| 1. |
- Karlsson, Maria, et al.
(författare)
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Lignin Structure and Reactivity in the Organosolv Process Studied by NMR Spectroscopy, Mass Spectrometry, and Density Functional Theory
- 2023
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 24:5, s. 2314-2326
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Tidskriftsartikel (refereegranskat)abstract
- There is need for well-defined lignin macromolecules for research related to their use in biomaterial and biochemical applications. Lignin biorefining efforts are therefore under investigation to meet these needs. The detailed knowledge of the molecular structure of the native lignin and of the biorefinery lignins is essential for understanding the extraction mechanisms as well as chemical properties of the molecules. The objective of this work was to study the reactivity of lignin during a cyclic organosolv extraction process adopting physical protection strategies. As references, synthetic lignins obtained by mimicking the chemistry of lignin polymerization were used. State-of-the-art nuclear magnetic resonance (NMR) analysis, a powerful tool for the elucidation of lignin inter-unit linkages and functionalities, is complemented with matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF MS), to gain insights into linkage sequences and structural populations. The study unraveled interesting fundamental aspects on lignin polymerization processes, such as identifications of molecular populations with high degrees of structural homogeneity and the emergence of branching points in lignin structure. Furthermore, a previously proposed intramolecular condensation reaction is substantiated and new insights into the selectivity of this reaction are introduced and supported by density functional theory (DFT) calculations, where the important role of intramolecular π-π stacking is emphasized. The combined NMR and MALDI-TOF MS analytical approach, together with computational modeling, is important for deeper fundamental lignin studies and will be further exploited.
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| 2. |
- Romson, Joakim, et al.
(författare)
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An automated system for CE-MALDI and on-target digestion under a fluorocarbon lid applied on spermatophore proteins from Pieris napi
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Ingår i: Journal of chromatography. B. - 1570-0232 .- 1873-376X.
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Romson, Joakim, et al.
(författare)
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An automated system for CE-MALDI and on-target digestion under a fluorocarbon lid applied on spermatophore proteins from Pieris napi
- 2019
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Ingår i: Journal of chromatography. B. - : ELSEVIER SCIENCE BV. - 1570-0232 .- 1873-376X. ; 1104, s. 228-233
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Romson, Joakim, et al.
(författare)
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Chemical mass shifts of cluster ions and adduct ions in quadrupolar ion traps revisited and extended
- 2023
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 37:3
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Tidskriftsartikel (refereegranskat)abstract
- RationaleChemical mass shifts in quadrupolar ion traps have been studied previously but only for a limited number of analytes and mass ranges. Here, mass shifts of cluster ions, commonly used as calibrants, and other analytes are qualitatively evaluated on the Bruker amaZon spherical ion trap (QIT) and the Finnigan LXQ linear ion trap (LIT). To extend the mass range from previous experiments m/z up to 4000 are investigated. MethodsChemical mass shifts of CsI, Y(HCOO)(3), and NaCF3COO cluster ions, CF3COO-, Na+, and Cs+ adduct ions, protonated commercial calibration solutions and peptides, and deprotonated peptides were investigated on the Bruker amaZon speed QIT and some of these were also investigated on the Finnigan LXQ LIT. ResultsOn both instruments, peak distortions and mass shifts toward lower m/z became apparent as m/z approached 1000. To some extent, the issues were more severe at slower scans. Peak distortions included loss of resolution, tailing, or fronting and were different between the amaZon QIT and the LXQ LIT. The noncluster and nonadduct ions analyzed showed no obvious mass shifts or peak distortions under the same analysis conditions. ConclusionsAs expected, the ion traps investigated here showed mass shift and peak distortion issues, and such issues persisted at m/z up to 4000 on both instruments. Peak distortions were different between the amaZon QIT and the LXQ LIT, and were not always visible despite mass shifts. Both mass shifts and peak distortions make cluster ions and some adduct ions unsuitable for ion trap calibration.
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| 5. |
- Romson, Joakim, et al.
(författare)
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Chemical mass shifts of cluster ions and adduct ions in spherical and linear ion traps
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Rationale Chemical mass shifts in spherical ion traps (quadrupole ion traps, QIT) have been studiedpreviously but the full scope of these shifts is not certain, and linear ion traps (LIT) have not beenextensively evaluated. Here, mass shifts of cluster ions, commonly used as calibrants, and otheranalytes, are evaluated on a QIT and a LIT. As mass shifts at higher m/z have not been studiedpreviously, and as few analytes other than clusters reach m/z over 3000, dendrimers ranging m/z 2000- 4000 were investigated.Methods Chemical mass shifts of CsI, Y(HCOO)3, and NaCF3COO cluster ions, and CF3COO--, Na+-, andCs+-adduct ions, protonated commercial calibration solutions and peptides, and deprotonatedpeptides were investigated on a Bruker amaZon speed QIT, and some of them on a Finnigan LXQ LIT.Results On both instruments, cluster ions and some adduct ions showed peak distortion, mass shiftstoward lower m/z that tended to increase at higher m/z, and, to limited extent, larger at slower scans.Unexpectedly, the slowest scans on both instruments improved peak shapes and mass shifts. Peakdistortions included loss of resolution, tailing, or fronting, and were different for the LIT and QIT. Noncluster and non-adduct ions showed no mass shifts or peak distortions under the same analysisconditions. Analysis without He-buffer gas showed decreased relative mass shifts and decreased peakdistortion for peaks showing shifts and distortion under normal conditions.Conclusions Mass shifts in both the QIT and the LIT corresponded reasonably well to collision induceddissociation during ion ejection. Peak distortions were different for the QIT and the LIT, and not alwaysvisible despite mass shifts. Both mass shifts and peak distortion make cluster ions and some adductions unsuitable for ion trap calibration. Na+-adducts of high-mass dendrimers showed small signs ofmass shifts and further studies on high-mass dendrimers is suggested.
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| 6. |
- Romson, Joakim, et al.
(författare)
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ESI-MSn Analysis of Recombinant Human Osteopontin
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The low-abundance protein osteopontin is implicated in several serious diseases, where its concentration andglycosylation patterns might be analyzed for its use as a biomarker. The glycosylation has previously been studied andcharacterized mainly on digested protein. Allowing analysis of glycosylation using the intact protein would reduce theworkload and analysis time, as well as introducing less potential sources of error and bias. Here, the detection of intactosteopontin by ESI-MS is presented. By using a matrix with a high proportion of isopropanol, osteopontin could be detectedand fragmented in tandem MS at 10 µg/mL by direct infusion. A lower osteopontin mass was also present in the sample. Theresults open the possibilities of further analysis of osteopontin by tandem MS and suggests a reporter ion.
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| 7. |
- Romson, Joakim, et al.
(författare)
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Mass Calibration Options for Accurate Electrospray Ionization Mass Spectrometry
- 2021
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 467
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Tidskriftsartikel (refereegranskat)abstract
- Calibration is vital for accurate m/z measurements. This review informs on calibration and possible calibrants for ESI-MS, highlighting analytical considerations important for high accuracy and precision. External calibration is often easier to perform, but the best accuracies are obtained with internal calibration, especially with calibrants close to and bracketing the analyte(s). Clusters of CsI allow the highest m/z calibration points, but other clusters give more closely spaced signals (clusters are unsuitable for ion trap calibration). Polymers such as PEG and PPG give closely spaced signals over a limited mass range, but suffer from memory effects. Commercial calibration solutions are easy to use and good for general calibration, but may be expensive and hard to modify. Proteins, peptides, small organic molecules, and some other calibrants offer high customization and may be preferred for more specific analyses, often for analysis of similar molecules. Because both accuracy and precision need to be known before measuring unknowns, the instrument should be evaluated. To avoid interferences, such as overlapping signals, it is important to keep the instrument and solutions free from contamination. Overlapping signals that cause shifts can, but may not, result in peak asymmetry, and smoothing can further obscure partially resolved interferences. Although increased resolution may resolve interfering signals, increased resolution can lead to lower sensitivity, potentially leading to loss of precision and accuracy due to poor ion statistics. Low intensity can to some extent be compensated by averaging more spectra. Trapping instruments suffer from space charge effects, so for the best results the number of ions needs to be limited but still high enough for sufficient ion statistics, and matching between calibration and analysis.
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| 8. |
- Romson, Joakim, 1991-
(författare)
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Methods for protein analysis by capillary electrophoresis and mass spectrometry
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protein analysis is important to understanding biological systems, but sample diversity necessitates a multitude of analysis techniques and methods. Challenges that are addressed include analysis of low abundance samples, fractionation to reduce sample complexity, and automation to reduce time and cost.Matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) is an important technique for protein characterization. In Paper I, the sensitivity of MALDI-MS was enhanced through the fabrication of a hydrophobic coating for the MALDI target plate, yielding analyte concentration. The plate outperformed a commercial concentration plate.Capillary electrophoresis (CE) separation offers low sample consumption and high efficiency, and in Paper II, offline CE-MALDI-MS fractionation was employed. A robot system for automation was constructed and used in analysis of spermatophore proteins from the butterfly Pieris napi. The robot was also used in automated on-target trypsin digestion under a lid of liquid fluorocarbons, a simpler and cheaper alternative to controlled humidity chambers. An indication of indigenous proteolysis of the sample was seen.Electrospray ionization (ESI) is the other technique for protein analysis in MS. In Paper III, the biomarker protein osteopontin (OPN) was analyzed by ESI-MS in order to find suitable conditions for its detection. A preliminary optimization of solvents and ionization conditions was done, and tandem MS (MSn) performed to increase the reliability of identification.
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| 9. |
- Romson, Joakim, et al.
(författare)
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Simple and environmentally friendly fabrication of superhydrophobic alkyl ketene dimer coated MALDI concentration plates
- 2017
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Ingår i: Journal of the American Society for Mass Spectrometry. - : Springer. - 1044-0305 .- 1879-1123. ; 28:8, s. 1733-1736
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Tidskriftsartikel (refereegranskat)abstract
- Here we present a method to manufacture peptide-concentrating MALDI-plates with alkyl ketene dimer (AKD) as a new superhydrophobic coating. The fabrication of the hydrophobic plates included application of AKD by airbrush, and negative contact printing to generate the concentration sites. Deposited sample droplets were contained within the prestructured sites, and self-adjusted onto the site if slightly misplaced. No AKD contamination was observed, and the plates could easily be cleaned and regenerated. The S/N values for four model peptides was about twice as high compared with a standard steel plate and a commercial concentration plate.
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| 10. |
- Romson, Joakim, et al.
(författare)
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SpheriCal(R)-ESI : A dendrimer-based nine-point calibration solution ranging from m/z 273 to 1716 for electrospray ionization mass spectrometry peptide analysis
- 2021
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 35:5
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Tidskriftsartikel (refereegranskat)abstract
- Rationale A calibration solution for mass spectrometry needs to cover the range of interest with intense and sufficiently narrowly spaced peaks. Limited options fulfilling this may lead to compromises between performance and ease of use. SpheriCal(R)-ESI was designed to combine high calibration performance for electrospray ionization (ESI) mass spectrometric analysis of peptides in positive mode with quick and easy use. Methods The developed calibration solution was tested using three mass spectrometers: two ion traps and one tandem quadrupole. The m/z errors of SpheriCal(R)-ESI itself and of a tryptic digest of cytochrome C were measured after calibration. The results were compared with those achieved with ESI Tuning Mix. The memory effects of the dendrimers, and contamination from Na+ in the calibration solution, were evaluated. Results SpheriCal(R)-ESI showed good shelf life as powder and was quickly reconstituted for use. Achieving intense and stable signals was straightforward. The accuracies and precisions were as expected for the instruments. SpheriCal(R)-ESI was more precise and at least as accurate as ESI Tuning Mix. The memory effects and Na+ contamination were found to be negligible in typical peptide solvents. In addition, the dendrimers showed predictable dissociations with product ions common to collision-induced dissociation in both ion trap and tandem quadrupole mass spectrometers. Conclusions SpheriCal(R)-ESI provided easily accessible calibration by showing intense signals at low infusion rates and at source settings equal or similar to those used in peptide analysis. Nine calibration points in the range of interest gave precise and accurate results. Memory effects and contamination were negligible even without rinsing.
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| 11. |
- Romson, Joakim
(författare)
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Tools for applied soft ionization mass spectrometry
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mass spectrometry (MS) is an important analytical tool. Its most importantadvantages are sensitivity, resolution, and accurate and precise m/zmeasurements. To get the best results from an instrument, the user musthave knowledge of its limitation and requirements.The sensitivity of matrix assisted laser desorption/ionization (MALDI)-MSis dependent on the surface concentration of the sample. In Paper I, ahighly hydrophobic surface coating was developed and applied to MALDItarget plates. This allowed applied sample droplets to dry down ontosmaller areas. Compared to untreated and commercial concentrationplates, the surface treated plates gave on average twice the signal to noisefor peptide analysis.Signal suppression and signal overlap in MS can obscure analyte signals.In Paper II, an automated system for coupling capillary electrophoresis toMALDI-MS was developed. Separation of butterfly spermatophoreproteins into 32 fractions revealed some otherwise not detected oroverlapping MS signals.Calibration is vital for accurate MS measurements. In Paper III, adendrimer-based calibration solution for electrospray ionization (ESI)-MSwas developed, intended for peptide analysis. With a larger number ofsignals in the m/z range of interest, precision, and probably accuracy,improved compared to a commercial calibration solution.In Paper IV, calibration options for ESI-MS were reviewed. Factorsaffecting accuracy and precision, in general and for different instruments,were summarized, and a comprehensive list of calibrants was compiled.Paper V further investigated accuracy and precision in MS, specificallyregarding chemical mass shifts in ion traps. It was shown that clusters andsome adduct ions would be unsuitable for calibration of ion traps, and thatlinear ion traps showed mass shifts similar to spherical ion traps.
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| 12. |
- Xie, Sheng, et al.
(författare)
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Design and synthesis of theranostic antibiotic nanodrugs that display enhanced antibacterial activity and luminescence
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 114:32, s. 8464-8469
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Tidskriftsartikel (refereegranskat)abstract
- We report the modular formulation of ciprofloxacin-based pure theranostic nanodrugs that display enhanced antibacterial activities, as well as aggregation-induced emission (AIE) enhancement that was successfully used to image bacteria. The drug derivatives, consisting of ciprofloxacin, a perfluoroaryl ring, and a phenyl ring linked by an amidine bond, were efficiently synthesized by a straightforward protocol from a perfluoroaryl azide, ciprofloxacin, and an aldehyde in acetone at room temperature. These compounds are propeller-shaped, and upon precipitation into water, readily assembled into stable nanoaggregates that transformed ciprofloxacin derivatives into AIE-active luminogens. The nanoaggregates displayed increased luminescence and were successfully used to image bacteria. In addition, these nanodrugs showed enhanced antibacterial activities, lowering the minimum inhibitory concentration (MIC) by more than one order of magnitude against both sensitive and resistant Escherichia coli. The study represents a strategy in the design and development of pure theranostic nanodrugs for combating drug-resistant bacterial infections.
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| 13. |
- Zhou, Yuye, et al.
(författare)
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An antibody-free sample pretreatment method for osteopontin combined with MALDI-TOF MS/MS analysis
- 2019
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 14:3
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Tidskriftsartikel (refereegranskat)abstract
- Osteopontin is an osteoblast-secreted protein with an aspartic acid-rich, highly phosphorylated, and glycosylated structure. Osteopontin can easily bind to integrins, tumor cells, extracellular matrix and calcium, and is related to bone diseases, various cancers, inflammation etc. Here, DEAE-Cibacron blue 3GA was used to extract recombinant osteopontin from human plasma, and to deplete abundant plasma proteins with an antibody-free method. Using selected buffer systems, osteopontin and human serum albumin could be bound to DEAE-Cibacron blue 3GA, while immunoglobulin G was excluded. The bound osteopontin could then be separated from albumin by using different sequential elution buffers. By this method, 1 μg/mL recombinant osteopontin could be separated from the major part of the most abundant proteins in human plasma. After trypsin digestion, the extracted osteopontin could be successfully detected and identified by MALDI-TOF MS/MS using the m/z 1854.898 peptide and its fragments.
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