanol or methanol as alcoholic modifier.
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