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Subcellular chemical imaging of structurally similar acridine drugs by near-field laser desorption/laser postionization mass spectrometry
摘要： Insights into the pharmacologic effect on cellular processes and the potential toxicological effects are vital to new drug development and evaluation, yet research on these subjects remains a great challenge due to the lack of information regarding the spatiotemporal distribution of drugs and metabolites within a single cell. Mass spectrometry imaging (MSI) has proven to be a label-free and high-throughput approach for visualizing drug distribution in spatial and temporal domains. However, single-cell drug imaging has been limited so far by detection sensitivity and microscale lateral resolution. Herein, we report near-field laser desorption/laser postionization mass spectrometry (NDPI-MS) for single-cell imaging of two structurally similar drugs, proflavine and ethacridine, and subcellular distributions of proflavine at different drug concentrations were investigated. The NDPI-MS imaging results indicate that proflavine was accumulated in lysosomes, which was verified by laser scanning confocal microscopy (LSCM). Additionally, a distinguished subcellular distribution pattern of ethacridine from proflavine could be visualized, highlighting the complexity of the interaction between the drugs and biological environment even though these two drugs possess similar structures. Taken together, the present results demonstrate the great potential of the integrated single-cell MSI platform for characterizing the drug distribution and its phenotype changes within individual cells, expediting the identification and evaluation of newly developed drugs.
关键词： single cell imaging,mass spectrometry,acridine drugs,laser postionization,near-field
更新于2025-09-23 15:19:57
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A Simple Method for the Evaluation of the Pulse Width of an Ultraviolet Femtosecond Laser Used in Two-Photon Ionization Mass Spectrometry
摘要： A simple method was proposed for on-site evaluation of the pulse width of an ultraviolet femtosecond laser coupled with a mass spectrometer. This technique was based on measurement of a two-photon ionization signal in mass spectrometry by translation of the prism in the pulse compressor of the femtosecond laser. The method was applied to optical pulses that were emitted at wavelengths of 267, 241, and 219 nm; the latter two pulses were generated by four-wave Raman mixing using the third harmonic emission of a Ti:sapphire laser (267 nm) in hydrogen gas. The measurement results show that this approach is useful for evaluation of the pulse width of the ultraviolet femtosecond laser used in mass spectrometry for trace analysis of organic compounds.
关键词： pulse width,mass spectrometry,ultraviolet femtosecond laser,ionization
更新于2025-09-23 15:19:57
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Determination of chondroitin sulfate in synovial fluid and drug by ratiometric fluorescence strategy based on carbon dots quenched FAM-labeled ssDNA
摘要： Chondroitin sulfate (CS) plays an increasingly important role in clinical settings and pharmacy quality control. However, sensitive and simple methods for CS detection remain limited. In this work, positively charged nitrogen doped carbon dots (P-NCDs) with internal luminescence and quenching property to FAM-labeled random-sequence ssDNA (F-ssDNA) were prepared by a simple heating method. P-NCDs attached and quenched F-ssDNA through electrostatic interaction to form the system of P-NCDs and F-ssDNA (P-NCDs/F-ssDNA) with retained fluorescence intensity of P-NCDs. The highly negatively charged CS reacted electrostatically with P-NCDs and then replaced F-ssDNA in P-NCDs/F-ssDNA to recover the fluorescence intensity of the original quenched F-ssDNA while retaining the internal fluorescence intensity of P-NCDs. Thus, by using restored F-ssDNA as the signal controlled by adding CS to P-NCDs/F-ssDNA, a ratiometric fluorescence strategy based on the retained fluorescence of P-NCDs as reference signal was fabricated through synchronous fluorescence spectrometry for the sensitive detection of CS. Under the optimal experimental conditions, a linear equation for CS was obtained for CS concentration within the range of 0.05–2.0 μg/mL. The method was also successfully applied for the accurate determination of CS in joint fluid samples of arthritic patients, chondroitin sulfate tablets, and chondroitin sulfate eye drops, suggesting its appreciable application potential in the clinic.
关键词： Positively charged nitrogen doped carbon dots (P-NCDs),Chondroitin sulfate,Synchronous fluorescence spectrometry,Ratiometric fluorescence strategy,Synovial fluid
更新于2025-09-23 15:19:57
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Study of multilayer polymer materials after ionization treatment
摘要： Electron-beam technologies of food products processing involves the use of modern packaging materials in form of polymer films of different composition. The objective of the research is to study the impact of accelerated electrons on the structure of the polymeric packaging materials used for storage of agricultural products. It was investigated radiation exposure on film material PE/PA (80/20) with a thickness of 80 mkm. This film used for storage of vegetables and fruits and has the necessary indicators for gas and vapor permeability. Electron beam treatment of the films was performed on a compact radiation sterilization installation with local bio-protection with electron energy of 5 MeV. A polymer films were irradiated with doses from 1 to 10 kGy. Changing the structure of the film composition was monitored by IR spectrometry. As a result of irradiation by accelerated electrons with doses up to 18 kGy is established that the polymer film is modification of the polymeric material in the form of a partial degradation with subsequent intra-molecular cross-linking. This improves the physico-mechanical properties in the transverse direction, and such film can be used for food packaging before electron-beam treatment.
关键词： electron-beam technologies,radiation exposure,IR spectrometry,accelerated electrons,polymer films
更新于2025-09-23 15:19:57
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Impact of Tryptophan Oxidation in Complementarity-Determining Regions of Two Monoclonal Antibodies on Structure-Function Characterized by Hydrogen-Deuterium Exchange Mass Spectrometry and Surface Plasmon Resonance
摘要： Purpose Tryptophan’s (Trp) unique hydrophobic and structural properties make it an important antigen binding motif when positioned in complementarity-determining regions (CDRs) of monoclonal antibodies (mAbs). Oxidation of Trp residues within the CDR can deleteriously impact antigen binding, particularly if the CDR conformation is altered. The goal of this study was to evaluate the conformational and functional impact of Trp oxidation for two mAb subtypes, which is essential in determining the structure-function relationship and establishing appropriate analytical control strategies during protein therapeutics development. Methods Selective Trp oxidation was induced by 2,2′-Azobis(2-amidinopropane) dihydrochloride (AAPH) treatment in the presence of free methionine (Met). The native and chemically oxidized mAbs were characterized by hydrogen-deuterium exchange mass spectrometry (HDX-MS) for conformational changes and surface plasmon resonance (SPR) for antigen-antibody binding. Results Treatment of mAbs with AAPH selectively oxidized solvent accessible Trp residues. Oxidation of Trp within or in proximity of CDRs increased conformational flexibility in variable domains and disrupted antigen binding. Conclusions Trp oxidation in CDRs can adversely impact mAbs’ conformation and antigen binding. Trp oxidation should be carefully evaluated as part of critical quality attribute assessments. Oxidation susceptible Trp should be closely monitored during process development for mAbs to establish appropriate analytical control for manufacturing of drug substance and drug product.
关键词： Tryptophan oxidation,surface plasmon resonance,complementarity-determining region,hydrogen-deuterium exchange mass spectrometry,monoclonal antibody
更新于2025-09-23 15:19:57
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Reconstruction of X-rays spectra of clinical linear accelerators from transmission data with generalized simulated annealing
摘要： The spectral distribution of megavoltage X-rays used in radiotherapy departments is a fundamental quantity from which, in principle, all relevant information required for radiotherapy treatments can be determined. The direct measurement is di?cult to achieve clinically and analyzing the transmission is a clinically viable indirect method for determining clinical linear accelerators photon spectra. In this method, transmission signals are acquired after the beam passes through di?erent thicknesses of attenuators. The objective of this work was the establishment and application of an indirect method that used a spectral model based on generalized simulated annealing algorithm to determine the spectrum of clinical linear accelerators photons based on the transmission curve. Analysis of the spectra was made by analytical determination of dosimetric quantities and related parameters.
关键词： Spectrometry,Photons,Radiotherapy,Monte Carlo,Generalized simulated annealing
更新于2025-09-23 15:19:57
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Neon plasma for effective ionisation of oxygen and fluorine in pulsed glow discharge – high ionisation energy elements quantification in potassium titanyl phosphate single crystals
摘要： Neon glow discharge was tested for the direct analysis of solid dielectric materials by pulsed glow discharge time-of-flight mass spectrometry with an emphasis on the elements with high ionisation energy. The findings for neon were compared to conventional argon glow discharge. Fluorine doped potassium titanyl phosphate (KTP) single crystals were used for analysis. The following parameters were optimised: repelling pulse delay, discharge duration and voltage and pressure in the discharge cell. Relative sensitivity factors were used for quantification; titanium was used for normalisation. Similar to argon glow discharge, the most effective mechanism for fluorine and oxygen ionisation was found to be attributed to high-energy electrons under short repelling pulse delays. Penning ionisation of oxygen in neon glow discharge was found to be less efficient. Overall, the use of neon significantly benefited fluorine and oxygen determination; the limits of detection for oxygen (0.0005 mass %) and fluorine (0.0002 mass %) decreased several times compared to argon glow discharge (0.001 and 0.01 mass %, respectively) as a result of more effective ionisation. The improvement was especially pronounced for fluorine, due to the alleviation of plasma-based interferences. However, for other KTP constituents – potassium, phosphorus and titanium – the analytical performance was expectedly lower, due to the lower sputtering rates in neon glow discharge. The limits of detection for potassium and phosphorus were significantly increased, being 0.008 mass % and 0.01 mass %, respectively. Notably, the performance for non-high ionisation energy elements was adequate for their single-run quantification along with oxygen and fluorine at non-trace levels. Thus, the use of neon as discharge medium for pulsed glow discharge mass spectrometry is clearly justified for the determination of high ionisation energy elements such as oxygen and fluorine in non-conducting matrices.
关键词： oxygen,mass spectrometry,neon,direct determination,fluorine,pulsed glow discharge
更新于2025-09-19 17:15:36
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Detection of Metabolic Changes Induced via Drug Treatments in Live Cancer Cells and Tissue Using Raman Imaging Microscopy
摘要： Isocitrate dehydrogenase 1 (IDH1) mutations in gliomas, fibrosarcoma, and other cancers leads to a novel metabolite, D-2-hydroxyglutarate, which is proposed to cause tumorigenesis. The production of this metabolite also causes vulnerabilities in cellular metabolism, such as lowering NADPH levels. To exploit this vulnerability, we treated glioma and fibrosarcoma cells that harbor an IDH1 mutation with an inhibitor of nicotinamide adenine dinucleotide (NAD+) salvage pathway, FK866, and observed decreased viability in these cells. To understand the mechanism of action by which the inhibitor FK866 works, we used Raman imaging microscopy and identified that proteins and lipids are decreased upon treatment with the drug. Raman imaging showed a different distribution of lipids throughout the cell in the presence of the drug compared with the untreated cells. We employed nuclear magnetic resonance NMR spectroscopy and mass spectrometry to identify the classes of lipids altered. Our combined analyses point to a decrease in cell division due to loss of lipid content that contributes to membrane formation in the in vitro setting. However, the FK866 drug did not have the same potency in vivo. The use of Raman imaging microscopy indicated an opposite trend of lipid distribution in the tissue collected from treated versus untreated mice when compared with the cells. These results demonstrate the role of Raman imaging microscopy to identify and quantify metabolic changes in cancer cells and tissue.
关键词： NAD+ synthesis,tissue imaging,single cell imaging,microscopy,Raman spectrometry,fibrosarcoma IDH1
更新于2025-09-19 17:15:36
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A direct and safe method for plutonium determination using total reflection X-ray fluorescence spectrometry
摘要： A direct, simple and safe micro-analytical method for the determination of plutonium (Pu) using Total Reflection X-ray Fluorescence (TXRF) spectrometry is reported for the first time. The TXRF specimens were made by depositing sample solution aliquots containing 100–160 ng of Pu on quartz sample supports. The TXRF specimens of Pu, thus prepared after drying, were further isolated by dropcasting 10% collodion solution in amyl acetate on the sample spots. This novel methodology fixes Pu on TXRF supports, thus avoiding loose radioactive particles in TXRF specimens. These operations were carried out inside a fume hood. Since the analyte amount required for analysis was in ng levels, Pu particles fixed on the supports were in a non-dispersible form and the analysis was performed without touching the sample spot, there was no risk of Pu contamination, when these specimens were handled in the ambient atmosphere. The developed methodology showed the average precision of TXRF values as 3% (1s, n = 3) and the average deviation of TXRF determined values from the expected values was 6% with a sample size of 100–160 ng of Pu and measurement time of 2000 seconds. The detection limit for Pu was 0.4 ng. The studies resulted in the development of a TXRF compositional characterization method for precious, hazardous and radioactive samples without putting the instrument inside a glove box and thus, avoiding complicated handling of the spectrometer inside the glove box as well as minimizing the sample amount, radiation dose and the radioactive waste generation.
关键词： plutonium determination,TXRF spectrometry,micro-analytical method,radioactive samples,collodion isolation
更新于2025-09-19 17:15:36
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Раrаdохical Sесоndаrу Emissiоn Mаss Sресtrum оf thе Lеuсо Fоrm оf Mеthуlеnе Bluе
摘要： A paradoxical relation between the secondary emission mass spectra of Methylene Blue and its leuco form is revealed: in the mass spectrum of the dye cation Cat+ (oxidized form with the molecular weight 284), an intense product of its reduction with m/z 285 is recorded, while the mass spectrum of the leuco dye (reduced form with the molecular weight 285) corresponds to an oxidized form with a dominating peak at m/z 284. An explanation of this empirical fact is proposed: the redox reactions induced by ionizing factors under the conditions of secondary emission experiments pass in the direction permitted for the particular initial form of the redox-active compound. Namely, an oxidized form undergoes reduction, whereas the reduced form is oxidized. This effect should be taken into account for the correct identification of redox-active compounds by their secondary emission mass spectra and for simulating redox reactions in the systems containing redox-active dyes under mass spectrometric conditions.
关键词： leuco form,Methylene Blue cationic dye,secondary emission mass spectrometry,redox reactions
更新于2025-09-19 17:15:36