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This work experimentally verifies and proves the two long since postulated matrix-assisted laser desorption/ionization (MALDI)
analyte protonation pathways known as the Lucky Survivor and the gas phase protonation model. Experimental differentiation
between the predicted mechanisms becomes possible by the use of deuterated matrix esters as MALDI matrices, which are stable
under typical sample preparation conditions and generate deuteronated reagent ions, including the deuterated and deuteronated
free matrix acid, only upon laser irradiation in the MALDI process. While the generation of deuteronated analyte ions proves
the gas phase protonation model, the detection of protonated analytes by application of deuterated matrix compounds without
acidic hydrogens proves the survival of analytes precharged from solution in accordance with the predictions from the Lucky
Survivor model. The observed ratio of the two analyte ionization processes depends on the applied experimental parameters
as well as the nature of analyte and matrix. Increasing laser fluences and lower matrix proton affinities favor gas phase
protonation, whereas more quantitative analyte protonation in solution and intramolecular ion stabilization leads to more
Lucky Survivors. The presented results allow for a deeper understanding of the fundamental processes causing analyte ionization
in MALDI and may alleviate future efforts for increasing the analyte ion yield. 相似文献
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Fuchs SW Proschak A Jaskolla TW Karas M Bode HB 《Organic & biomolecular chemistry》2011,9(9):3130-3132
Thirteen novel PAX (peptide-antimicrobial-Xenorhabdus) peptides were identified in Xenorhabdus nematophila HGB081. Their structures including the absolute configuration were elucidated using a combination of labeling experiments, detailed MS/MS experiments, the advanced Marfey's method, and a detailed analysis of the biosynthesis gene cluster, which was identified as well. 相似文献
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In a recent paper (Setz, P. D.; Knochenmuss, R. Phys. Chem. A2005, 109, 4030-4037) energy-transfer from excited matrix molecules to fluorescent traps was used to study the role of pooling reactions for the ionization processes in matrix-assisted laser desorption ionization (MALDI) using 2,5-dihydroxybenzoic acid as matrix. Exciton trapping was shown to interfere with matrix ionization. These investigations were extended to analyze the influence of fluorescent traps on both matrix and analyte ions for alpha-cyano-4-hydroxycinnamic acid and further matrices. A strong influence of the fluorescent traps on both matrix and analyte ionization was revealed, depending on the matrix:trap ratio, and manifested itself differently for low and high mass analytes. The observations are rationalized by the intermediate formation of a "hot spot" due to an efficient conversion of electronic excitation energy to vibronic energy within the fluorescent traps. This process favors the desorption and ionization of small vaporizable analytes and compromises the cluster ablation process needed for larger analyte ions. 相似文献
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Thorsten Jaskolla Beate Fuchs Michael Karas Jürgen Schiller 《Journal of the American Society for Mass Spectrometry》2009,20(5):867-874
Phosphatidylethanolamines (PEs) are abundant lipid constituents of the cellular membrane. The amino group of PEs exhibits
high reactivity with hypochlorous acid that is generated under inflammatory conditions in vivo. The analysis of the resulting
PE mono- and dichloramines is of significant interest since these species represent important mediators of lipid peroxidation.
We have shown in a previous communication that mass spectrometric detection of PE chloramines is only possible with ESI MS,
whereas MALDI-TOF MS fails to detect these products if standard matrices are used. 相似文献
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Marcel Wiegelmann Jens Soltwisch Thorsten W. Jaskolla Klaus Dreisewerd 《Analytical and bioanalytical chemistry》2013,405(22):6925-6932
A high analytical sensitivity in ultraviolet matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is only achieved if the laser wavelength corresponds to a high optical absorption of the matrix. Laser fluence and the physicochemical properties of the compounds, e.g., the proton affinity, also influence analytical sensitivity significantly. In combination, these parameters determine the amount of material ejected per laser pulse and the ion yield, i.e., the fraction of ionized biomolecules. Here, we recorded peptide ion signal intensities as a function of these parameters. Three cinnamic acid matrices were investigated: α-cyano-4-hydroxycinnamic acid, α-cyano-4-chlorocinnamic acid, and α-cyano-2,4-difluorocinnamic acid. In addition, 2,5-dihydroxybenzoic acid was used in comparison experiments. Ion signal intensities “per laser shot” and integrated ion signal intensities were acquired over 900 consecutive laser pulses applied on distinct positions on the dried-droplet sample preparations. With respect to laser wavelength, the two standard MALDI wavelengths of 337/355 nm were investigated. Also, 305 or 320 nm was selected to account for the blue-shifted absorption profiles of the halogenated derivatives. Maximal peptide ion intensities were obtained if the laser wavelength fell within the peak of the absorption profile of the compound and for fluences two to three times the corresponding ion detection threshold. The results indicate ways for improving the analytical sensitivity in MALDI-MS, and in particular for MALDI-MS imaging applications where a limited amount of material is available per irradiated pixel. 相似文献
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Thorsten W. Jaskolla Michael Karas Udo Roth Kerstin Steinert Christoph Menzel Karsten Reihs 《Journal of the American Society for Mass Spectrometry》2009,20(6):1104-1114
The properties of several cinnamic acid compounds used as matrices for matrix-assisted laser desorption ionization time-of-flight
mass spectrometry (MALDI-TOF MS) were investigated as standard dried droplet (DD) and vacuum sublimed preparations. The differences
between both preparation methods were analyzed with regard to matrix grain size, internal ion energy, initial velocity, analyte
intensity, and analyte incorporation depth. Some of the used cinnamic acid derivatives exhibit clearly reduced grain sizes
as sublimed preparations compared with standard DD approaches. In these cases higher effective temperatures could be measured
accompanied by increased analyte intensities, which can be explained by stronger volatilization processes caused by a hindered
heat dissipation resulting in a raised analyte transfer into the gas phase. For all sublimed compounds, a strong increase
of the initial ion velocity compared with DD preparations could be measured. Higher initial ion velocities correlate with
a decrease in internal ion energy which might be attributed to the very uniform crystal morphology exhibited by sublimed compounds.
For sublimed matrices without reduced grain size, at least slightly higher analyte intensities could be detected at raised
laser fluences. Analyte accumulation in the uppermost matrix layers or the detected higher ion stability can be explanations
for these results. 相似文献
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