| 1. |
- Kang, J, et al.
(författare)
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Total chemical synthesis and NMR characterization of the glycopeptide tx5a, a heavily post-translationally modified conotoxin, reveals that the glycan structure is alpha-D-Gal-(1 -> 3)-alpha-D-GalNAc
- 2004
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 271:23-24, s. 4939-4949
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Tidskriftsartikel (refereegranskat)abstract
- The 13-amino acid glycopeptide tx5a (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* = 6-bromotryptophan and Thr* = Gal-GalNAc-threonine), isolated from Conus textile, causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationally modified residues: four cysteine residues, two gamma-carboxyglutamic acid residues, and one residue each of 6-bromotryptophan, 4-trans-hydroxyproline and glycosylated threonine. The chemical nature of each of these has been determined with the exception of the glycan linkage pattern on threonine and the stereochemistry of the 6-bromotryptophan residue. Previous investigations have demonstrated that tx5a contains a disaccharide composed of N-acetylgalactosamine (GalNAc) and galactose (Gal), but the interresidue linkage was not characterized. We hypothesized that tx5a contained the T-antigen, beta-D-Gal-(1-->3)-alpha-D-GalNAc, one of the most common O-linked glycan structures, identified previously in another Conus glycopeptide, contalukin-G. We therefore utilized the peracetylated form of this glycan attached to Fmoc-threonine in an attempted synthesis. While the result-ing synthetic peptide (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp* =6-bromotryptophan and Thr* = beta-D-Gal-(1-->3)-alpha-D-GalNAc-threonine) and the native peptide had almost identical mass spectra, a comparison of their RP-HPLC chromatograms suggested that the two forms were not identical. Two-dimensional H-1 homonuclear and C-13-H-1 heteronuclear NMR spectroscopy of native tx5a isolated from Conus textile was then used to determine that the glycan present on tx5a indeed is not the aforementioned T-antigen, but rather alpha-D-Gal-(1-->3)-alpha-D-GalNAc.
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| 2. |
- Gharizadeh, Baback, et al.
(författare)
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Identification of medically important fungi by the Pyrosequencing (TM) technology
- 2004
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Ingår i: Mycoses. - : Wiley. - 0933-7407 .- 1439-0507. ; 47:1-2, s. 29-33
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Tidskriftsartikel (refereegranskat)abstract
- The Pyrosequencing(TM) technology was used for identification of different clinically relevant fungi. The tests were performed on amplicons derived from the 18S rRNA gene using polymerase chain reaction (PCR) universal primers for amplification. Sequencing was performed up to 40 bases in a variable region with a designed general sequencing primer and the Pyrosequence data were analyzed by BLAST sequence search in the GenBank database. DNA from a total of 21 fungal specimens consisting of nine strains of clinically relevant fungi and 12 clinical specimens from patients suffering from proven invasive fungal infections were PCR-amplified and analyzed by gel electrophoresis, PCR-enzyme-linked immunosorbent assay (ELISA) and the Pyrosequencing technology. All data obtained by the Pyrosequencing technology were in agreement with the results obtained by PCR-ELISA using species/genus-specific oligonucleotides and were as well in accordance with the culture results. The results demonstrate that the Pyrosequencing method is a reproducible and reliable technique for identification of fungal pathogens.
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| 5. |
- Barri, Thaer, et al.
(författare)
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Miniaturized and automated sample pretreatment for determination of PCBs in environmental aqueous samples using an on-line microporous membrane liquid-liquid extraction-gas chromatography system
- 2004
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 76:7, s. 1928-1934
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Tidskriftsartikel (refereegranskat)abstract
- A new, fast, and automated sample pretreatment technique for determination of lipophilic organic compounds in aqueous samples has been developed and applied to the determination of polychlorinated biphenyls (PCBs) in environmental river water. It is based on miniaturized microporous membrane liquid-liquid extraction coupled on-line to gas chromatography (GC) with electron capture detection. The heart of the system that simultaneously connects the sample pretreatment step to the final GC analysis has been named the extracting syringe (ESy). The ESy carries a miniaturized membrane extraction card attached to an electrically and mechanically designed installment and is mounted directly over a GC injector for fully automated injection of the extract. A method was developed to extract 10 PCB congeners from 1-mL water samples (after addition of 40% acetonitrile) with an extraction time of 10 min. The optimized methodology showed good linearity (in the dynamic concentration range of 5 ng L-1-1 mug L-1), enrichment factors of 33-40 times, repeatable extractions (RSD 2-5%, n = 4), a
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| 11. |
- Norberg, J, et al.
(författare)
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Molecular dynamics applied to nucleic acids
- 2002
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Ingår i: Accounts of chemical research. - : American Chemical Society (ACS). - 0001-4842 .- 1520-4898. ; 35:6, s. 465-472
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Tidskriftsartikel (refereegranskat)
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| 12. |
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| 13. |
- Norberg, J, et al.
(författare)
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Supported liquid membrane extraction of urinary trans, trans-muconic acid, a biomarker for benzene exposure
- 2002
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Ingår i: Journal of Separation Science. - 1615-9314. ; 25:5-6, s. 351-355
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Tidskriftsartikel (refereegranskat)abstract
- In this study, sample preparation of urinary trans, trans-muconic acid (tt-MA), a minor metabolite and biomarker of benzene, by means of Supported Liquid Membrane (SLM) extraction has been investigated. The sample extract was automatically transferred on-line to an ion exchange chromatographic column and the analytes were detected using a photodiode array detector. Automation of the system was accomplished using a robotic sample preparation processor integrated into the chromatographic system. Detection limits calculated from the baseline noise was in the sub-ppb range, and quantification of tt-MA is safe down to 10 ppb.
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| 16. |
- Norberg, Å, et al.
(författare)
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Role of variability in explaining ethanol pharmacokinetics : Research and forensic applications
- 2003
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 42:1
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Tidskriftsartikel (refereegranskat)abstract
- Variability in the rate and extent of absorption, distribution and elimination of ethanol has important ramifications in clinical and legal medicine. The speed of absorption of ethanol from the gut depends on time of day, drinking pattern, dosage form, concentration of ethanol in the beverage, and particularly the fed or fasting state of the individual. During the absorption phase, a concentration gradient exists between the stomach, portal vein and the peripheral venous circulation. First-pass metabolism and bioavailability are difficult to assess because of dose-, time- and flow-dependent kinetics. Ethanol is transported by the bloodstream to all parts of the body. The rate of equilibration is governed by the ratio of blood flow to tissue mass. Arterial and venous concentrations differ as a function of time after drinking. Ethanol has low solubility in lipids and does not bind to plasma proteins, so volume of distribution is closely related to the amount of water in the body, contributing to sex- and age-related differences in disposition. The bulk of ethanol ingested (95-98%) is metabolised and the remainder is excreted in breath, urine and sweat. The rate-limiting step in oxidation is conversion of ethanol into acetaldehyde by cytosolic alcohol dehydrogenase (ADH), which has a low Michaelis-Menten constant (Km) of 0.05-0.1 g/L. Moreover, this enzyme displays polymorphism, which accounts for racial and ethnic variations in pharmacokinetics. When a moderate dose is ingested, zero-order elimination operates for a large part of the blood-concentration time course, since ADH quickly becomes saturated. Another ethanol-metabolising enzyme, cytochrome P450 2E1, has a higher Km (0.5-0.8 g/L) and is also inducible, so that the clearance of ethanol is increased in heavy drinkers. Study design influences variability in blood ethanol pharmacokinetics. Oral or intravenous administration, or fed or fasted state, might require different pharmacokinetic models. Recent work supports the need for multicompartment models to describe the disposition of ethanol instead of the traditional one-compartment model with zero-order elimination. Moreover, appropriate statistical analysis is needed to isolate between- and within-subject components of variation. Samples at low blood ethanol concentrations improve the estimation of parameters and reduce variability. Variability in ethanol pharmacokinetics stems from a combination of both genetic and environmental factors, and also from the nonlinear nature of ethanol disposition, experimental design, subject selection strategy and dose dependency. More work is needed to document variability in ethanol pharmacokinetics in real-world situations.
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