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1.
Cell ; 185(12): 2148-2163.e27, 2022 06 09.
Artículo en Inglés | MEDLINE | ID: mdl-35584702

RESUMEN

Zinc (Zn) is an essential micronutrient and cofactor for up to 10% of proteins in living organisms. During Zn limitation, specialized enzymes called metallochaperones are predicted to allocate Zn to specific metalloproteins. This function has been putatively assigned to G3E GTPase COG0523 proteins, yet no Zn metallochaperone has been experimentally identified in any organism. Here, we functionally characterize a family of COG0523 proteins that is conserved across vertebrates. We identify Zn metalloprotease methionine aminopeptidase 1 (METAP1) as a COG0523 client, leading to the redesignation of this group of COG0523 proteins as the Zn-regulated GTPase metalloprotein activator (ZNG1) family. Using biochemical, structural, genetic, and pharmacological approaches across evolutionarily divergent models, including zebrafish and mice, we demonstrate a critical role for ZNG1 proteins in regulating cellular Zn homeostasis. Collectively, these data reveal the existence of a family of Zn metallochaperones and assign ZNG1 an important role for intracellular Zn trafficking.


Asunto(s)
Metaloendopeptidasas/metabolismo , Zinc , Animales , GTP Fosfohidrolasas/metabolismo , Homeostasis , Metalochaperonas/metabolismo , Metaloproteínas/genética , Ratones , Pez Cebra/metabolismo , Zinc/metabolismo
2.
Nature ; 623(7989): 1009-1016, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37968387

RESUMEN

Iron is indispensable for almost all forms of life but toxic at elevated levels1-4. To survive within their hosts, bacterial pathogens have evolved iron uptake, storage and detoxification strategies to maintain iron homeostasis1,5,6. Recent studies showed that three Gram-negative environmental anaerobes produce iron-containing ferrosome granules7,8. However, it remains unclear whether ferrosomes are generated exclusively by Gram-negative bacteria. The Gram-positive bacterium Clostridioides difficile is the leading cause of nosocomial and antibiotic-associated infections in the USA9. Here we report that C. difficile undergoes an intracellular iron biomineralization process and stores iron in membrane-bound ferrosome organelles containing non-crystalline iron phosphate biominerals. We found that a membrane protein (FezA) and a P1B6-ATPase transporter (FezB), repressed by both iron and the ferric uptake regulator Fur, are required for ferrosome formation and play an important role in iron homeostasis during transition from iron deficiency to excess. Additionally, ferrosomes are often localized adjacent to cellular membranes as shown by cryo-electron tomography. Furthermore, using two mouse models of C. difficile infection, we demonstrated that the ferrosome system is activated in the inflamed gut to combat calprotectin-mediated iron sequestration and is important for bacterial colonization and survival during C. difficile infection.


Asunto(s)
Clostridioides difficile , Infecciones por Clostridium , Compuestos Férricos , Interacciones Microbiota-Huesped , Hierro , Orgánulos , Animales , Ratones , Clostridioides difficile/crecimiento & desarrollo , Clostridioides difficile/inmunología , Clostridioides difficile/metabolismo , Infecciones por Clostridium/inmunología , Infecciones por Clostridium/metabolismo , Infecciones por Clostridium/microbiología , Hierro/metabolismo , Orgánulos/metabolismo , Homeostasis , Compuestos Férricos/metabolismo , Proteínas Bacterianas/metabolismo , Membrana Celular/metabolismo , Microscopía por Crioelectrón , Tomografía con Microscopio Electrónico , Modelos Animales de Enfermedad , Complejo de Antígeno L1 de Leucocito/metabolismo , Viabilidad Microbiana , Inflamación/metabolismo , Inflamación/microbiología , Intestinos/metabolismo , Intestinos/microbiología
3.
Nat Methods ; 20(8): 1174-1178, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37468619

RESUMEN

Multiplexed antibody-based imaging enables the detailed characterization of molecular and cellular organization in tissues. Advances in the field now allow high-parameter data collection (>60 targets); however, considerable expertise and capital are needed to construct the antibody panels employed by these methods. Organ mapping antibody panels are community-validated resources that save time and money, increase reproducibility, accelerate discovery and support the construction of a Human Reference Atlas.


Asunto(s)
Anticuerpos , Recursos Comunitarios , Humanos , Reproducibilidad de los Resultados , Diagnóstico por Imagen
4.
Nat Methods ; 19(3): 284-295, 2022 03.
Artículo en Inglés | MEDLINE | ID: mdl-34811556

RESUMEN

Tissues and organs are composed of distinct cell types that must operate in concert to perform physiological functions. Efforts to create high-dimensional biomarker catalogs of these cells have been largely based on single-cell sequencing approaches, which lack the spatial context required to understand critical cellular communication and correlated structural organization. To probe in situ biology with sufficient depth, several multiplexed protein imaging methods have been recently developed. Though these technologies differ in strategy and mode of immunolabeling and detection tags, they commonly utilize antibodies directed against protein biomarkers to provide detailed spatial and functional maps of complex tissues. As these promising antibody-based multiplexing approaches become more widely adopted, new frameworks and considerations are critical for training future users, generating molecular tools, validating antibody panels, and harmonizing datasets. In this Perspective, we provide essential resources, key considerations for obtaining robust and reproducible imaging data, and specialized knowledge from domain experts and technology developers.


Asunto(s)
Anticuerpos , Comunicación Celular , Diagnóstico por Imagen
5.
Am J Physiol Renal Physiol ; 327(1): F91-F102, 2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38721662

RESUMEN

The lack of standardization in antibody validation remains a major contributor to irreproducibility of human research. To address this, we have applied a standardized approach to validate a panel of antibodies to identify 18 major cell types and 5 extracellular matrix compartments in the human kidney by immunofluorescence (IF) microscopy. We have used these to generate an organ mapping antibody panel for two-dimensional (2-D) and three-dimensional (3-D) cyclical IF (CyCIF) to provide a more detailed method for evaluating tissue segmentation and volumes using a larger panel of markers than would normally be possible using standard fluorescence microscopy. CyCIF also makes it possible to perform multiplexed IF microscopy of whole slide images, which is a distinct advantage over other multiplexed imaging technologies that are applicable to limited fields of view. This enables a broader view of cell distributions across larger anatomical regions, allowing a better chance to capture localized regions of dysfunction in diseased tissues. These methods are broadly accessible to any laboratory with a fluorescence microscope, enabling spatial cellular phenotyping in normal and disease states. We also provide a detailed solution for image alignment between CyCIF cycles that can be used by investigators to perform these studies without programming experience using open-sourced software. This ability to perform multiplexed imaging without specialized instrumentation or computational skills opens the door to integration with more highly dimensional molecular imaging modalities such as spatial transcriptomics and imaging mass spectrometry, enabling the discovery of molecular markers of specific cell types, and how these are altered in disease.NEW & NOTEWORTHY We describe here validation criteria used to define on organ mapping panel of antibodies that can be used to define 18 cell types and five extracellular matrix compartments using cyclical immunofluorescence (CyCIF) microscopy. As CyCIF does not require specialized instrumentation, and image registration required to assemble CyCIF images can be performed by any laboratory without specialized computational skills, this technology is accessible to any laboratory with access to a fluorescence microscope and digital scanner.


Asunto(s)
Anticuerpos , Riñón , Microscopía Fluorescente , Humanos , Microscopía Fluorescente/métodos , Riñón/inmunología , Riñón/metabolismo , Anticuerpos/inmunología , Técnica del Anticuerpo Fluorescente/métodos , Reproducibilidad de los Resultados , Matriz Extracelular/metabolismo , Matriz Extracelular/inmunología , Imagenología Tridimensional/métodos
6.
Anal Chem ; 96(13): 5065-5070, 2024 04 02.
Artículo en Inglés | MEDLINE | ID: mdl-38517028

RESUMEN

In this work, we demonstrate rapid, high spatial, and high spectral resolution imaging of intact proteins by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) on a hybrid quadrupole-reflectron time-of-flight (qTOF) mass spectrometer equipped with trapped ion mobility spectrometry (TIMS). Historically, untargeted MALDI IMS of proteins has been performed on TOF mass spectrometers. While advances in TOF instrumentation have enabled rapid, high spatial resolution IMS of intact proteins, TOF mass spectrometers generate relatively low-resolution mass spectra with limited mass accuracy. Conversely, the implementation of MALDI sources on high-resolving power Fourier transform (FT) mass spectrometers has allowed IMS experiments to be conducted with high spectral resolution with the caveat of increasingly long data acquisition times. As illustrated here, qTOF mass spectrometers enable protein imaging with the combined advantages of TOF and FT mass spectrometers. Protein isotope distributions were resolved for both a protein standard mixture and proteins detected from a whole-body mouse pup tissue section. Rapid (∼10 pixels/s) 10 µm lateral spatial resolution IMS was performed on a rat brain tissue section while maintaining isotopic spectral resolution. Lastly, proof-of-concept MALDI-TIMS data was acquired from a protein mixture to demonstrate the ability to differentiate charge states by ion mobility. These experiments highlight the advantages of qTOF and timsTOF platforms for resolving and interpreting complex protein spectra generated from tissue by IMS.


Asunto(s)
Diagnóstico por Imagen , Proteínas , Ratas , Ratones , Animales , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Análisis de Fourier
7.
Anal Chem ; 96(42): 16861-16870, 2024 Oct 22.
Artículo en Inglés | MEDLINE | ID: mdl-39392310

RESUMEN

Thermal denaturation (TD), known as antigen retrieval, heats tissue samples in a buffered solution to expose protein epitopes. Thermal denaturation of formalin-fixed paraffin-embedded samples enhances on-tissue tryptic digestion, increasing peptide detection using matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS). We investigated the tissue-dependent effects of TD on peptide MALDI IMS and liquid chromatography-tandem mass spectrometry signal in unfixed, frozen human colon, ovary, and pancreas tissue. In a triplicate experiment using time-of-flight, orbitrap, and Fourier-transform ion cyclotron resonance mass spectrometry platforms, we found that TD had a tissue-dependent effect on peptide signal, resulting in a (22.5%) improvement in peptide detection from the colon, a (73.3%) improvement in ovary tissue, and a (96.6%) improvement in pancreas tissue. Biochemical analysis of identified peptides shows that TD facilitates identification of hydrophobic peptides.


Asunto(s)
Páncreas , Péptidos , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Humanos , Péptidos/química , Péptidos/análisis , Páncreas/química , Femenino , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Colon/química , Ovario/química , Calor , Espectrometría de Masas en Tándem/métodos , Congelación
8.
Mol Cell Proteomics ; 21(7): 100254, 2022 07.
Artículo en Inglés | MEDLINE | ID: mdl-35654359

RESUMEN

All human diseases involve proteins, yet our current tools to characterize and quantify them are limited. To better elucidate proteins across space, time, and molecular composition, we provide a >10 years of projection for technologies to meet the challenges that protein biology presents. With a broad perspective, we discuss grand opportunities to transition the science of proteomics into a more propulsive enterprise. Extrapolating recent trends, we describe a next generation of approaches to define, quantify, and visualize the multiple dimensions of the proteome, thereby transforming our understanding and interactions with human disease in the coming decade.


Asunto(s)
Proteoma , Proteómica , Humanos , Proteoma/metabolismo , Proteómica/métodos
9.
J Proteome Res ; 22(5): 1394-1405, 2023 05 05.
Artículo en Inglés | MEDLINE | ID: mdl-35849531

RESUMEN

Spatially targeted proteomics analyzes the proteome of specific cell types and functional regions within tissue. While spatial context is often essential to understanding biological processes, interpreting sub-region-specific protein profiles can pose a challenge due to the high-dimensional nature of the data. Here, we develop a multivariate approach for rapid exploration of differential protein profiles acquired from distinct tissue regions and apply it to analyze a published spatially targeted proteomics data set collected from Staphylococcus aureus-infected murine kidney, 4 and 10 days postinfection. The data analysis process rapidly filters high-dimensional proteomic data to reveal relevant differentiating species among hundreds to thousands of measured molecules. We employ principal component analysis (PCA) for dimensionality reduction of protein profiles measured by microliquid extraction surface analysis mass spectrometry. Subsequently, k-means clustering of the PCA-processed data groups samples by chemical similarity. Cluster center interpretation revealed a subset of proteins that differentiate between spatial regions of infection over two time points. These proteins appear involved in tricarboxylic acid metabolomic pathways, calcium-dependent processes, and cytoskeletal organization. Gene ontology analysis further uncovered relationships to tissue damage/repair and calcium-related defense mechanisms. Applying our analysis in infectious disease highlighted differential proteomic changes across abscess regions over time, reflecting the dynamic nature of host-pathogen interactions.


Asunto(s)
Calcio , Proteómica , Animales , Ratones , Proteómica/métodos , Biología Computacional/métodos , Análisis Multivariante , Proteoma/metabolismo
10.
Anal Chem ; 95(2): 1176-1183, 2023 01 17.
Artículo en Inglés | MEDLINE | ID: mdl-36574465

RESUMEN

Gangliosides are acidic glycosphingolipids, containing ceramide moieties and oligosaccharide chains with one or more sialic acid residue(s) and are highly diverse isomeric structures with distinct biological roles. Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) enables the untargeted spatial analysis of gangliosides, among other biomolecules, directly from tissue sections. Integrating trapped ion mobility spectrometry with MALDI IMS allows for the analysis of isomeric lipid structures in situ. Here, we demonstrate the gas-phase separation and identification of disialoganglioside isomers GD1a and GD1b that differ in the position of a sialic acid residue, in multiple samples, including a standard mixture of both isomers, a biological extract, and directly from thin tissue sections. The unique spatial distributions of GD1a/b (d36:1) and GD1a/b (d38:1) isomers were determined in rat hippocampus and spinal cord tissue sections, demonstrating the ability to structurally characterize and spatially map gangliosides based on both the carbohydrate chain and ceramide moieties.


Asunto(s)
Gangliósidos , Ácido N-Acetilneuramínico , Ratones , Ratas , Animales , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Gangliósidos/análisis , Encéfalo , Ceramidas
11.
Trends Analyt Chem ; 1692023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-38045023

RESUMEN

Imaging mass spectrometry (IMS) allows for the untargeted mapping of biomolecules directly from tissue sections. This technology is increasingly integrated into biomedical and clinical research environments to supplement traditional microscopy and provide molecular context for tissue imaging. IMS has widespread clinical applicability in the fields of oncology, dermatology, microbiology, and others. This review summarizes the two most widely employed IMS technologies, matrix-assisted laser desorption/ionization (MALDI) and desorption electrospray ionization (DESI), and covers technological advancements, including efforts to increase spatial resolution, specificity, and throughput. We also highlight recent biomedical applications of IMS, primarily focusing on disease diagnosis, classification, and subtyping.

12.
Adv Exp Med Biol ; 1415: 3-7, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37440006

RESUMEN

Pathologies of the retina are clinically visualized in vivo with OCT and ex vivo with immunohistochemistry. Although both techniques provide valuable information on prognosis and disease state, a comprehensive method for fully elucidating molecular constituents present in locations of interest is desirable. The purpose of this work was to use multimodal imaging technologies to localize the vast number of molecular species observed with matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) in aged and diseased retinal tissues. Herein, MALDI IMS was utilized to observe molecular species that reside in photoreceptor cells and also a basal laminar deposit from two human donor eyes. The molecular species observed to accumulate in these discrete regions can be further identified and studied to attempt to gain a greater understanding of biological processes occurring in debilitating eye diseases such as age-related macular degeneration (AMD).


Asunto(s)
Degeneración Macular , Humanos , Anciano , Degeneración Macular/diagnóstico por imagen , Degeneración Macular/patología , Retina/patología , Membrana Basal , Células Fotorreceptoras/patología , Espectrometría de Masas
13.
Kidney Int ; 101(1): 137-143, 2022 01.
Artículo en Inglés | MEDLINE | ID: mdl-34619231

RESUMEN

The human kidney is composed of many cell types that vary in their abundance and distribution from normal to diseased organ. As these cell types perform unique and essential functions, it is important to confidently label each within a single tissue to accurately assess tissue architecture and microenvironments. Towards this goal, we demonstrate the use of co-detection by indexing (CODEX) multiplexed immunofluorescence for visualizing 23 antigens within the human kidney. Using CODEX, many of the major cell types and substructures, such as collecting ducts, glomeruli, and thick ascending limb, were visualized within a single tissue section. Of these antibodies, 19 were conjugated in-house, demonstrating the flexibility and utility of this approach for studying the human kidney using custom and commercially available antibodies. We performed a pilot study that compared both fresh frozen and formalin-fixed paraffin-embedded healthy non-neoplastic and diabetic nephropathy kidney tissues. The largest cellular differences between the two groups was observed in cells labeled with aquaporin 1, cytokeratin 7, and α-smooth muscle actin. Thus, our data show the power of CODEX multiplexed immunofluorescence for surveying the cellular diversity of the human kidney and the potential for applications within pathology, histology, and building anatomical atlases.


Asunto(s)
Anticuerpos , Riñón , Técnica del Anticuerpo Fluorescente , Humanos , Riñón/patología , Proyectos Piloto , Coloración y Etiquetado
14.
Anal Chem ; 94(14): 5504-5513, 2022 04 12.
Artículo en Inglés | MEDLINE | ID: mdl-35344335

RESUMEN

Because of their diverse functionalities in cells, lipids are of primary importance when characterizing molecular profiles of physiological and disease states. Imaging mass spectrometry (IMS) provides the spatial distributions of lipid populations in tissues. Referenced Kendrick mass defect (RKMD) analysis is an effective mass spectrometry (MS) data analysis tool for classification and annotation of lipids. Herein, we extend the capabilities of RKMD analysis and demonstrate an integrated method for lipid annotation and chemical structure-based filtering for IMS datasets. Annotation of lipid features with lipid molecular class, radyl carbon chain length, and degree of unsaturation allows image reconstruction and visualization based on each structural characteristic. We show a proof-of-concept application of the method to a computationally generated IMS dataset and validate that the RKMD method is highly specific for lipid components in the presence of confounding background ions. Moreover, we demonstrate an application of the RKMD-based annotation and filtering to matrix-assisted laser desorption/ionization (MALDI) IMS lipidomic data from human kidney tissue analysis.


Asunto(s)
Cefotaxima , Lipidómica , Humanos , Iones , Lípidos/análisis , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos
15.
Anal Chem ; 94(7): 3165-3172, 2022 02 22.
Artículo en Inglés | MEDLINE | ID: mdl-35138834

RESUMEN

Bone and bone marrow are vital to mammalian structure, movement, and immunity. These tissues are also commonly subjected to molecular alterations giving rise to debilitating diseases like rheumatoid arthritis and osteomyelitis. Technologies such as matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) facilitate the discovery of spatially resolved chemical information in biological tissue samples to help elucidate the complex molecular processes underlying pathology. Traditionally, preparation of osseous tissue for MALDI IMS has been difficult due to its mineralized composition and heterogeneous morphology, and compensation for these challenges with decalcification and fixation protocols can remove or delocalize molecular species. Here, sample preparation methods were advanced to enable multimodal MALDI IMS of undecalcified, fresh-frozen murine femurs, allowing the distribution of endogenous lipids to be linked to tissue structures and cell types. Adhesive-bound bone sections were mounted onto conductive glass slides with microscopy-compatible glue and freeze-dried to minimize artificial bone marrow damage. High spatial resolution (10 µm) MALDI IMS was employed to characterize lipid distributions, and use of complementary microscopy modalities aided tissue and cell assignments. For example, various phosphatidylcholines localize to the bone marrow, adipose tissue, marrow adipose tissue, and muscle. Further, sphingomyelin(42:1) was abundant in megakaryocytes, whereas sphingomyelin(42:2) was diminished in this cell type. These data reflect the vast molecular and cellular heterogeneity indicative of the bone marrow and the soft tissue surrounding the femur. Multimodal MALDI IMS has the potential to advance bone-related biomedical research by offering deep molecular coverage with spatial relevance in a preserved native bone microenvironment.


Asunto(s)
Huesos , Microscopía , Animales , Ratones , Músculos , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Esfingomielinas
16.
Proc Natl Acad Sci U S A ; 116(44): 21980-21982, 2019 10 29.
Artículo en Inglés | MEDLINE | ID: mdl-31611408

RESUMEN

Siderophores, iron-scavenging small molecules, are fundamental to bacterial nutrient metal acquisition and enable pathogens to overcome challenges imposed by nutritional immunity. Multimodal imaging mass spectrometry allows visualization of host-pathogen iron competition, by mapping siderophores within infected tissue. We have observed heterogeneous distributions of Staphylococcus aureus siderophores across infectious foci, challenging the paradigm that the vertebrate host is a uniformly iron-depleted environment to invading microbes.


Asunto(s)
Sideróforos/análisis , Staphylococcus aureus/patogenicidad , Absceso/microbiología , Animales , Citratos/análisis , Interacciones Huésped-Patógeno , Hierro/metabolismo , Ratones , Ornitina/análogos & derivados , Ornitina/análisis , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Infecciones Estafilocócicas/microbiología , Infecciones Estafilocócicas/patología
17.
Gastroenterology ; 159(2): 453-466.e1, 2020 08.
Artículo en Inglés | MEDLINE | ID: mdl-32417404

RESUMEN

Single cells are the building blocks of tissue systems that determine organ phenotypes, behaviors, and functions. Understanding the differences between cell types and their activities might provide us with insights into normal tissue physiology, development of disease, and new therapeutic strategies. Although -omic level single-cell technologies are a relatively recent development that have been used only in research settings, these approaches might eventually be used in the clinic. We review the prospects of applying single-cell genome, transcriptome, epigenome, proteome, and metabolome analyses to gastroenterology and hepatology research. Combining data from multi-omic platforms coupled to rapid technological development could lead to new diagnostic, prognostic, and therapeutic approaches.


Asunto(s)
Investigación Biomédica/métodos , Enfermedades Gastrointestinales/diagnóstico , Tracto Gastrointestinal/fisiología , Análisis de la Célula Individual , Enfermedades Gastrointestinales/etiología , Enfermedades Gastrointestinales/fisiopatología , Enfermedades Gastrointestinales/terapia , Tracto Gastrointestinal/citología , Perfilación de la Expresión Génica/métodos , Genómica/métodos , Humanos , Metabolómica/métodos , Proteómica/métodos
18.
Anal Chem ; 93(36): 12243-12249, 2021 09 14.
Artículo en Inglés | MEDLINE | ID: mdl-34449196

RESUMEN

We have developed a pre-coated substrate for matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) that enables high spatial resolution mapping of both phospholipids and neutral lipid classes in positive ion mode as metal cation adducts. The MALDI substrates are constructed by depositing a layer of α-cyano-4-hydroxycinnamic acid (CHCA) and potassium salts onto silicon nanopost arrays (NAPA) prior to tissue mounting. The matrix/salt pre-coated NAPA substrate significantly enhances all detected lipid signals allowing lipids to be detected at lower laser energies than bare NAPA. The improved sensitivity at lower laser energy enabled ion images to be generated at 10 µm spatial resolution from rat retinal tissue. Optimization of matrix pre-coated NAPA consisted of testing lithium, sodium, and potassium salts along with various matrices to investigate the increased sensitivity toward lipids for MALDI IMS experiments. It was determined that pre-coating NAPA with CHCA and potassium salts before thaw-mounting of tissue resulted in a signal intensity increase of at least 5.8 ± 0.1-fold for phospholipids and 2.0 ± 0.1-fold for neutral lipids compared to bare NAPA. Pre-coating NAPA with matrix and salt also reduced the necessary laser power to achieve desorption/ionization by ∼35%. This reduced the effective diameter of the ablation area from 13 ± 2 µm down to 8 ± 1 µm, enabling high spatial resolution MALDI IMS. Using pre-coated NAPA with CHCA and potassium salts offers a MALDI IMS substrate with broad molecular coverage of lipids in a single polarity that eliminates the need for extensive sample preparation after sectioning.


Asunto(s)
Citrato de Potasio , Silicio , Animales , Ácido Cítrico , Ácidos Cumáricos , Fosfolípidos , Potasio , Ratas , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción
19.
J Am Chem Soc ; 142(43): 18369-18377, 2020 10 28.
Artículo en Inglés | MEDLINE | ID: mdl-32709196

RESUMEN

Many microorganisms possess the capacity for producing multiple antibiotic secondary metabolites. In a few notable cases, combinations of secondary metabolites produced by the same organism are used in important combination therapies for treatment of drug-resistant bacterial infections. However, examples of conjoined roles of bioactive metabolites produced by the same organism remain uncommon. During our genetic functional analysis of oxidase-encoding genes in the everninomicin producer Micromonospora carbonacea var. aurantiaca, we discovered previously uncharacterized antibiotics everninomicin N and O, comprised of an everninomicin fragment conjugated to the macrolide rosamicin via a rare nitrone moiety. These metabolites were determined to be hydrolysis products of everninomicin P, a nitrone-linked conjugate likely the result of nonenzymatic condensation of the rosamicin aldehyde and the octasaccharide everninomicin F, possessing a hydroxylamino sugar moiety. Rosamicin binds the erythromycin macrolide binding site approximately 60 Å from the orthosomycin binding site of everninomicins. However, while individual ribosomal binding sites for each functional half of everninomicin P are too distant for bidentate binding, ligand displacement studies demonstrated that everninomicin P competes with rosamicin for ribosomal binding. Chemical protection studies and structural analysis of everninomicin P revealed that everninomicin P occupies both the macrolide- and orthosomycin-binding sites on the 70S ribosome. Moreover, resistance mutations within each binding site were overcome by the inhibition of the opposite functional antibiotic moiety binding site. These data together demonstrate a strategy for coupling orthogonal antibiotic pharmacophores, a surprising tolerance for substantial covalent modification of each antibiotic, and a potential beneficial strategy to combat antibiotic resistance.


Asunto(s)
Óxidos de Nitrógeno/química , Ribosomas/metabolismo , Aminoglicósidos/química , Aminoglicósidos/metabolismo , Sitios de Unión , Microscopía por Crioelectrón , Eritromicina/química , Eritromicina/metabolismo , Leucomicinas/química , Leucomicinas/metabolismo , Micromonospora/genética , Familia de Multigenes , Óxidos de Nitrógeno/metabolismo
20.
Anal Chem ; 92(19): 13092-13100, 2020 10 06.
Artículo en Inglés | MEDLINE | ID: mdl-32845133

RESUMEN

In the analysis of biological tissue by imaging mass spectrometry (IMS), the limit of detection and dynamic range are of paramount importance in obtaining experimental results that provide insight into underlying biological processes. Many important biomolecules are present in the tissue milieu in low concentrations and in complex mixtures with other compounds of widely ranging abundances, challenging the limits of analytical technologies. In many IMS experiments, the ion signal can be dominated by a few highly abundant ion species. On trap-based instrument platforms that accumulate ions prior to mass analysis, these high abundance ions can diminish the detection and dynamic range of lower abundance ions. Herein, we describe two strategies for combating these challenges during IMS experiments on a hybrid QhFT-ICR MS. In one iteration, the mass resolving capabilities of a quadrupole mass filter are used to selectively enrich ions of interest via a technique previously termed continuous accumulation of selected ions. Second, we have introduced a supplemental dipolar AC waveform to the quadrupole mass filter of a commercial QhFT-ICR mass spectrometer to perform selected ion ejection prior to the ion accumulation region. This setup allows the selective ejection of the most abundant ion species prior to ion accumulation, thereby greatly improving the molecular depth with which IMS can probe tissue samples. The gain in sensitivity of both of these approaches roughly scales with the number of accumulated laser shots up to the charge capacity of the ion accumulation cell. The efficiencies of these two strategies are described here by performing lipid imaging mass spectrometry analyses of a rat brain.


Asunto(s)
Encéfalo/metabolismo , Lípidos/análisis , Animales , Gases/química , Iones/química , Espectrometría de Masas , Ratas
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