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Publications (10 of 48) Show all publications
Romson, J., Jacksen, J. & Emmer, Å. (2019). An automated system for CE-MALDI and on-target digestion under a fluorocarbon lid applied on spermatophore proteins from Pieris napi. Journal of chromatography. B, 1104, 228-233
Open this publication in new window or tab >>An automated system for CE-MALDI and on-target digestion under a fluorocarbon lid applied on spermatophore proteins from Pieris napi
2019 (English)In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1104, p. 228-233Article in journal (Refereed) Published
Abstract [en]

A method for off-line CE-MALDI-TOF-MS and MS2, and on-target digestion under a fluorocarbon lid was developed and applied for the analysis of proteins in the spermatophore of the butterfly Pieris napi. Fractionation revealed many peptides otherwise not detected or resolved. Automated fractionation was performed with an in-lab developed robotic system, and automated on-target tryptic digestion under a fluorocarbon lid was demonstrated with the same system. Fractionation onto a pre-structured MALDI-concentration plate facilitated aligned deposition of trypsin and MALDI-matrix with the deposited sample, also under the fluorocarbon lid. Some indications of indigenous proteolysis of spermatophore proteins were seen, and searching MS2 spectra suggested three tentative sequence homologies to P. rapae. The study demonstrates the functionality of the lab-made robot. Detailed manufacturing instructions and code are provided. The feasibility of automated on-target digestion under a fluorocarbon lid, and the usefulness of a structured concentration plate in CE-MALDI fractionation was shown. Further, it constitutes a preliminary study of P. napi spermatophore proteins.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
CE-MALDI-MS2, On-target digestion, Automation, Robot, Pieris napi, Spermatophore
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-244140 (URN)10.1016/j.jchromb.2018.11.021 (DOI)000456890000029 ()30530115 (PubMedID)2-s2.0-85057615872 (Scopus ID)
Note

QC 20190218

Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2019-02-18Bibliographically approved
Josefsson, L., Larsson, M. K., Bjällmark, A. & Emmer, Å. (2016). Analysis of polyvinyl alcohol microbubbles in human blood plasma using capillary electrophoresis. Journal of Separation Science, 39(8), 1551-1558
Open this publication in new window or tab >>Analysis of polyvinyl alcohol microbubbles in human blood plasma using capillary electrophoresis
2016 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 39, no 8, p. 1551-1558Article in journal (Refereed) Published
Abstract [en]

Recently, a new type of ultrasound contrast agent that consists of air-filled microbubbles stabilized with a shell of polyvinyl alcohol was developed. When superparamagnetic nanoparticles of iron oxide are incorporated in the polymer shell, a multimodal contrast agent can be obtained. The biodistribution and elimination pathways of the polyvinyl alcohol microbubbles are essential to investigate, which is limited with today's techniques. The aim of the present study was, therefore, to develop a method for qualitative and quantitative analysis of microbubbles in biological samples using capillary electrophoresis with ultraviolet detection. The analysis parameters were optimized to a wavelength at 260 nm and pH of the background electrolyte ranging between 11.9 and 12. Studies with high-intensity ultrasonication degraded microbubbles in water showed that degraded products and intact microbubbles could be distinguished, thus it was possible to quantify the intact microbubbles solely. Analysis of human blood plasma spiked with either plain microbubbles or microbubbles with nanoparticles demonstrated that it is possible to separate them from biological components like proteins in these kinds of samples.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2016
Keywords
Capillary electrophoresis, Contrast agents, Human blood plasma, Polyvinyl alcohol microbubbles
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:kth:diva-187204 (URN)10.1002/jssc.201501342 (DOI)000374773000018 ()2-s2.0-84963701455 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 245572
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-18 Last updated: 2017-11-30Bibliographically approved
Springer, V., Jacksén, J., Ek, P., Lista, A. G. & Emmer, Å. (2015). Capillary Electrophoretic Determination of Fluoroquinolones in Bovine Milk Followed by Off-Line MALDI-TOF-MS Analysis. Chromatographia, 78(3-4), 285-290
Open this publication in new window or tab >>Capillary Electrophoretic Determination of Fluoroquinolones in Bovine Milk Followed by Off-Line MALDI-TOF-MS Analysis
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2015 (English)In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 78, no 3-4, p. 285-290Article in journal (Refereed) Published
Abstract [en]

A novel appro ach for the determination of ciprofloxacin, norfloxacin and ofloxacin by capillary electrophoresis and off-line capillary electrophoresis-matrix-assisted laser desorption/ionization-time of flight-mass spectrometry coupling for the confirmation of analyte identities is presented. A polymer capillary coating was proposed with the aim to minimize suppression of the MS signal caused by the CE solution components. The fluoroquinolones were successfully separated and determined by CE-UV followed by fractionation onto a MALDI plate and off-line MS characterization. Full-cream and low-fat milk samples were used to illustrate that the proposed method represents an efficient alternative for fluoroquinolone antibiotics determination in milk.

Keywords
Capillary electrophoresis, Matrix-assisted laser desorption/ionization mass spectrometry, Fluoroquinolones, Off-line integration
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-161110 (URN)10.1007/s10337-014-2823-5 (DOI)000348976900016 ()2-s2.0-84925487438 (Scopus ID)
Note

QC 20150323

Available from: 2015-03-23 Created: 2015-03-09 Last updated: 2017-12-04Bibliographically approved
Mikkonen, S., Thormann, W. & Emmer, Å. (2015). Computer simulations of sample preconcentration in carrier-free systems and isoelectric focusing in microchannels using simple ampholytes. Electrophoresis, 36(19), 2386-2395
Open this publication in new window or tab >>Computer simulations of sample preconcentration in carrier-free systems and isoelectric focusing in microchannels using simple ampholytes
2015 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 36, no 19, p. 2386-2395Article in journal (Refereed) Published
Abstract [en]

In this work, electrophoretic preconcentration of protein and peptide samples in microchannels was studied theoretically using the 1D dynamic simulator GENTRANS, and experimentally combined with MS. In all configurations studied, the sample was uniformly distributed throughout the channel before power application, and driving electrodes were used as microchannel ends. In the first part, previously obtained experimental results from carrier-free systems are compared to simulation results, and the effects of atmospheric carbon dioxide and impurities in the sample solution are examined. Simulation provided insight into the dynamics of the transport of all components under the applied electric field and revealed the formation of a pure water zone in the channel center. In the second part, the use of an IEF procedure with simple well defined amphoteric carrier components, i.e. amino acids, for concentration and fractionation of peptides was investigated. By performing simulations a qualitative description of the analyte behavior in this system was obtained. Neurotensin and [Glu1]-Fibrinopeptide B were separated by IEF in microchannels featuring a liquid lid for simple sample handling and placement of the driving electrodes. Component distributions in the channel were detected using MALDI- and nano-ESI-MS and data were in agreement with those obtained by simulation. Dynamic simulations are demonstrated to represent an effective tool to investigate the electrophoretic behavior of all components in the microchannel.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2015
Keywords
Isoelectric focusing, Mass spectrometry, Microchip, Preconcentration, Simulation
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-175914 (URN)10.1002/elps.201500120 (DOI)000362187700003 ()26036978 (PubMedID)2-s2.0-84957847418 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20151104

Available from: 2015-11-04 Created: 2015-10-26 Last updated: 2017-12-01Bibliographically approved
Rokhas, M. K., Mikkonen, S., Beyer, J., Jacksén, J. & Emmer, Å. (2014). CE analysis of single wood cells performing hydrolysis and preconcentration in open microchannels. Electrophoresis, 35(2-3), 450-457
Open this publication in new window or tab >>CE analysis of single wood cells performing hydrolysis and preconcentration in open microchannels
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2014 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 35, no 2-3, p. 450-457Article in journal (Refereed) Published
Abstract [en]

In the present work, monosaccharides from pulp samples and single wood fibers were analyzed with CE, using indirect detection due to the lack of chromophores on the monosaccharides. The hydrolysis degradation of cellulose and hemicellulose into monosaccharides was performed using TFA, either in bulk scale or in microscale. In the microscale, one single wood fiber was hydrolyzed in an open microchannel manufactured on a silicon microchip with the dimensions 50 μm × 50 μm (length 1 or 3 cm). The low monosaccharide amounts derived from a single fiber implied that a preconcentration step was necessary to increase the detectability. Thus, an electromigration preconcentration of the hydrolyzed samples was performed within the microchannel, which resulted in a significantly enhanced signal intensity of the monosaccharides. In addition to the experimental study, computer simulations were performed regarding the preconcentration step of monosaccharides. The results from these simulations correlated well with the experimental results.

Keywords
Capillary electrophoresis, Open microchannels, Preconcentration, Wood cells
National Category
Other Chemistry Topics Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-143085 (URN)10.1002/elps.201300408 (DOI)000331899400028 ()2-s2.0-84892478458 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4095
Note

QC 20140317

Available from: 2014-03-17 Created: 2014-03-17 Last updated: 2017-12-05Bibliographically approved
Springer, V., Jacksén, J., Ek, P., Lista, A. G. & Emmer, Å. (2014). Determination of fluoroquinolones in bovine milk samples using a pipette-tip SPE step based on multiwalled carbon nanotubes prior to CE separation. Journal of Separation Science, 37(1-2), 158-164
Open this publication in new window or tab >>Determination of fluoroquinolones in bovine milk samples using a pipette-tip SPE step based on multiwalled carbon nanotubes prior to CE separation
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2014 (English)In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 37, no 1-2, p. 158-164Article in journal (Refereed) Published
Abstract [en]

A simple CE-UV method was developed for the simultaneous determination of ciprofloxacin, norfloxacin, and ofloxacin in milk samples. The optimum separation was obtained using a 20 mM ammonium dihydrogenphosphate solution with 2 mM cetyltrimethylammonium bromide at pH 3.0 as the BGE. Satisfactory resolution for structurally very similar analytes, like norfloxacin and ciprofloxacin, was achieved without including any organic solvent. Milk samples were prepared using a simple/extraction procedure based on acidic protein precipitation followed by an SPE step using only 5 mg of multiwalled carbon nanotubes as the sorbent material. The LODs for the three compounds were between 7.5 and 11.6 g/L and the RSDs for the peak areas were between 2.6 and 4.9%. The complete method was applied to spiked real milk samples with satisfactory recoveries for all analytes (84-106%).

Keywords
CE, Fluoroquinolones, Multiwalled carbon nanotubes, SPE
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-140664 (URN)10.1002/jssc.201300980 (DOI)000329478100023 ()
Note

QC 20140131

Available from: 2014-01-31 Created: 2014-01-30 Last updated: 2017-12-06Bibliographically approved
Mikkonen, S., Jacksén, J. & Emmer, Å. (2014). Mass spectrometric analysis of nanoscale sample volumes extracted from open microchannels after sample preconcentration applied on amyloid beta peptides. Analytical and Bioanalytical Chemistry, 406(14), 3521-3524
Open this publication in new window or tab >>Mass spectrometric analysis of nanoscale sample volumes extracted from open microchannels after sample preconcentration applied on amyloid beta peptides
2014 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 406, no 14, p. 3521-3524Article in journal (Refereed) Published
Abstract [en]

A new instrumental concept for extraction of nanovolumes from open microchannels (dimensions 150 mu m x 50 mu m, length 10 mm) manufactured on silicon microchips has been used in combination with a previously developed method for preconcentrating proteins and peptides in the open channels through electromigration. The extracted nanovolumes were further analyzed using nanoelectrospray ionization (nESI) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) directly or with subsequent enzymatic protein digestion in a nanodroplet prior to the MS analysis. Preconcentration of the samples resulted in a 15-fold sensitivity increase in nESI for a neurotensin solution, and using MALDI-MS, amyloid beta (A beta) peptides could be detected in concentrations down to 1 nM. The method was also successfully applied for detection of cell culture A beta.

Keywords
Mass spectrometry, Microchannel, Preconcentration, Amyloid beta, MALDI, Nano-ESI
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-147047 (URN)10.1007/s00216-014-7781-0 (DOI)000336261800030 ()2-s2.0-84901603229 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4095
Note

QC 20140624

Available from: 2014-06-24 Created: 2014-06-23 Last updated: 2017-12-05Bibliographically approved
Hedberg, Y., Lundin, M., Jacksén, J., Emmer, Å., Blomberg, E. & Wallinder, I. O. (2012). Chromium-protein complexation studies by adsorptive cathodic stripping voltammetry and MALDI-TOF-MS. Journal of Applied Electrochemistry, 42(5), 349-358
Open this publication in new window or tab >>Chromium-protein complexation studies by adsorptive cathodic stripping voltammetry and MALDI-TOF-MS
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2012 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 42, no 5, p. 349-358Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Chromium, Complexation, Lysozyme, Serum albumin, Mucin, Stripping voltammetry
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-93903 (URN)10.1007/s10800-012-0404-6 (DOI)000302410900009 ()
Funder
Swedish Research Council
Note
QC 20120504Available from: 2012-05-04 Created: 2012-05-03 Last updated: 2017-12-07Bibliographically approved
Jacksén, J. & Emmer, Å. (2012). Evaluation of 2,6-dihydroxyacetophenone as matrix-assisted laser desorption/ionization matrix for analysis of hydrophobic proteins and peptides. Analytical Biochemistry, 425(1), 18-20
Open this publication in new window or tab >>Evaluation of 2,6-dihydroxyacetophenone as matrix-assisted laser desorption/ionization matrix for analysis of hydrophobic proteins and peptides
2012 (English)In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 425, no 1, p. 18-20Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
DHAP, Hydrophobic protein/peptides, MALDI-MS, Matrix
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-96183 (URN)10.1016/j.ab.2012.02.039 (DOI)000303950100004 ()2-s2.0-84859323545 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4095
Note
QC 20120531Available from: 2012-05-31 Created: 2012-05-31 Last updated: 2017-12-07Bibliographically approved
Mikkonen, S., Rokhas, M. K., Jacksén, J. & Emmer, Å. (2012). Sample preconcentration in open microchannels combined with MALDI-MS. Electrophoresis, 33(22), 3343-3350
Open this publication in new window or tab >>Sample preconcentration in open microchannels combined with MALDI-MS
2012 (English)In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 33, no 22, p. 3343-3350Article in journal (Refereed) Published
Abstract [en]

In this work, a method for preconcentrating samples in 1 cm long, 50-150 μm wide open microchannels is presented. Platinum electrodes were positioned at the channel ends, voltage was applied, and charged analyte was preconcentrated at the oppositely charged side during continuous supply of sample. The preconcentration was initially studied in a closed system, where an influence on the analyte position from a pH gradient, generated by water electrolysis, was observed. In the open channel, the analyte distribution after preconcentration was evaluated using MALDI-MS with the channel as MALDI target. MALDI matrix was applied with an airbrush or by electrospray matrix deposition and by using the latter technique higher degrees of crystallization in the channels were obtained. After preconcentrating a 1 nM cytochrome c solution for 5 min, corresponding to a supplied amount of 1.25 fmol, a signal on the cathodic channel end could be detected. When a solution of cytochrome c trypsin digest was supplied, the peptides were preconcentrated at different positions along the channel depending on their charge.

Keywords
Electrospray deposition, MALDI-MS, Preconcentration, Silicon microchip
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-108041 (URN)10.1002/elps.201200129 (DOI)000311303100013 ()2-s2.0-84869782576 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20121220

Available from: 2012-12-20 Created: 2012-12-19 Last updated: 2017-12-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3444-9987

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