| 1. |
- Ek, Patrik, et al.
(författare)
-
Electrospray Ionization from an Adjustable Gap between two Silicon Chips
- 2009
-
Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 44:2, s. 171-181
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a silicon chip - based electrospray emitter with a variable orifice size is presented. The device consists of two chips, with a thin beam elevating from the center of each of the chips. The chips are individually mounted to form an open gap of a narrow, uniform width between the top areas of the beams. The electrospray is generated at the endpoint of the gap, where the spray point is formed by the very sharp intersection between the crystal planes of the < 100 > silicon chips. Sample solution is applied to the rear end of the gap from a capillary via a liquid bridge, and capillary forces ensure a spontaneous imbibition of the gap. The sample solution is confined to the gap by means of a hydrophobic treatment of the surfaces surrounding the gap, as well as the geometrical boundaries formed by the edges of the gap walls. The gap width could be adjusted between 1 and 25 μm during electrospray experiments without suffering from any interruption of the electrospray process. Using a peptide sample solution, a shift toward higher charge states and increased signal-to-noise ratios was observed when the gap width was decreased. The limit of detection for the peptide insulin (chain B, oxidized) was approximately 4 nM. We also show a successful interfacing of the electrospray setup with capillary electrophoresis.
|
|
| 2. |
- Mikkonen, Saara, et al.
(författare)
-
Microfluidic Isoelectric Focusing of Amyloid Beta Peptides Followed by Micropillar-Matrix-Assisted Laser Desorption Ionization-Mass Spectrometry
- 2016
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 88:20, s. 10044-10051
-
Tidskriftsartikel (refereegranskat)abstract
- A novel method for preconcentration and purification of the Alzheimer’s disease related amyloid beta (Aβ) peptides by isoelectric focusing (IEF) in 75 nL microchannels combined with their analysis by micropillar-matrix-assisted laser desorption ionization-time-of-flight-mass spectrometry (MALDI-TOF-MS) is presented. A semiopen chip-based setup, consisting of open microchannels covered by a lid of a liquid fluorocarbon, was used. IEF was performed in a mixture of four small and chemically well-defined amphoteric carriers, glutamic acid, aspartyl-histidine (Asp-His), cycloserine (cSer), and arginine, which provided a stepwise pH gradient tailored for focusing of the C-terminal Aβ peptides with a pI of 5.3 in the boundary between cSer and Asp-His. Information about the focusing dynamics and location of the foci of Aβ peptides and other compounds was obtained using computer simulation and by performing MALDI-MS analysis directly from the open microchannel. With the established configuration, detection was performed by direct sampling of a nanoliter volume containing the focused Aβ peptides from the microchannel, followed by deposition of this volume onto a chip with micropillar MALDI targets. In addition to purification, IEF preconcentration provides at least a 10-fold increase of the MALDI-MS-signal. After immunoprecipitation and concentration of the eluate in the microchannel, IEF-micropillar-MALDI-MS is demonstrated to be a suitable platform for detection of Aβ peptides in human cerebrospinal fluid as well as in blood plasma.
|
|
| 3. |
- Dominguez, Marina A., et al.
(författare)
-
Capillary electrophoresis method for the simultaneous determination of carbohydrates and proline in honey samples
- 2016
-
Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 129, s. 1-4
-
Tidskriftsartikel (refereegranskat)abstract
- A capillary electrophoresis method with indirect UV detection for the simultaneous determination of three carbohydrates (fructose, glucose and sucrose) and the amino acid proline in honey samples was developed. This method included the use of a background electrolyte consisting of 10 mM sodium benzoate and 1.5 mM cetyltrimethylammonium bromide, pH 12.4. Under optimal capillary electrophoresis conditions, the separation of the investigated substances was achieved in less than 5 min and single dilution of each sample was employed. The detection limits for fructose, glucose and sucrose were 0.58 g L-1, 0.67 g L-1 and 0.12 g L-1 respectively, and 0.72 mg L-1 for proline. Precision measurements calculated in terms of %RSD in the range of 0.92 to 5.43%, were obtained. The proposed method was applied to honey samples from Argentina and Sweden and enables the determination of the three carbohydrates and the amino acid proline. The results show that the proposed method is simple, requires short analysis times, low consumption of reagents and sample, minimum waste and that there is no need to perform any sample pre-treatment. This method is a good alternative to carry out the quality control of honey samples. Finally, it is a promising methodology for achieving green chemistry goals.
|
|
| 4. |
- Hedberg, Yolanda, et al.
(författare)
-
Chromium-protein complexation studies by adsorptive cathodic stripping voltammetry and MALDI-TOF-MS
- 2012
-
Ingår i: Journal of Applied Electrochemistry. - : Springer Science and Business Media LLC. - 0021-891X .- 1572-8838. ; 42:5, s. 349-358
-
Tidskriftsartikel (refereegranskat)abstract
- A methodology using stripping voltammetry has been elaborated to enable sensitive and reliable protein-chromium complexation measurements. Disturbing effects caused by adsorption of proteins on the mercury electrode were addressed. At low concentrations of proteins (< 60-85 nM), chromium-protein complexation measurements were possible. Chromium(VI) complexation was quantitatively determined using differently sized, charged, and structured proteins: serum albumin (human and bovine), lysozyme, and mucin. Generated results showed a strong relation between complexation and protein size, concentration, and the number of amino acids per protein mass. Complexation increased nonlinearly with increasing protein concentrations. The nature of this complexation was based on weak interactions judged from combined results with MALDI-TOF-MS and adsorptive cathodic stripping voltammetry.
|
|
| 5. |
|
|
| 6. |
- Jacksén, Johan, et al.
(författare)
-
Capillary electrophoresis separation and matrix-assisted laser desorption/ionization mass spectrometry characterization of bovine serum albumin fluorescein isothiocyanate conjugates
- 2010
-
Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 878:15-16, s. 1125-1134
-
Tidskriftsartikel (refereegranskat)abstract
- A protocol using enzymatic digestion, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and capillary electrophoresis with laser induced fluorescence detection (CE-LIF) for the investigation of the binding of the fluorescent contact allergen fluorescein isothiocyanate (FITC) to the 66 kDa large protein bovine serum albumin (BSA), as a model system for protein-hapten binding in the skin, is presented. Mass spectra of BSA-FITC digestions, using trypsin and chymotrypsin, respectively, provided sequence coverage of 97%. To investigate the number of FITC-bound peptides using CE-LIF separation, three different buffer salts at four different pH levels were evaluated. The use of 20 mM sodium citrate pH 6.5 as well as 20 mM sodium phosphate pH 6.5 or pH 7.5 as background electrolyte revealed high numbers of peptides with at least one bound FITC. The effect of the electrolyte counter ion on MALDI-MS was investigated and was found to have effect on the MALDI spectra signal-to-noise (S/N) at 50 mM but not at 10 m M. Of the 60 theoretical FITC-binding sites in BSA this MALDI-MS protocol presents 30 defined. 28 possible and 2 non-binding sites for FITC. (C) 2010 Elsevier B.V. All rights reserved.
|
|
| 7. |
- Jacksén, Johan, et al.
(författare)
-
Capillary electrophoretic separation and fractionation of hydrophobic peptides onto a pre-structured matrix assisted laser desorption/ionization target for mass spectrometric analysis
- 2006
-
Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29:2, s. 288-295
-
Tidskriftsartikel (refereegranskat)abstract
- A CE separation of hydrophobic peptides followed by fractionation onto a prestructured MALDI target and off-line MS analysis was performed. An improved and partially automated manufacturing procedure of the previously described MALDI target is presented. This target is structurally coated with silicone and especially developed for hydrophobic peptides and proteins. Here, the target plate was designed specifically for the CE fraction collection. Different solvents were evaluated to meet the requirements of peptide solubility and compatibility to both the CE and MALDI methods and to the fractionation procedure. CE-MALDI-MS analysis of nine highly hydrophobic peptides from cyanogen bromide-digested bacteriorhodopsin is demonstrated.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Jacksén, Johan, et al.
(författare)
-
Evaluation of 2,6-dihydroxyacetophenone as matrix-assisted laser desorption/ionization matrix for analysis of hydrophobic proteins and peptides
- 2012
-
Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 425:1, s. 18-20
-
Tidskriftsartikel (refereegranskat)abstract
- Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is widely used for analysis of macromolecules like peptides and proteins. The analysis procedure is generally simple but must be adapted to the characteristics of the analytes. Therefore, specific matrices suitable for, e.g., hydrophobic proteins and peptides that are difficult to analyze would be preferable in order to optimize the outcome. In the present work, 2,6-dihydroxyacetophenone (DHAP) was shown to be beneficial in comparison to DHB for intact bacteriorhodopsin (BR) as well as for chemically digested BR.
|
|
