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C S Creaser

Publications and source records attributed to C S Creaser.

17 recordsLinked to original sources
PubMed2002

Electrospray mass spectrometry for the identification of MHC class I-associated peptides expressed on cancer cells.

Electrospray ionisation (ESI) mass spectrometry (MS) has been used extensively for the detection of peptides presented by major histocompatibility complex (MHC) molecules. This review focuses on the optimisation of electrospray mass spectrometry and the use of tandem mass spectrometry to sequence MHC class I peptides. We review the isolation of MHC class I peptides from the surface of cells with particular reference to tumour cells. In addition, we also discuss the advantages and disadvantages of the methods available to concentrate and fractionate the peptides prior to analysis by electrospray mass spectrometry.

Animals↗
PubMed2001

Direct evidence that leukemic cells present HLA-associated immunogenic peptides derived from the BCR-ABL b3a2 fusion protein.

The BCR-ABL oncogene is central in the pathogenesis of chronic myeloid leukemia (CML). Here, tandem nanospray mass spectrometry was used to demonstrate cell surface HLA-associated expression of the BCR-ABL peptide KQSSKALQR on class I-negative CML cells transfected with HLA-A*0301, and on primary CML cells from HLA-A3-positive patients. These patients mounted a cytotoxic T-lymphocyte response to KQSSKALQR that also killed autologous CML cells, and tetramer staining demonstrated the presence of circulating KQSSKALQR-specific T cells. The findings are the first demonstration that CML cells express HLA-associated leukemia-specific immunogenic peptides and provide a sound basis for immunization studies against BCR-ABL.

Adult↗
PubMed2001

FTIR sensing of inhomogeneous systems using immobilized organometalcarbonyl probe groups.

Tricarbonyl(eta 5-cyclohexadienyl)iron(0) and dicarbonyl(triphenylphosphine)(eta 5-cyclo-hexadienyl)iron(0) were derivatized by attachment of an aminopropylsilyl link and covalently attached to fumed silica particles. The fumed silica was coated onto the ZnSe element of an attenuated total reflection (ATR) cell for Fourier transform infrared (FTIR) spectroscopic analysis. The immobilized organometalcarbonyl probe groups are shown to retain their capacity to function as a key element of a molecular sensor assembly and the nu(CO) bands of the two probe groups were interrogated to calibrate the responses for 0-5% levels of dodecane in cyclohexanol to within +/- 0.1%. The potential for dual sensing is described and the simultaneous monitoring of two discrete regions of a dynamically varying inhomogeneous system is reported for the determination of dodecane in cyclohexanol as solutions mix across a permeable barrier in the ATR cell.

Journal Article↗
PubMed2000

In-membrane preconcentration/membrane inlet mass spectrometry of volatile and semivolatile organic compounds.

The on-line determination of volatile and semivolatile organic compounds (SVOCs) is reported using membrane inlet mass spectrometry with in-membrane preconcentration (IMP-MIMS). Semivolatile organic compounds in aqueous samples are preconcentrated in a flow-through silicone hollow-fiber membrane inlet held in a GC oven. The sample stream is replaced with air, and the SVOCs are thermally desorbed into the mass spectrometer by rapid heating of the membrane. The method is evaluated for the on-line determination of 4-fluorobenzoic acid, 3,5-difluorobenzoic acid, 2-chlorophenol, p-tert-butylphenol, and dimethyl sulfoxide (DMSO) in water. The selectivity of the IMP-MIMS technique for SVOCs in the presence of VOCs is demonstrated. Cryotrapping and a rapid gas chromatographic separation step were added between the membrane and the mass spectrometer ion source for the determination of SVOCs in complex mixtures. The procedure is demonstrated for the determination of dimethyl sulfoxide (DMSO) in equine urine, using internal standardization with DMSO-d6. Full-scan electron ionization (EI) mass spectrometric detection showed good linearity (R = 0.998) and RSDs, relative to the internal standard, of 2.2% for desorption only and 4.6% for desorption and cryotrapping.

Animals↗
PubMed2000

Nano-electrospray and microbore liquid chromatography-ion trap mass spectrometry studies of copper complexation with MHC restricted peptides.

The formation of copper/peptide complex ions by nano-electrospray and microbore HPLC-electrospray mass spectrometry has been investigated for major histocompatibility complex (MHC) class I and class II restricted peptides. Post-column addition of copper(II) acetate following microbore HPLC-MS separation was carried out using a mixing T-piece or via the sheath flow inlet of the electrospray source. Optimal analytical conditions for copper complex ion formation were determined by variation of copper concentration, pH, nebulization gas supply and spray voltage. Tandem mass spectrometry of copper/peptide complex ions provides peptide sequence information and insight into the peptide chelation sites. Copper associated y fragment ions dominate the product ion spectrum for non-histidine containing peptides, but both b and y copper complex ions were observed for the histidine containing MHC class I associated peptide gp70.

Animals↗
PubMed1998

Organometallic flavonoid derivatives as spectroscopic probes.

Derivatives of naringenin have been synthesized with organometalcarbonyl reporting groups for IR spectroscopy attached at C-2, C-3', or C-6, and the products have been tested for the induction of nod gene expression using a Rhizobium leguminosarum strain which contains the Escherichia coli lacZ (beta-galactosidase) gene fused to nodABC. Derivatives with an OMe substituent within the reporting group moiety showed residual gene induction activity.

Escherichia coli↗
PubMed1998

Immunoaffinity chromatography combined on-line with high-performance liquid chromatography-mass spectrometry for the determination of corticosteroids.

On-line coupled immunoaffinity chromatography-reversed-phase high-performance liquid chromatography (IAC-HPLC) with detection by quadrupole ion trap mass spectrometry using a particle beam interface has been developed for the determination of the steroids, dexamethasone and flumethasone. HEMA (polyhydroxyethylmethacrylate) was evaluated as a support material for the anti-dexamethasone antibodies used in IAC. Antibody cross-reactivity and non-specific binding have been investigated for the HEMA bound anti-dexamethasone IAC column. The on-line IAC-HPLC-MS determination of dexamethasone and flumethasone in post-administration equine urine samples showed precisions (R.S.D.) of 8.0 and 7.1%, respectively, with limits of detection in the range 3-4 ng/ml.

Adrenal Cortex Hormones↗
PubMed1997

Validation of a congener specific method for ortho and non-ortho substituted polychlorinated biphenyls in fruit and vegetable samples.

An on-line procedure has been developed and validated for the clean-up and fractionation of ortho and non-ortho-PCBs in fruit and vegetable samples. The procedure combines silica/acid and carbon/glass fibre columns with gas chromatography-mass spectrometry. Chromatography on carbon/glass fibre allowed collection of mono-ortho/di-ortho and non-ortho-PCB fractions, which were determined separately by GC-MS. The method was validated by replicate analyses and by inter-laboratory comparison of data for PCB congeners determined in fruit and vegetable samples collected in South Wales. The concurrent determination of ortho and non-ortho substituted PCBs is reported with recoveries ranging from 55-95% and a mean intra-laboratory precision (%COV) of 9.5% for apple extracts.

Chromatography↗
PubMed1996

Levels of selected ortho and non-ortho polychlorinated biphenyls in UK retail milk.

Nineteen pooled samples of retail cow's milk were analysed for ortho (PCBs 28, 52, 101, 118, 138, 153 and 180) and non-ortho (PCBs 77, 126 and 169) polychlorinated biphenyls. Concentrations of individual congeners in whole milk were in the ranges 2 to 95 ng/kg for ortho substituted PCBs (51 to 2440 ng/kg fat) and 0.05 to 0.6 ng/kg for non-ortho substituted PCBs (1.3 to 15.4 ng/kg fat). These values provide a preliminary estimate of background contamination levels for polychlorinated biphenyls in UK milk. Results expressed in TEQs, using the recently proposed WHO/IPCS TEFs, averaged 0.06 ng TEQ/kg whole milk.

Animals↗
PubMed1992

Modified on-column interface for coupled high-performance liquid chromatography-gas chromatography and its application to the determination of levamisole in milk.

A modified on-column interface is reported for the coupling of high-performance liquid chromatography with gas chromatography, incorporating an adapted, commercially available multidimensional gas chromatography switching system. Novel features include cryogenic analyte focusing, total solvent exclusion from the analytical column and independent carrier gas supplies to the analytical GC column and uncoated pre-column. The instrumentation was used for the determination of the veterinary anthelmintic drug levamisole in milk with analyte detection by both flame ionisation and nitrogen-phosphorus detectors. Detection limits for the assay were 2.2 micrograms l-1 and 0.4 micrograms l-1 by flame ionisation and nitrogen-phosphorus detectors, respectively. The assay was applied to a survey of fourteen milk samples from different dairy outlets.

Animals↗
PubMed1992

On-line high-performance liquid chromatographic/gas chromatographic/tandem ion trap mass spectrometric determination of levamisole in milk.

On-line high-performance liquid chromatography/high-resolution gas chromatography/tandem mass spectrometry, performed on a quadrupole ion trap, has been used as a rapid method for the quantification of the anthelmintic drug levamisole in raw milk extracts following a simple extraction procedure. Detection at the 0.5 p.p.b. level and a linear response in the 10-0.5 p.p.b. range is demonstrated. Multiple-scan monitoring techniques have been used to acquire chemical ionization tandem mass spectra and electron impact mass spectra in a single chromatographic run.

Animals↗
PubMedDate not supplied

PCB and PCDD/DF congeners in locally grown fruit and vegetable samples in Wales and England.

A survey was undertaken of PCB and PCDD/DF congeners in fruit and vegetables grown in an urban areas close to a chemical waste incinerator and three rural locations. All of the concentrations detected were low and there was considerable overlap between those found in urban and rural samples. Some similarities with the congener composition of air samples were identified and concentrations in apple skin were noticeably higher than those in the flesh of the fruit. These results suggest that atmospheric deposition was an important contamination pathway. Assessments using the highest concentrations found indicated that consumption of such fruit and vegetables would represent an additional 3% of the normal dietary intake for PCBs and 8% for PCDD/DFs.

Benzofurans↗
PubMedDate not supplied

PCB and PCDD/DF concentrations in egg and poultry meat samples from known urban and rural locations in Wales and England.

A survey was undertaken of PCB and PCDD/DF congeners in eggs and poultry meat from a smallholding close to a chemical waste incinerator, other sites in the surrounding district, and three rural locations. The concentrations from the site close to the incinerator were appreciably greater than those found elsewhere, although the contrast was less marked for poultry meat than eggs. All types of poultry produce displayed noticeable variations in congener composition when the samples were grouped according to geographical origin. These results support the view that the environment in which poultry live does influence the PCB and PCDD/DF characteristics of their products. Exposure calculations indicated that consumption of eggs from the site close to the incinerator would constitute a substantial proportion of recommended daily intakes for such contaminants and at the present time these products are not being eaten.

Animals↗
PubMedDate not supplied

Development of multi-residue methodology for the HPLC determination of veterinary drugs in animal tissues.

The application of solid-phase extraction and HPLC with UV-diode array detection to the multi-residue determination of veterinary drugs is described. A two-stage SPE clean-up was employed, using C18 and silica cartridges. HPLC analysis was carried out on a base-deactivated C8 column using gradient elution systems at two pH values. The procedure establishes the basis of a method for routine screening of pig kidney samples for some sulphonamides, benzimidazoles, nitroimidazoles and nitrofurans at concentrations at or below the UK Maximum Residue Limits (MRLs). Limits of detection of 2-18 micrograms/kg could be achieved for these analytes at recoveries of 40-70%. UV spectra measured on-line were used for confirmation of peak identities at these concentrations. The possibility of extension of this procedure to a wider range of analyses is discussed.

Animals↗