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Estimation of Flexible and Rigid Residues of Disulfide-Bridged and Phosphorylated Proteins Using Matrix-Assisted Laser Desorption/Ionization in-Source Decay Mass Spectrometry
摘要： Flexible and rigid residues in disul?de-bridged and phosphorylated proteins have been estimated by using MALDI in-source decay mass spectrometry (ISD MS). The MALDI-ISD spectra of bovine α-lactoalbumin, β-lactoglobulin A, and β-casein predict that the backbone amide of Xxx-Asp/Asn/Cys/Ser/pSer and Gly-Xxx residues has higher hydrogen accessibility than other residues, while Xxx-Ile/Val residues have less accessibility. The higher hydrogen-accessible and lower accessible residues as measured by MALDI-ISD are consistent with the ?exible and rigid residues determined by X-ray, nuclear magnetic resonance, and ?uorescence decay methods. The disul?de bridges and phosphate groups do not prevent the estimation of ?exible or rigid residues, whereas some other disul?de bridges inhibit the identi?cation because of decreased sensitivity of ISD fragment ions. The estimation of ?exible and rigid residues by means of the matrix-hydrogen accessibility can be explained by exposure or lack thereof to the hydrogen-accessible sites of intact proteins. It is proposed that MALDI-ISD is a powerful tool for identifying ?exible and rigid residues of posttranslational modi?ed proteins without the conformation information of the protein data bank.
关键词： flexible and rigid residues,phosphorylated proteins,disul?de-bridged proteins,hydrogen accessibility,MALDI in-source decay mass spectrometry
更新于2025-09-12 10:27:22
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Mass separated particle flux from a laser-ablation metal cluster source
摘要： Flux waveforms of aluminum cluster beams supplied from a laser-ablation cluster source were precisely investigated under various source conditions such as background pressure, ablation laser intensity, and nozzle structure. A time-of-flight mass spectroscopy revealed that aluminum clusters with sizes up to 200 were generated and the amount of the clusters could be maximized by choosing a proper background pressure (～2 MPa) and an ablation laser fluence (～40 mJ/cm2). Flux waveforms of clusters having specific sizes were carefully reconstructed from the observed mass spectra. It is found that the pulse widths of the aluminum cluster beams were typically about 100 μs and much smaller than that of the monoatomic aluminum beam, indicating that the cluster formation was limited in a relatively small volume in the laser-ablated vapor. Introducing a conical nozzle having a large open angle was also found to enhance the cluster beam velocity and reduce its pulse width. A velocity measurement of particles in the cluster beam was conducted to examine the velocity spread of the supplied clusters. We found that the aluminum clusters were continuously released from the source for about 100 μs and this release time mainly determined the pulse width of the cluster beam, suggesting that controlling the behavior of an ablated vapor plume in the waiting room of the cluster source holds the key to drastically improving the cluster beam flux.
关键词： mass spectrometry,laser ablation,molecular beam,Cluster
更新于2025-09-12 10:27:22
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Matrix Assisted Laser Desorption Ionization-Time-of-Flight mass spectrometry identification of <i>Mycobacterium bovis </i>in Bovinae
摘要： In this study, Matrix Assisted Laser Desorption Ionization-Time-of-Flight (MALDI-TOF) mass spectrometry was used to identify Mycobacterium bovis from cattle and buffalo tissue isolates from the North and South regions of Brazil, grown in solid medium and previously identified by Polymerase Chain Reaction (PCR) based on Region of Difference 4 (RD4), sequencing and spoligotyping. For this purpose, the protein extraction protocol and the mass spectra reference database were optimized for the identification of 80 clinical isolates of mycobacteria. As a result of this optimization, it was possible to identify and differentiate M. bovis from other members of the Mycobacterium tuberculosis complex with 100% specificity, 90.91% sensitivity and 91.25% reliability. MALDI-TOF MS methodology described herein provides successful identification of M. bovis within bovine/bubaline clinical samples, demonstrating its usefulness for bovine tuberculosis diagnosis in the future.
关键词： Matrix Assisted Laser Desorption Ionization-Time-of-Flight (MALDI-TOF) mass spectrometry,bovine tuberculosis,Mycobacterium tuberculosis complex,Mycobacterium bovis
更新于2025-09-12 10:27:22
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Definitive production of intact organic pentacation radical: Octafluoronaphthalene ionized in intense femtosecond laser fields
摘要： We demonstrate the production of long-lived octafluoronaphthalene pentacation radical in gas phase by tunneling ionization using 1.4 μm femtosecond laser pulses. Multiply charged molecular cations are definitively identified by their m/z, isotopic structure, and peak shape using time-of-flight mass spectrometry. The tetracation yield relative to the trication radical yield is 0.33 that is the highest value obtained to date. The yield of pentacation radical relative to tetracation is 0.025. Our results show that the use of perfluoro-aromatics is the promising way to approach intact highly charge states.
关键词： Tunnel ionization,Time-of-flight,Mass spectrometry,Femtosecond laser
更新于2025-09-12 10:27:22
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Proteomics of human glomerulonephritis by laser microdissection and liquid chromatography‐tandem mass spectrometry
摘要： Aim: Laser microdissection (LMD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) enable clinicians to analyse proteins from tissue sections. In nephrology, these methods are used to diagnose diseases of abnormal protein deposition, such as amyloidosis, but they are seldom applied to the diagnosis and pathophysiological understanding of human glomerular diseases. Methods: Renal biopsy specimens were obtained from five patients with IgA nephropathy (IgAN), five patients with membranous nephropathy (MN) and five kidney transplant donors (as controls). From 10-μm-thick sections of formalin-fixed, paraffin-embedded specimens, 0.3-mm2 samples of glomerular tissue were subjected to LMD. The samples were analysed by LC-MS/MS and investigated clinically and histologically. Results: From the control glomeruli, we identified more than 300 types of proteins. In patients with IgAN, we detected significant increases not only in IgA1 and in C3 but also in the factors related to oxidative stress and cell proliferation in comparison to the controls. In patients with MN, levels of IgG1, IgG4, C3, C4a, and phospholipase-A2-receptor were significantly elevated in comparison to the controls, as were the aforementioned factors related to oxidative stress and cell proliferations detected in IgAN. Conclusion: Application of LMD and LC-MS/MS to renal biopsy specimens enabled us to identify not only pathognomonic proteins for the diagnosis but also several factors possibly involved in the pathogenesis of human glomerular diseases.
关键词： glomerulonephritis,IgA nephropathy,membranous nephropathy,laser microdissection,mass spectrometry
更新于2025-09-12 10:27:22
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Three-Dimensional Composition Analysis of SnAg Solder Bumps Using Ultraviolet Femtosecond Laser Ablation Ionization Mass Spectrometry
摘要： The application of a novel UV fs Laser Ablation Ionization Mass Spectrometry approach for chemical depth profiling of low-melting point, high surface roughness SnAg solder bump features is presented. The obtained resolved three-dimensional compositional submicrometer data reveal unprecedented information on the distribution of individual elements inside the solder bump matrix. Moreover, the determination of matrix-matched relative sensitivity coefficients allows the first report on quantitative assessment of the SnAg alloy composition. These results significantly contribute to an in-depth understanding of the SnAg plating process. This experimental procedure may find application in future additive performance screening.
关键词： three-dimensional compositional analysis,chemical depth profiling,SnAg solder bumps,UV fs Laser Ablation Ionization Mass Spectrometry,matrix-matched relative sensitivity coefficients
更新于2025-09-12 10:27:22
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Laser Ablation Electrospray Ionization Time-of-Flight Mass Spectrometry for Direct Analysis of Biological Tissue
摘要： Direct analysis and identi?cation of biological tissue is signi?cant for clinical applications. In this study, porcine liver and kidney have been analyzed using laser ablation electrospray ionization time-of-?ight mass spectrometry (LAESI-TOFMS). This method showed good reproducibility for the same types of tissue and is capable of distinguishing di?erent tissue species. The margin assessment was also performed using porcine renal tissue, and the response time was less than 6 s. Furthermore, human hepatocarcinoma tissue and normal tissue were identi?ed using this method. Our results indicate that LAESI-TOFMS is a feasible approach for direct identi?cation of tumor tissue and potential for assessment of the resection margin.
关键词： Laser ablation electrospray ionization mass spectrometry,biological tissue,margin assessment,tumor identification
更新于2025-09-12 10:27:22
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Tissue classification by rapid evaporative ionization mass spectrometry (REIMS): comparison between a diathermic knife and CO2 laser sampling on classification performance
摘要： The increasing need for rapid, in situ, and robust tissue profiling approaches in the context of intraoperative diagnostics has led to the development of a large number of ambient ionization-based surface sampling strategies. This paper compares the performances of a diathermic knife and a CO2 laser handpiece, both clinically approved, coupled to a rapid evaporative ionization mass spectrometry (REIMS) source for quasi-instantaneous tissue classification. Several fresh meat samples (muscle, liver, bone, bone marrow, cartilage, skin, fat) were obtained from different animals. Overall, the laser produced cleaner cuts and more reproducible and higher spectral quality signals when compared with the diathermic knife (CV laser = 9–12%, CV diathermic = 14–23%). The molecular profiles were subsequently entered into a database and PCA/LDA classification/prediction models were built to assess if the data generated with one sampling modality can be employed to classify the data generated with the other handpiece. We demonstrate that the correct classification rate of the models increases (+ 25%) with the introduction of a model based on peak lists that are tissue-specific and common to the two handpieces, compared with considering solely the whole molecular profile. This renders it possible to use a unique and universal database for quasi-instantaneous tissue recognition which would provide similar classification results independent of the handpiece used. Furthermore, the laser was able to generate aerosols rich in lipids from hard tissues such as bone, bone marrow, and cartilage. Combined, these results demonstrate that REIMS is a valuable and versatile tool for instantaneous identification/classification of hard tissue and coupling to different aerosol-generating handpieces expands its field of application.
关键词： Bioanalytical methods,Tissue analysis,Laser ablation,Mass spectrometry,REIMS,Lipids
更新于2025-09-12 10:27:22
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Red‐Blood‐Cell Waveguide as a Living Biosensor and Micromotor
摘要： The changes of flavor components during boiling in Lentinus edodes were studied by high-performance liquid chromatography and gas chromatography-mass spectrometry in this article. Results showed that nonvolatile flavor components in L. edodes gradually transferred into the soup during boiling. Contents of nonvolatile flavor substances in the soup increased significantly (p < .05) compared with the preboiling period (15 minutes) and gradually maintained a balanced situation with the boiling time extended. During boiling, content of alcohols gradually reduced, especially the content of 1-octen-3-ol, which is a typical flavor component in L. edoedes. The contents of sulfur compounds, aldehydes, and hydrocarbons increased first and finally decreased gradually with the boiling time extended. Therefore, the changes of flavor components in the soup almost maintained a balanced situation with the boiling time from 30 to 60 minutes. The results of this article could provide a theoretical basis for the changes of flavor compounds in L. edodes during boiling.
关键词： flavor components,gas chromatography–mass spectrometry,High-performance liquid chromatography,boiling,Lentinus edodes
更新于2025-09-11 14:15:04
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Internal Energy Deposition in Infrared Matrix-Assisted Laser Desorption Electrospray Ionization With and Without the Use of Ice as a Matrix
摘要： The internal energy deposited into analytes during the ionization process largely influences the extent of fragmentation, thus the appearance of the resulting mass spectrum. The internal energy distributions of a series of para-substituted benzyl pyridinium cations in liquid and solid-state generated by infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) were measured using the survival yield method, of which results were subsequently compared with conventional electrospray ionization (ESI). The comparable mean internal energy values (e.g., 1.8–1.9 eV at a collision energy of 15 eV) and peak widths obtained with IR-MALDESI and ESI support that IR-MALDESI are essentially a soft ionization technique where analytes do not gain considerable internal energy during the laser-induced desorption process and/or lose energy during uptake into charged electrospray droplets. An unusual fragment ion, protonated pyridine, was only found for solid IR-MALDESI at relatively high collision energies, which is presumably resulted from direct ionization of the pre-charged analytes in form of salts. Analysis of tissue with an ice layer consistently yielded ion populations with higher internal energy than its counterpart without an ice layer, likely due to a substantially enhanced number of IR absorbers with ice. Further measurements with holo-myoglobin show that IR-MALDESI-MS retains the noncovalently bound heme-protein complexes under both native-like and denaturing conditions, while complete loss of the heme group occurred in denaturing ESI-MS, showing that the softness of IR-MALDESI is equivalent or superior to ESI for biomolecules.
关键词： Ambient ionization,Survival yield method,Internal energy deposition,Mass spectrometry imaging,Thermometer ions,IR-MALDESI
更新于2025-09-11 14:15:04