Mass Spectrometry Reviews最新文献

Secondary electrospray ionization (SESI) and extractive electrospray ionization (EESI), as derivative technologies of electrospray ionization (ESI), have empowered the real-time analysis of trace compounds residing in gases and aerosols. Over the past three decades, SESI and EESI have demonstrated remarkable potential in a wide spectrum of applications, spanning disease diagnosis, drug detection, food safety, and environmental surveillance. Concurrently, the strides made in deciphering the ionization mechanisms of SESI and EESI have spurred the creation of diverse ion source configurations that are characterized by enhanced sensitivity and diminished background noise. This comprehensive review encapsulates the ionization mechanisms inherent in SESI and EESI processes, with particular emphasis on the impact of analyte characteristics (such as proton affinity, dipole moment, polarizability, and solubility) and ion source operational parameters (encompassing temperature, humidity, voltage, flow rate and electrospray composition) on ionization efficiency. Additionally, it delves into the progression of SESI and EESI sources, highlights recent breakthroughs, and probes into future trajectories, furnishing novel perspectives for the development of both technologies and the associated instruments.

Ionization and fragmentation are at the core of mass spectrometry. But they are not necessarily separated in space, as in-source fragmentation can also occur. Here, we survey the literature published since our 2005 review on the internal energy and fragmentation in electrospray ionization sources. We present new thermometer molecules to diagnose and quantify source heating, provide tables of recommended threshold (E₀) and appearance energies (E_app) for the survival yield method, and attempt to compare the softness of a variety of ambient pressure ionization sources. The droplet size distribution and desolvation dynamics play a major role: lower average internal energies are obtained when the ions remain protected by a solvation shell and spend less time nakedly exposed to activating conditions in the transfer interface. Methods based on small droplet formation without charging can thus be softer than electrospray. New dielectric barrier discharge sources can gas-phase ionize small molecules while conferring barely more internal energy than electrospray ionization. However, the tuning of the entire source interface often has an even greater influence on ion internal energies and fragmentation than on the ionization process itself. We hope that this review will facilitate further research to control and standardize in-source ion activation conditions, and to ensure the transferability of data and research results in mass spectrometry.

Monosaccharides play a central role in metabolic networks and in the biosynthesis of glycomolecules, which perform essential functions across all domains of life. Thus, identifying and quantifying these building blocks is crucial in both research and industry. Routine methods have been established to facilitate the analysis of common monosaccharides. However, despite the presence of common metabolites, most organisms utilize distinct sets of monosaccharides and derivatives. These molecules therefore display a large diversity, potentially numbering in the hundreds or thousands, with many still unknown. This complexity presents significant challenges in the study of glycomolecules, particularly in microbes, including pathogens and those with the potential to serve as novel model organisms. This review discusses mass spectrometric techniques for the isomer-sensitive analysis of monosaccharides, their derivatives, and activated forms. Although mass spectrometry allows for untargeted analysis and sensitive detection in complex matrices, the presence of stereoisomers and extensive modifications necessitates the integration of advanced chromatographic, electrophoretic, ion mobility, or ion spectroscopic methods. Furthermore, stable-isotope incorporation studies are critical in elucidating biosynthetic routes in novel organisms.

Cancer treatment is far from optimal also because current classification systems do not reflect the complex molecular status of the tumor and its phenotype in sufficient detail. To construct molecular tumor classifiers, omics tools provide complex molecular data reflecting many aspects from genotype to phenotype. However, the true molecular effectors in the cells are proteins which often serve as potent cancer biomarkers and therapy targets. This review summarizes the method aspects that allowed the data-independent acquisition (DIA) mass spectrometry (MS) to outperform the traditional, data-dependent acquisition (DDA) approach in recent years. DIA-MS studies have already recapitulated molecular classification of colorectal and breast cancer, provided data improving molecular classification of prostate and other cancers, and led to validated diagnostic, prognostic, predictive biomarkers and therapy targets for common solid tumors. Tissue-specific spectral libraries are important for a deep characterization of tissue proteomes. Further perspectives of current cancer proteomics lie in the fields of single-cell and spatial proteomics and their integration with clinical data. The importance of functional and clinical validation is highlighted to allow stratified and/or personalized targeted therapy.

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has rapidly advanced in biomedical research, enabling label-free, untargeted spatial detection of metabolites, lipids, proteins, and glycans in tissue sections. However, challenges such as low ionization efficiency and chemical instability limit the detection of certain molecules. To address these issues, on-tissue chemical derivatization (OTCD) has been widely applied as an effective strategy to enhance imaging capabilities. This review systematically summarizes the development of derivatization reagents targeting different reactive functional groups and their applications in MALDI-MSI, including strategies for the derivatization of amines, carbonyls, carboxyls, double bonds, hydroxyls, thiols, and platinum-based drugs. Particular attention is given to how these derivatization reagents enhance the detection range and biological relevance by increasing molecular weight, improving ionization efficiency, and reducing background noise interference. Additionally, we explore the application of OTCD in various biological samples and discuss challenges related to experimental workflows, derivatization efficiency, and tissue integrity. This review provides important theoretical support for the advancement of MSI technology and highlights its broad potential applications in biomedical research.

Tannins are widespread specialized plant metabolites that contribute significantly to the polyphenol content of plant-based diets. Their effects on human and animal health vary depending on their structure, with potential benefits including antioxidative, antimicrobial, anthelmintic, and anticarcinogenic properties. Understanding tannin composition and quantity in plant products is essential, as their bioactivities are influenced by their functional groups. Mass spectrometry-based techniques excel in tannin analysis, offering both qualitative and quantitative insights. Combining ultrahigh-performance liquid chromatography with electrospray ionization and high-resolution and triple quadrupole mass analyzers is optimal for comprehensive tannin profiling. Such an approach enables precise analysis and helps predict tannin bioactivities. This review highlights the mass spectrometric analysis of proanthocyanidins and hydrolysable tannins, addressing ionization techniques, interpretation of multiply charged ions, characteristic fragmentations, and reaction monitoring. Applications related to tannin bioactivities are also briefly discussed, demonstrating the utility of mass spectrometry in tannin analysis in complex sample matrices.