Desorption Electrospray Ionization Mass Spectrometry Research Articles

Improved Detection of Tryptic Peptides from Tissue Sections Using Desorption Electrospray Ionization Mass Spectrometry Imaging.

DESI-MSI is an ambient ionization technique used frequently for the detection of lipids, small molecules, and drug targets. Until recently, DESI had only limited use for the detection of proteins and peptides due to the setup and needs around deconvolution of data resulting in a small number of species being detected at lower spatial resolution. There are known differences in the ion species detected using DESI and MALDI for nonpeptide molecules, and here, we identify that this extends to proteomic species. DESI MS images were obtained for tissue sections of mouse and rat brain using a precommercial heated inlet (approximately 450 °C) to the mass spectrometer. Ion mobility separation resolved spectral overlap of peptide ions and significantly improved the detection of multiply charged species. The images acquired were of pixel size 100 μm (rat brain) and 50 μm (mouse brain), respectively. Observed tryptic peptides were filtered against proteomic target lists, generated by LC-MS, enabling tentative protein assignment for each peptide ion image. Precise localizations of peptide ions identified by DESI and MALDI were found to be comparable. Some spatially localized peptides ions were observed in DESI that were not found in the MALDI replicates, typically, multiply charged species with a low mass to charge ratio. This method demonstrates the potential of DESI-MSI to detect large numbers of tryptic peptides from tissue sections with enhanced spatial resolution when compared to previous DESI-MSI studies.

The discovery of regional neurotoxicity-associated metabolic alterations induced by carbon quantum dots in brain of mice using a spatial metabolomics analysis

BackgroundRecently, carbon quantum dots (CQDs) have been widely used in various fields, especially in the diagnosis and therapy of neurological disorders, due to their excellent prospects. However, the associated inevitable exposure of CQDs to the environment and the public could have serious severe consequences limiting their safe application and sustainable development.ResultsIn this study, we found that intranasal treatment of 5 mg/kg BW (20 µL/nose of 0.5 mg/mL) CQDs affected the distribution of multiple metabolites and associated pathways in the brain of mice through the airflow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) technique, which proved effective in discovery has proven to be significantly alerted and research into tissue-specific toxic biomarkers and molecular toxicity analysis. The neurotoxic biomarkers of CQDs identified by MSI analysis mainly contained aminos, lipids and lipid-like molecules which are involved in arginine and proline metabolism, biosynthesis of unsaturated fatty acids, and glutamine and glutamate metabolism, etc. as well as related metabolic enzymes. The levels or expressions of these metabolites and enzymes changed by CQDs in different brain regions would induce neuroinflammation, organelle damage, oxidative stress and multiple programmed cell deaths (PCDs), leading to neurodegeneration, such as Parkinson’s disease-like symptoms. This study enlightened risk assessments and interventions of QD-type or carbon-based nanoparticles on the nervous system based on toxic biomarkers regarding region-specific profiling of altered metabolic signatures.ConclusionThese findings provide information to advance knowledge of neurotoxic effects of CQDs and guide their further safety evaluation.

Exploring Lipid Disturbances and its Spatial Association with α-Synuclein Aggregation in MSA Patient Brain Regions via Desorption Electrospray Ionization Mass Spectrometry Imaging (P5-3.004)

Exploring Lipid Disturbances and its Spatial Association with α-Synuclein Aggregation in MSA Patient Brain Regions via Desorption Electrospray Ionization Mass Spectrometry Imaging (P5-3.004)

Mapping the Metabolic Characteristics and Perturbation of Adult Casper Zebrafish by Ambient Mass Spectrometry Imaging

Casper, a type of transparent mutant-line zebrafish, was generated to overcome the opaque trunk of an adult zebrafish for tumor modeling to realize real-time visualization of transplanted cells in vivo. However, the molecular information at the metabolic level has not received much attention. Herein, a spatially resolved metabolomics method based on an airflow-assisted desorption electrospray ionization–mass spectrometry imaging (AFADESI-MSI) system for whole-body zebrafish was used to investigate small molecules and the distribution of adult casper (Mitfaw2/w2, roya9/a9) and the differences from wild-type zebrafish. Finally, the spatial distribution information of more than 1500 endogenous ions was obtained in positive and negative detection modes, and 186 metabolites belonging to a variety of structural categories were identified or annotated. Compared with wild-type samples, 85 variables, including 37 known metabolites, were screened out. In addition, the disordered metabolic pathways caused by the genetic mutation were excavated, involving downregulation of purine metabolism and arachidonic acid metabolism, upregulation of glycerophospholipid metabolism, and biosynthesis of unsaturated fatty acids. All these results were observed in the most intuitive way through MSI. This study revealed important metabolic characteristics of and perturbation in adult casper zebrafish, and provides indispensable fundamental knowledge for tumor research based on it.

Integration of ion-mobility high-resolution liquid chromatography/mass spectrometry-based untargeted metabolomics and desorption electrospray ionization-mass spectrometry imaging to unveil the ginsenosides variation induced by steaming for Panax ginseng, P. quinquefolius and P. notoginseng

The raw and steamed products of ginseng exhibit different efficacy, and elucidation of the underlying chemical transformation is significant for their rational application and quality control. This work was designed to holistically depict the chemical variation of Panax ginseng (PG), P. quinquefolius (PQ), and P. notoginseng (PN) induced by the steaming, and to unveil the steaming-associated markers diagnostic for differentiating between the raw and processed products, following a three-step strategy: 1) systematic ginsenosides characterization by hybrid scan (namely HDDIDDA) available on the Vion™ ion mobility-quadrupole time-of-flight mass spectrometer coupled with reversed-phase ultra-high performance liquid chromatography; 2) holistic depiction of the chemical variation and discovery of potential markers by the pattern recognition untargeted metabolomics analysis; and 3) construction of steaming-induced transformation network combined with desorption electrospray ionization-mass spectrometry imaging (DESI-MSI). Consequently, 542 ginsenosides were characterized from the raw and processed PG/PQ/PN. Steaming at 1–10 h could cause significant chemical variation, and separately 26, 28, and 18 potential markers were found for the steaming of PG, PQ, and PN. Steaming-induced transformation network mainly involved hydration of the malonyl group, hydrolysis of the glycosyl moiety, and dehydration at C-20. DESI-MSI further revealed spatial distribution of marker saponins in the cork layer, phloem, and xylem, and primarily confirmed the hydrolysis reactions occurring to ginseng steaming. Conclusively, the established strategy is practical to unveil the holistic ginsenosides variation of ginseng induced by the processing, which is useful in the quality control of both the herbal medicines and foods.

Evaluation of Oil-Absorbing Film for Imprint Desorption Electrospray Ionization Mass Spectrometry Imaging (IDESI-MSI) on Biological Samples.

Imprint Desorption Electrospray Ionization Mass Spectrometry Imaging (IDESI-MSI) has proven to be a robust and reliable tool for chemically imaging biological samples such as fungi, animal tissues, and plants, but the choice of the imprint substrate is crucial. It must effectively transfer maximum amounts of species from the sample while preserving the original spatial distribution of detected molecules. In this study, we explored the potential of utilizing an oil-absorbing film, known for its soft nature and excellent lipophilicity, as an imprint substrate for IDESI-MSI on biological samples. To assess the transfer efficiency of the amounts of molecules and molecular patterns, we conducted experiments using mouse brain tissue. The result shows that more than 90% of the analytes can be transferred to the oil-absorbing film from the original tissue. A comparison of IDESI-MSI results between the oil-absorbing film and the original tissue demonstrates the material's capability to transfer most molecules from the original tissue and retain images of different analytes with high spatial fidelity. We extended our investigation to plant imaging, where we applied IDESI-MSI to a cross-section of okra. The oil-absorbing film exhibited promise in this context as well. These findings suggest that IDESI-MSI utilizing the oil-absorbing film holds potential across various research fields, including biological metabolism, chemistry, and clinical research, making this technique widely applicable.

Mass spectrometry-based metabolomics for the elucidation of alkaloid biosynthesis and function in invasive Vincetoxicum rossicum populations

The genus Vincetoxicum includes a couple of highly invasive vines in North America that threaten biodiversity and challenge land management strategies. Vincetoxicum species are known to produce bioactive phenanthroindolizidine alkaloids that might play a role in the invasiveness of these plants via chemical interactions with other organisms. Untargeted, high-resolution mass spectrometry-based metabolomics approaches were used to explore specialized metabolism in Vincetoxicum plants collected from invaded sites in Ontario, Canada. All metabolites corresponding to alkaloids in lab and field samples of V. rossicum and V. nigrum were identified, which collectively contained 25 different alkaloidal features. The biosynthesis of these alkaloids was investigated by the incorporation of the stable isotope-labelled phenylalanine precursor providing a basis for an updated biosynthetic pathway accounting for the rapid generation of chemical diversity in invasive Vincetoxicum. Aqueous extracts of aerial Vincetoxicum rossicum foliage had phytotoxic activity against seedlings of several species, resulting in identification of tylophorine as a phytotoxin; tylophorine and 14 other alkaloids from Vincetoxicum accumulated in soils associated with full-sun and a high-density of V. rossicum. Using desorption-electrospray ionization mass spectrometry, 15 alkaloids were found to accumulate at wounded sites of V. rossicum leaves, a chemical cocktail that would be encountered by feeding herbivores. Understanding the specialized metabolism of V. rossicum provides insight into the roles and influences of phenanthroindolizidine alkaloids in ecological systems and enables potential, natural product-based approaches for the control of invasive Vincetoxicum and other weedy species.

Desorption electrospray ionization mass spectrometry imaging of latent fingerprints revealed by Oil Red O.

To optimize the ionization step independently from surface extraction, the ORO reagent and its mixture with model compounds (triolein and linoleic acid) were first studied in solution using high-resolution electrospray ionization tandem mass spectrometry (ESI-MS/MS). Then, DESI-MSI experiments were performed in both polarity modes for ORO-processed fingermarks deposited on pieces of paper used as porous substrates. ESI-MS of ORO reveals a complex mixture of azo dyes. Two main impurities detected beside the targeted species were characterized using MS/MS and then were usefully employed to produce DESI-MS images of fingermarks, decreasing the scanning rate to get sufficient ion abundance from natural fingerprints. ORO did not prevent chemical profiling, and one major added value of this pink dye was to produce MS images with contrast that cannot be obtained optically for some colored substrates. DESI-MS has demonstrated imaging compatibility with the application of ORO used to enhance latent fingerprints on paper and could also enable chemical profiling in natural fingermarks. In addition, MS images of ORO impurities were of higher quality than optical ones for fingerprints revealed on colored paper.

Carbocation Mechanism Revelation of Molecular Iodine-Mediated Dehydrogenative Aromatization of Substituted Cyclic Ketones to Phenols.

Dehydrogenative aromatization (DA) of cyclic ketones is central to the development of functionalized aromatic precursors and hydrogen transfer-related technologies. Traditional DA strategies require precious metals with oxidants and are typically performed at high temperatures (100-150 °C) to overcome the high energy barrier of aliphatic C-H bond activation. Recently, a mild alternative approach based on I2 has been proposed to realize DA on substituted unsaturated cyclic ketones under ambient conditions. However, depending on the solvent, the product selectivity may vary between phenol ether and phenol, and the reaction mechanisms remain unclear. Herein, based on time-resolved proton nuclear magnetic resonance, DFT calculation, and mass spectrometric analyses, we established a unified mechanism to account for the product distribution. Through substrate scope and desorption electrospray ionization-mass spectrometry, we discovered the formation of a carbocation, which has been overlooked in previous studies. An expanded substrate scope study coupled with spectroscopic observation provided strong evidence to elucidate the formation mechanism and the location of the carbocation. With a renewed understanding of the mechanism, we achieved a phenolic product yield of 17-96% while controlling the selectivity. Moreover, some reactants could undergo DA in H2O, achieving 95-96% yield at below water-boiling temperature.

Mass Spectrometric Imaging of Anionic Phospholipids Desorbed from Human Hippocampal Sections: Discrimination between Temporal and Nontemporal Lobe Epilepsies.

Temporal lobe epilepsy (TLE) is one of the most common neurological disorders, often accompanied by hippocampal sclerosis. The molecular processes underlying this epileptogenesis are poorly understood. To examine the lipid profile, 39 fresh frozen sections of the human hippocampus obtained from epilepsy surgery for TLE (n = 14) and non-TLE (control group; n = 25) patients were subjected to desorption electrospray ionization mass spectrometry imaging in the negative ion mode. In contrast to our earlier report that showed striking downregulation of positively charged phospholipids (e.g., phosphatidylcholine and phosphatidylethanolamine, etc.) in the TLE hippocampus, this study finds complementary upregulation of negatively charged phospholipids, notably, phosphatidylserine and phosphatidylglycerol. This result may point to an active metabolic pool in the TLE hippocampus that produces these anionic phospholipids at the expense of the cationic phospholipids. This metabolic shift could be due to the dysregulation of the Kennedy and CDP-DG pathways responsible for biosynthesizing these lipids. Thus, this study further opens up opportunities to investigate the molecular hallmarks and potential therapeutic targets for TLE.

[Synthesis and tissue distribution of bufadienolides in Bufo bufo gargarizans].

This study explored the biosynthesis of bufadienolides(BDs) in Bufo bufo gargarizans to solve the dilemma of the decreasing resources of B. bufo gargarizans and provide a theoretical basis for the sustainable utilization of the resources. Ultra-high performance liquid chromatography-Orbitrap-mass spectrometry(UHPLC-Orbitrap-MS) was employed to detect the synthesis sites of BDs in B. bufo gargarizans, and the results were verified by desorption electrospray ionization-mass spectrometry imaging(DESI-MSI) and homogenate incubation experiments. BDs in B. bufo gargarizans had the highest content in the liver and the highest concentration in the gallbladder, in addition to the parotid gland and skin, which suggested that the liver could synthesize BDs. The results of DESI-MSI also showed that BDs were mainly enriched in the liver rather than the immature parotid gland. The incubation experiment of liver homogenates demonstrated the liver of B. bufo gargarizans had the ability to synthesize BDs. This study showed that the liver was a major organ for the synthesis of BDs in B. bufo gargarizans during metamorphosis, development, and growth, which provided strong theoretical support for the biosynthesis of BDs and the sustainable utilization of B. bufo gargarizans resources.

Rivastigmine nasal spray for the treatment of Alzheimer’s Disease: Olfactory deposition and brain delivery

Alzheimer’s disease (AD) is characterized by a gradual decline in cognitive function and memory impairment, significantly impacting the daily lives of patients. Rivastigmine (RHT), a cholinesterase inhibitor, is used to treat mild to moderate AD via oral administration. However, oral administration is associated with slow absorption rate and severe systemic side effects. RHT nasal spray (RHT-ns), as a nose-to-brain delivery system, is more promising for AD management due to its efficient brain delivery and reduced peripheral exposure. This study constructed RHT-ns for enhancing AD treatment efficacy, and meanwhile the correlation between drug olfactory deposition and drug entering into the brain was explored. A 3D-printed nasal cast was employed to quantify the drug olfactory deposition. Brain delivery of RHT-ns was quantified using fluorescence tracking and Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) analysis, which showed a good correlation to the olfactory deposition. F2 (containing 1% (w/v) viscosity modifier Avicel® RC-591) with high olfactory deposition and drug brain delivery was further investigated for pharmacodynamics study. F2 exhibited superiority in AD treatment over the commercially available oral formulation. In summary, the present study showed the successful development of RHT-ns with improved olfactory deposition and enhanced brain delivery. It might provide new insight into the design and development of nose-to-brain systems for the treatment of AD.

Evaluation of Inlet Temperature with Three Sprayer Designs for Desorption Electrospray Ionization Mass Spectrometry Tissue Analysis.

Mass spectrometry imaging (MSI) allows for the spatially resolved detection of endogenous and exogenous molecules and atoms in biological samples, typically prepared as thin tissue sections. Desorption electrospray ionization (DESI) is one of the most commonly utilized MSI modalities in preclinical research. DESI ion source technology is still rapidly evolving, with new sprayer designs and heated inlet capillaries having recently been incorporated in commercially available systems. In this study, three iterations of DESI sprayer designs are evaluated: (1) the first, and until recently only, commercially available Waters sprayer; (2) a developmental desorption electro-flow focusing ionization (DEFFI)-type sprayer; and (3) a prototype of the newly released Waters commercial sprayer. A heated inlet capillary is also employed, allowing for controlled inlet temperatures up to 500 °C. These three sprayers are evaluated by comparative tissue imaging analyses of murine testes across this temperature range. Single ion intensity versus temperature trends are evaluated as exemplar cases for putatively identified species of interest, such as lactate and glutamine. A range of trends are observed, where intensities follow either increasing, decreasing, bell-shaped, or other trends with temperature. Data for all sprayers show approximately similar trends for the ions studied, with the commercial prototype sprayer (sprayer version 3) matching or outperforming the other sprayers for the ions investigated. Finally, the mass spectra acquired using sprayer version 3 are evaluated by uniform manifold approximation and projection (UMAP) and k-means clustering. This approach is shown to provide valuable insight that is complementary to the presented univariate evaluation for reviewing the parameter space in this study. Full spectral temperature optimization data are provided as supporting data to enable other researchers to design experiments that are optimal for specific ions.

Unlocking the Molecular Variations of a Micron-Scale Amyloid Plaque in an Early Stage Alzheimer's Disease by a Cellular-Resolution Mass Spectrometry Imaging Platform.

Uncovering the molecular changes at the site where Aβ is deposited plays a critical role in advancing the diagnosis and treatment of Alzheimer's disease. However, there is currently a lack of a suitable label-free imaging method with a high spatial resolution for brain tissue analysis. In this study, we propose a modified desorption electrospray ionization (DESI) mass spectrometry imaging (MSI) method, called segmented temperature-controlled DESI (STC-DESI), to achieve high-resolution and high-sensitivity spatial metabolomics observation by precisely controlling desorption and ionization temperatures. By concentrating the spray plume and accelerating solvent evaporation at different temperatures, we achieved an impressive spatial resolution of 20 μm that enables direct observation of the heterogeneity around a single cell or an individual Aβ plaque and an exciting sensitivity that allows a variety of low-abundance metabolites and less ionizable neutral lipids to be detected. We applied this STC-DESI method to analyze the brains of transgenic AD mice and identified molecular changes associated with individual Aβ aggregates. More importantly, our study provides the first evidence that carnosine is significantly depleted and 5-caffeoylquinic acid (5-CQA) levels rise sharply around Aβ deposits. These observations highlight the potential of carnosine as a sensitive molecular probe for clinical magnetic resonance imaging diagnosis and the potential of 5-CQA as an efficient therapeutic strategy for Aβ clearance in the early AD stage. Overall, our findings demonstrate the effectiveness of our STC-DESI method and shed light on the potential roles of these molecules in AD pathology, specifically in cellular endocytosis, gray matter network disruption, and paravascular Aβ clearance.

Study on the white frost formation mechanism during storage of Phyllanthus emblica Linn. fruit based on component analysis and spatial metabolomics

The Phyllanthus emblica Linn. fruit (PEF) is a well-known medicinal and food homologous item in tropical Southeast Asian. During the drying and storing processes, some PEF will grow white frost on its surface, which is typically taken as a sign of greater quality. However, the material basis and formation mechanism of white frost on PEF surfaces are currently unclear, and there is no sufficient evidence to support the correlation between white frost on PEF surfaces and their quality. In this paper, high-performance liquid chromatography (HPLC) was used to study the differences in active ingredient content of PEF medicinal materials with and without frost. The microstructure and elemental composition of white frost were studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The Fourier transform infrared spectroscopy (FT-IR) was used to analysis the main functional groups in white frost. The ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) combined with UNIFI database, EDS and FT-IR results, and reference materials were used to identify the chemical composition of white frost. The exocarp of PEF before and after drying and storage was analyzed by spatial metabolomics using desorption electrospray ionization (DESI) mass spectrometry imaging system to reveal the formation mechanism of white frost on the surface of PEF. The results found that the PEF with frost have higher levels of active ingredients than those without frost. EDS and FT-IR results show that white frost is mainly composed of C, O, K elements, and contains a large number of phenolic hydroxyl, carboxyl etc. UPLC-Q-TOF-MS/MS results found that the main components of white frost were organic acids, fatty acids, and tannins, including quality markers such as gallic acid and ellagic acid etc. Spatial metabolomics research found that the white frost formation mechanism mainly involved in the ascorbate and aldarate metabolism, cutin, suberin and wax biosynthesis, citrate cycle (TCA cycle) and biosynthesis of unsaturated fatty acid. This study reveals the material basis, formation mechanism, and relationship between the surface white frost of PEF and the quality of medicinal materials, providing valuable information for the quality evaluation of PEF.

Biomarker Identification in Liver Cancers Using Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) Imaging: An Approach for Spatially Resolved Metabolomics.

Liver cancers are characterized by interindividual and intratumoral heterogeneity, which makes early diagnosis and the development of therapies challenging. Desorption electrospray ionization mass spectrometry (DESI-MS) imaging is a potent and sensitive MS ionization technique for direct, unaltered 2D and 3D imaging of metabolites in complex biological samples. Indeed, DESI gently desorbs and ionizes analyte molecules from the sample surface using an electrospray source of highly charged aqueous spray droplets in ambient conditions. DESI-MS imaging of biological samples allows untargeted analysis and characterization of metabolites in liver cancers to identify new biomarkers of malignancy. In this chapter, we described a detailed protocol using liver cancer samples collected and stored for histopathology examination, either as frozen or as formalin-fixed, paraffin-embedded specimens. Such hepatocellular carcinoma samples can be subjected to DESI-MS analyses, illustrating the capacity of spatially resolved metabolomics to distinguish malignant lesions from adjacent normal liver tissue.

Radioinduced Modulatory Response of Lipid Profiles of Wistar Rats Brain Monitored by DESI-MS Imaging

The ionizing radiation used in radiotherapy can break down deoxyribonucleic acid bonds, generate reactive oxygen and nitrogen species, alter intracellular proteins, and induce changes in the lipidome. This study delves into examining lipid classes and their spatial distribution in the brains of Wistar rats exposed to ionizing radiation. Healthy male isogenic Wistar rats (n = 15) were divided into a control group (CG, n = 3) and an irradiated group (IRG, n = 12). The individuals of the IRG group were subjected to total body irradiation (TBI) using a Co-60 source and a radiation dose of 5 Gy. The IRG group was subdivided into four subgroups corresponding to 168, 96, 48, and 24 h before sacrifice. The brains were sliced into the sagittal direction, and the slices were analyzed using the desorption electrospray ionization mass spectrometry imaging (DESI-MSI) approach. The mass spectrometry results and information from the Metabolite and Chemical Entity Database (METLINTM) and Lipid Metabolites and Pathways Strategy (LIPID MAPS) databases enabled the identification of lipids belonging to distinct classes. The DESI-MS images revealed distinctive spatial distributions of these lipids and the modulatory response induced by the radiation over time.

Noninvasive Detection of Skin Cancer by Imprint Desorption Electrospray Ionization Mass Spectrometry Imaging.

We report a technique for the noninvasive detection of skin cancer by imprint desorption electrospray ionization mass spectrometry imaging (DESI-MSI) using a transfer agent that is pressed against the tissue of interest. By noninvasively pressing a tape strip against human skin, metabolites, fatty acids, and lipids on the skin surface are transferred to the tape with little spatial distortion. Running DESI-MSI on the tape strip provides chemical images of the molecules on the skin surface, which are valuable for distinguishing cancer from healthy skin. Chemical components of the tissue imprint on the tape strip and the original basal cell carcinoma (BCC) section from the mass spectra show high consistency. By comparing MS images (about 150-μm resolution) of same molecules from the tape strip and from the BCC section, we confirm that chemical patterns are successfully transferred to the tape stripe. We also used the technique to distinguish cherry angiomas from normal human skin by comparing the molecular patterns from a tape strip. These results demonstrate the potential of the imprint DESI-MSI technique for the noninvasive detection of skin cancers as well as other skin diseases before and during clinical surgery.

The visualization of the spatial distribution of Cocculus orbiculatus based on air flow-assisted desorption electrospray ionization mass spectrometry imaging

Cocculus orbiculatus (C. orbiculatus), the root of plants belonging to the Menispermaceae family, has been extensively used to treat various diseases, including malaria and rheumatism. The main chemicals in these plants are alkaloids; however, the spatial distribution of these compounds within the plant roots remains undefined. This study aimed to visualize the spatial distribution of C. orbiculatus using air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI). In total, the spatial distribution of four aporphine alkaloids, five benzyltetrahydroisoquinoline alkaloids, six bisbenzylisoquinoline alkaloids, and one morphinane alkaloid in the cork layer, xylem, and ray of the root of C. orbiculatus was observed; the distribution characteristics of the different compounds in C. orbiculatus were significantly different. This study provides a visualized spatial distribution analysis method for the characterization of metabolites in the root tissue of C. orbiculatus and also provides valuable information for the specificity of the root of C. orbiculatus, which is beneficial for understanding its chemical separation, biosynthesis, and pharmacological activities.

Investigation of metabolite alterations in thekidneys of methionine-choline-deficient mouse by mass spectrometry imaging.

Methionine and choline both are essential nutrients which are needed for methyl group metabolism. Amethionine-choline-deficient (MCD) diet leads to pathological changes in the kidney. The mechanism of theMCD diet is complex, and fundamental research is still required to provide a better understanding of the driving forces behind it. We evaluated the regional effects of the MCD diet on the metabolites of mouse kidney tissue using desorption electrospray ionization mass spectrometry imaging technology. A total of 20, 17, and 13 metabolites were significantly changed in the cortex, outer medulla, and inner medulla, respectively, of the mouse kidney tissue after the administration of theMCD diet. Among the discriminating metabolites, only three metabolites (guanidoacetic acid, serine, and nicotinamide riboside) were significantly increased, and all the other metabolites showed asignificant decrease. The results showed that there were significant region-specific changes in the serine metabolism, carnitine metabolism, choline metabolism, and arginine metabolism. This study presents unique regional metabolic data, providing a more comprehensive understanding of the molecular characteristics of theMCD diet in the kidney.