| 1. |
- Breimer, Michael, 1951, et al.
(author)
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Selected ion monitoring of glycospingolipid mixtures. Identification of several blood group type glycolipids in the small intestine of an individual rabbit.
- 1979
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In: Biomedical mass spectrometry. - : Wiley. - 0306-042X .- 1096-9888. ; 6:6, s. 231-41
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Journal article (peer-reviewed)abstract
- A novel application of selected ion monitoring was used for a mixture of non-acid glycosphingolipids of one rabbit small intestine. Earlier studies of permethylated and permethylated-reduced (LiAIH4) derivatives of model compounds have revealed a specificity and abundance of saccharide ions (terminal monosaccharide(s), disaccharide, trisaccharide, etc., and all sugars plus fatty acid) and of ceramide fragments that permit a conclusive detection of separate glycolipid species in a mixture. The sample (50-200 micrograms) was evaporated slowly (1-5 degrees C min-1 from 150-350 degrees C) from the direct inlet probe of an MS 902 mass spectrometer (electron ionization). Mass spectra with fragments up to about m/z 200 were collected on-line by a computer system. A successive partial separation was obtained for glycolipids with from one up to seven sugars. The structures of eight different compounds were identified. They all had 16:0, 22:0 and 24:0 2-hydroxy fatty acids and 18:0 trihydroxy base (phytosphingosine) as major ceramide components. The dominating complex glycolipid was a hexaglycosylceramide with a blood group B type of sequence. A blood group A type sequence was found in a second hexaglycosylceramide. In support of this, the native mixture showed blood group A and B activity. An intense peak, m/z 182, collected from methylated derivatives were evidence for a dominating type 2 carbohydrate chain of the core tetrasaccharide.
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| 2. |
- Löfstedt, Christer, et al.
(author)
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Analysis of moth pheromone acetates by selected ion monitoring using electron impact and chemical ionization mass spectrometry
- 1984
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In: Biological Mass Spectrometry. - : Wiley. - 0306-042X .- 1096-9888. ; 11:3, s. 106-113
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Journal article (peer-reviewed)abstract
- Mass spectrometric determination of moth pheromone components by means of selected ion monitoring with electron impact and chemical ionization has been evaluated. For the analysis of acetates, chemical ionization with ammonia as reactant gas proved advantageous with respect to sensitivity and selectivity. A quantitative assay for determination of pheromone samples from individual turnip moth females (Agrotis segetum, Noctuidae), using internal standards, deuterated at the acyl group, was developed. The assay showed correct linearity in the investigated region (20–2000 pg). Signal to noise ratios for 100 pg of acetates using chemical ionization (ammonia as reactant gas) were in the range 10–50 depending on the degree of unsaturation. Conservative limits of detection (background signal + three times the standard deviation) and quantification (background signal + 10 times the standard deviation) were approximately 70 and 240 pg, respectively. A significant decrease in gland titre of (Z)‐5‐decenyl acetate and (Z)‐7‐dodecenyl acetate after mating was established.
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| 3. |
- Tunlid, Anders, et al.
(author)
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Diastereoisomeric determination of R‐alanine in bacteria using capillary gas chromatography and positive/negative ion mass spectrometry
- 1984
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In: Biological Mass Spectrometry. - : Wiley. - 0306-042X .- 1096-9888. ; 11:8, s. 428-434
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Journal article (peer-reviewed)abstract
- The possibilities of using combined capillary gas chromatography mass spectrometry for highly sensitive and selective determinations of enantiomeric alanines of bacterial origin have been evaluated. The alanines were separated as their diastereoisomeric N‐heptafluorobutyryl‐2‐butyl ester derivatives on a 25 m fused silica capillary column coated with SE‐54 as stationary phase. The mass spectra of the derivative obtained by chemical ionization using methane or ammonia (positive ions) and methane or Isobutane (negative ions) as reagent gases have been recorded. The highest sensitivity of detection was achieved by selected ion monitoring in the negative ion mode (detection limit about 0.8 pg). The method was tested by measuring the R‐alanine content in (a) Escherichia coli cultures and (b) natural bacterial communities associated with plant roots. In (a) the recorded detection limit implied possibilities to detect R‐alanine corresponding to 103−104 E. coli cells. The precision for quantifying R‐alanine in the cultures was 14% (coefficient of variation). (b) demonstrated an application where the R/(R + S) ratio of alanine is low. It was shown that accurate determinations of this ratio in the picogram range could be effected down to 0.4%.
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| 4. |
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| 5. |
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| 6. |
- Bankefors, Johan, et al.
(author)
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Electrospray ionization ion-trap multiple-stage mass spectrometry of Quillaja saponins
- 2011
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In: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 46, s. 658-665
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Journal article (peer-reviewed)abstract
- Fifteen identified C-18 fatty acyl-containing saponin structures from Quillaja saponaria Molina have been investigated by electrospray ionization ion-trap multiple-stage mass spectrometry (ESI-IT-MS(n)) in positive ion mode. Their MS(1)-MS(3) spectra were analyzed and ions corresponding to useful fragments, important for the structural identification of Quillaja saponins, were recognized. A few key fragments could describe the structural variations in the C-3 and the C-28 oligosaccharides of the Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from the MS(1)-MS(3) spectra of these saponins, together with key fragments from these saponins and 13 previously investigated saponins, was constructed for the identification of structural elements in Quillaja saponins. Peak intensity ratios in MS(3) spectra were found to be correlated to structural features of the investigated saponins and is therefore of value for the identification of regioisomers. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 7. |
- Bazoti, Fotini N, et al.
(author)
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Study of the non-covalent interaction between amyloid-beta-peptide and melatonin using electrospray ionization mass spectrometry
- 2005
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In: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 40:2, s. 182-192:40, s. 182-192
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Journal article (peer-reviewed)abstract
- Oxidative stress and unregulated immune response are believed to play a key role in the processes inherent to Alzheimer's disease (AD). The fact that free radicals can result in neurodegeneration suggests that actions against reactive oxygen species may be beneficial in treating and preventing AD. In the light of the suggested link between oxidative stress and AD, it is proposed that antioxidants and, even more, endogenous antioxidants may offer a therapeutic regime for protection against the risk of this disease. For this reason, the formation of non-covalent complexes between amyloid-beta-peptide (A beta) or its oxidized forms and melatonin was studied by quadrupole and Fourier transform ion cyclotron resonance electrospray ionization mass spectrometry. The stability of the non-covalent complex was examined under several experimental conditions, such as orifice voltage, pH, presence of organic modifier, concentration and time. Two different digestion protocols combined with mass spectrometric analysis of the resulting peptide fragments were employed in order to locate the binding site of melatonin in A beta.
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| 8. |
- Benkestock, Kurt, et al.
(author)
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Influence of droplet size, capillary-cone distance and selected instrumental parameters for the analysis of noncovalent protein-ligand complexes by nano-electrospray ionization mass spectrometry
- 2004
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In: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 39:9, s. 1059-1067
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Journal article (peer-reviewed)abstract
- It has been suggested in the literature that nano-electrospray ionization (nano-ESI) mass spectrometry better reflects the equilibrium between complex and free protein in solution than pneumatically assisted electrospray ionization (ESI) in noncovalent interaction studies. However, no systematic studies of the effects of ionization conditions have been performed to support this statement. In the present work, different instrumental and sample-derived parameters affecting the stability of noncovalent complexes during analysis by nano-ESI were investigated. In general, increased values of parameters such as drying gas flow-rate, ion-source temperature, capillary tip voltage and buffer concentration lead to a dissociation of ribonuclease A (RNAse)-cytidine 2'-monophosphate (CMP) and cytidine 5'-triphosphate (CTP) complexes. The size of the electrosprayed droplets was shown to be an important issue. Increasing the capillary to cone distance yielded an increased complex to free protein ratio when a hydrophilic ligand was present and the reverse effect was obtained with a hydrophobic ligand. Important in this regard is the degree of sampling of ions originating from late-generation residue droplets, that is, ions present in the droplet bulk. Sampling of these ions increases with longer capillary-cone distance (flight time). Furthermore, when the sample flow-rate was increased by increasing the capillary internal tip i.d. from 4 to 30 mum, a decreased complex to free protein ratio for the RNAse-CTP system was observed. This behavior was consistent with the change in surface to volume ratio for flow-rates between 2 and 100 nl min(-1). Finally, polarity switching between positive and negative ion modes gave a higher complex to free protein ratio when the ligand and the protein had the same polarity.
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| 9. |
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| 10. |
- Boija, Susanne, et al.
(author)
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Determination of conditional stability constants for some divalent transition metal ion-EDTA complexes by electrospray ionization mass spectrometry
- 2014
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In: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 49:7, s. 550-556
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Journal article (peer-reviewed)abstract
- Conditional stability constants of coordination complexes comprising divalent transition metals, Cu2+, Ni2+, Zn2+, Co2+, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co2+ and Zn2+ competed for EDTA at pH 5. When Cu2+ and Ni2+ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.
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