| 1. |
- Brits, Martin, et al.
(författare)
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Comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry for screening of organohalogenated compounds in cat hair
- 2018
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1536, s. 151-162
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Tidskriftsartikel (refereegranskat)abstract
- The coupling of comprehensive two-dimensional gas chromatography with high-resolution time of-flight mass spectrometry offers the best separation efficiency combined with accurate mass measurements over a wide mass range. The tremendous power of this screening tool is illustrated by trace qualitative screening analysis of organohalogenated compounds (OHCs) in pet cat hair. Tentative identification was supported by mass spectral database searches and elemental formula prediction from the experimentally determined accurate mass data. This screening approach resulted in the first tentative identification of pentabromoethylbenzene, decabromodiphenyl ethane, hexabromocyclododecane, trisbromoneopentyl alcohol, tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl)phosphate in the South African indoor environment. A total of seventy-two OHCs were identified in the samples and include known flame retardants, such as polybrominated diphenyl ethers, and legacy contaminants such as polychlorinated biphenyls and organochlorine, organophosphorous and pyrethroid pesticides. The results obtained from cat hair indicate that these pets are exposed to complex mixtures of OHCs and the detection of these compounds suggests that non-invasive cat hair samples can be used to model indoor exposure with reference to external deposition of OHCs present in the air and dust surrounding people. Toddlers share the same environment as pet cats and therefore also the same health risks.
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| 2. |
- Lowe, Christopher R., et al.
(författare)
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High-performance liquid affinity chromatography of proteins on Cibacron Blue F3G-A bonded silica
- 1981
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Ingår i: Journal of chromatography. A. - 0021-9673. ; 215, s. 303-316
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Tidskriftsartikel (refereegranskat)abstract
- The reactive triazine dye, Cibacron Blue F3G-A, has been covalently attached to microparticulate porous silica and used for the resolution of a number of complementary proteins by high-performance liquid affinity chromatography (HPLAC). Cibacron Blue F3G-A was converted to its 6-aminohexyl derivative by reaction with 1,6-diaminohexane and coupled to γ-glycidoxypropyltrimethoxysilane-activated porous silica (5 μm) to generate an adsorbent containing 5.5–6.7 μmol dye/g silica.Cibacron Blue F3G-A silica columns, in conjunction with on-line monitoring of protein concentration and enzyme activity, may be exploited for the high speed fully automated resolution of dehydrogenases, isoenzymes, kinases and other proteins such as pancreatic ribonuclease A from simple or complex mixtures. The examples demonstrate the versatility of HPLAC on silica-immobilised Cibacron Blue F3G-A.
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| 3. |
- Bylund, Dan, et al.
(författare)
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Chromatographic alignment by warping and dynamic programming as a pre-processing tool for PARAFAC modelling of liquid chromatography-mass spectrometry data
- 2002
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 961:2, s. 237-244
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Tidskriftsartikel (refereegranskat)abstract
- Solutes analysed with LC–MS are characterised by their retention times and mass spectra, and quantified by the intensities measured. This highly selective information can be extracted by multiway modelling. However, for full use and interpretability it is necessary that the assumptions made for the model are valid. For PARAFAC modelling, the assumption is a trilinear data structure. With LC–MS, several factors, e.g. non-linear detector response and ionisation suppression may introduce deviations from trilinearity. The single largest problem, however, is the retention time shifts not related to the true sample variations. In this paper, a time warping algorithm for alignment of LC–MS data in the chromatographic direction has been examined. Several refinements have been implemented and the features are demonstrated for both simulated and real data. With moderate time shifts present in the data, pre-processing with this algorithm yields approximately trilinear data for which reasonable models can be made.
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| 4. |
- Bylund, Dan, et al.
(författare)
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Peak purity assessment in liquid chromatography-mass spectrometry
- 2001
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 915:1/2, s. 43-52
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Tidskriftsartikel (refereegranskat)abstract
- Fixed-size moving window evolving factor analysis and base peak chromatograms have been used for peak purity detection in data generated with LC–MS. The two methods were evaluated with both real and simulated data and were found to be fast and complementary to each other. When a possibly impure peak is detected, it is suggested that further information can be obtained from local principal component analysis modelling and comparative mass chromatogram plots.
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| 5. |
- Carlsson, Mats, et al.
(författare)
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Effects of fused tryptophan rich peptides to a recombinant protein A domain on the partitioning in polyethylene glycol-dextran and Ucon-dextran aqueous two-phase systems
- 1996
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 756:1-2, s. 107-117
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Tidskriftsartikel (refereegranskat)abstract
- Genetic engineering has been used to construct fusion proteins with tryptophan containing peptides. The peptides and the fusion proteins have been partitioned in aqueous two-phase systems of poly(ethylene glycol) (PEG)-dextran and Ucon-dextran. The studied model protein was ZZT0, where Z is an engineered domain of domain B of staphylococcal protein A. The specially designed hydrophobic peptides, Ala-Trp-Trp-Pro (T1) and (Ala-Trp-Trp-Pro)2 (T2), have been inserted into ZZT0, to give the peptide-protein fusions ZZT1 and ZZT2. In the experimental studies it was found that T1 and T2 preferred the PEG phase and even more the Ucon phase over the dextran phase. For T2 the partitioning was more one sided than for T1. For the fusion proteins, ZZT1 and ZZT2, the partitioning was enhanced into the PEG or Ucon rich phase as compared to ZZT0. The effects were lower than expected from independent contributions to the partition coefficient from the protein and the peptides. A heterogeneous lattice model was used to calculate theoretical peptide and protein partition coefficients. The calculations could reproduce the qualitative features of the experimental data. The model results suggest that a part of these experimentally observed effects is due to a depletion zone, i.e. a zone of reduced polymer concentration around the protein. The experimental results indicate a further reduction of the partition coefficient, beyond that predicted by the lattice calculations. A possible folding of the inserted peptide is discussed as a plausible mechanism for this further reduction in the partition coefficient.
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| 6. |
- Svensson, Mårten, et al.
(författare)
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Aqueous two-phase systems containing self-associating block copolymers - Partitioning of hydrophilic and hydrophobic biomolecules
- 1999
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 839:1-2, s. 71-83
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Tidskriftsartikel (refereegranskat)abstract
- A series of proteins and one membrane-bound peptide have been partitioned in aqueous two-phase systems consisting of micelle-forming block copolymers from the family of Pluronic block copolymers as one polymer component and dextran T500 as the other component. The Pluronic molecule is a triblock copolymer of the type PEO-PPO-PEO, where PEO and PPO are poly(ethylene oxide) and poly(propylene oxide), respectively. Two different Pluronic copolymers were used, P105 and F68, and the phase diagrams were determined at 30oC for these polymer systems. Since the temperature is an important parameter in Pluronic systems (the block copolymers form micellar-like aggregates at higher temperatures) the partitioning experiments were performed at 5 and 30oC, to explore the effect of temperature-triggered micellization on the partitioning behaviour. The temperatures correspond to the unimeric (single Pluronic chain) and the micellar states of the P105 polymer at the concentrations used. The degree of micellization in the F68 system was lower than that in the P105 system, as revealed by the phase behaviour. A membrane-bound peptide, gramicidin D, and five different proteins were partitioned in the above systems. The proteins were lysozyme, bovine serum albumin, cytochrome c, bacteriorhodopsin and the engineered B domain of staphylococcal protein A, named Z. The Z domain was modified with tryptophan-rich peptide chains in the C-terminal end. It was found that effects of salt dominated over the temperature effect for the water-soluble proteins lysozyme, bovine serum albumin and cytochrome c. A strong temperature effect was observed in the partitioning of the integral membrane protein bacteriorhodopsin, where partitioning towards the more hydrophobic Pluronic phase was higher at 30oC than at 5oC. The membrane-bound peptide gramicidin D partitioned exclusively to the Pluronic phase at both temperatures. The following trends were observed in the partitioning of the Z protein. (i) At the higher temperature, insertion of tryptophan-rich peptides increased the partitioning to the Pluronic phase. (ii) At the lower temperature, lower values of K were observed for ZT2 than for ZT1.
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| 7. |
- Svensson, Mårten, et al.
(författare)
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Partitioning of hydrophobic amino acids and oligopeptides in aqueous two-phase system containing self-aggregating block copolymer - Effects of temperature, salts and surfactants
- 1997
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Ingår i: Journal of Chromatography A. - 0021-9673. ; 761:1-2, s. 91-101
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Tidskriftsartikel (refereegranskat)abstract
- The partitioning of hydrophobic amino acids and oligopeptides in the Pluronic P105-dextran-water system has been studied. Pluronic P105 is a member of a family of triblock copolymers with the structure PEO-PPO-PEO, where PEO is poly(ethylene oxide) and PPO poly(propylene oxide). The partitioning was studied for tryptophan, phenylalanine and di- and tri-peptides composed of these amino acids at 5 and 40oC. These temperatures correspond to a unimeric (5oC) and a micellar (40oC) state of the P105 molecule. Partitioning depended strongly on the temperature which is attributed to the increased hydrophobicity of Pluronic P105 with increasing temperature. However, it appears that the presence of the micelles plays no major direct role. The effect of different pH, salts and surfactants (both cationic and anionic) on partitioning has also been investigated.
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| 8. |
- Torto, Nelson, et al.
(författare)
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On-line quantitation of enzymatic mannan hydrolysates in small-volume bioreactors by microdialysis sampling and column liquid chromatography-integrated pulsed electrochemical detection
- 1996
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 725:1, s. 165-175
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative aspects of on-line microdialysis sampling are investigated with respect to sampling in small-volume bioreactors. Three modes of microdialysis sampling; continuous-flow microdialysis sampling (CFMS), stopped-flow microdialysis sampling with continuous stirring, and stopped-flow microdialysis sampling with stopped stirring were investigated as a possible means for studying bioprocesses. The hydrolytic properties of a well characterised endomannanase from Aspergillus niger were studied using 0.01% ivory nut mannan as substrate in a 5-ml reaction vessel. On-line sampling was achieved using a microdialysis probe fitted with an SPS 6005 membrane. Stopped-flow microdialysis sampling was found to give the least analyte depletion and thus used for quantitation of the enzymatic hydrolysates. However, CFMS can be used when analyte depletion is not significant (large-volume reactor). Hydrolysis of ivory nut mannan gave mainly mannobiose and mannotriose in almost equal amounts, which is consistent with an endo-wise hydrolysis. The concentrations of mannose and mannopentaose did not change significantly over the monitoring period, however, that of mannotetraose increased gradually up to 11 h where it starts to decrease.
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| 9. |
- Lim, Hwanmi, et al.
(författare)
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Benzo[a]pyrene-specific online high-performance liquid chromatography fractionation of air particulate extracts : a tool for evaluating biological interactions
- 2014
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Ingår i: Journal of Chromatography A. - Stockholm : Karolinska Institutet, Institute of Environmental Medicine. - 0021-9673 .- 1873-3778.
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Tidskriftsartikel (refereegranskat)abstract
- Benzo[a]pyrene (B[a]P) is a known human carcinogen and is commonly used as a surrogate for assessing the carcinogenic risk posed by complex mixtures of polycyclic aromatic hydrocarbons (PAHs) present in air particulate matter (PM). However, studies have shown that using B[a]P as a surrogate may underestimate the carcinogenic potential of PAH mixtures, as the risk assessment approach does not consider interaction effects. Thus, toxicological studies using B[a]P to assess its carcinogenic potential in environmentally derived complex mixtures, as opposed to single compound experiments, could improve risk assessment. The intention of the present study was to develop an online HPLC fractionation system for the selective removal of B[a]P from air PM extracts. Two serial pyrenylethyl (PYE) columns enabled selective separation of B[a]P from its isomers and other PAHs as well as a short fractionation cycle of 30min. One run consisted of three collection steps: the first fraction contained PAHs eluting earlier than B[a]P, the second contained B[a]P and the last contained later-eluting PAHs. The selectivity and recovery of the system was investigated using extracts of Stockholm air PM samples. The overall recovery for all PAHs was approximately 80%, and the system proved to be selective, as it removed 94% of B[a]P and less than 3% of benzo[b]fluoranthene from the complex PAH mixture. Exposing human cells to blanks generated by the fractionation system did not induce cytotoxicity or DNA damage signalling. In conclusion, the online HPLC system was selective for B[a]P fractionation whilst minimising run-to-run variation and allowing repeated fractionations for larger samples due to its relatively short run time.
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| 10. |
- Borchert, Axel, et al.
(författare)
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High-performance liquid affinity chromatography on silica-bound concanavalin A
- 1982
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Ingår i: Journal of chromatography. A. - 0021-9673. ; 244, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- Concanavalin A was covalently bound to porous silica (100-1000 Å) by three different coupling procedures. The performance of the preparations was evaluated from their ability to resolve a mixture of closely related sugars. The Concanavalin A-silica was used for efficient and rapid (5-20 min) analysis/purification of samples containing the glucoproteins peroxidase and glucose oxidase. Such columns could be used at least 60 times with retained performance.
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