Mass spectrometry最新文献

Light stabilizers are additives that are widely used to improve the lifespan and performance of polymer materials. To develop advanced polymer materials, analytical techniques investigate the degradation mechanisms and distribution of additives in polymers are crucial. Herein, two extraction-ionization methods were used: tapping-mode scanning probe electrospray ionization (t-SPESI) and liquid extraction surface analysis (LESA). The distribution and molecular structure of the photodegradation products were investigated using polyethylene films containing two types of oligomeric hindered amine light stabilizers (o-HALS). In addition, to study the relationship between light irradiation time and the relative amount of photodegradation products, we developed a method for preparing films with multiple photodegradation regions. Mass spectrometry imaging (MSI) using t-SPESI (t-SPESI-MSI) revealed that the signal intensities of HALS decreased with the time of light irradiation, and its degradation products progressively changed. Moreover, tandem mass spectrometry (MS/MS) using LESA (LESA-MS/MS) revealed that degradation products were generated by HALS fragmentation in the polymer film. By integrating these results, we propose multiple and stepwise reactions for the formation of the photodegradation products. Results indicate that the combined use of t-SPESI-MSI and LESA-MS/MS can directly analyze and understand the photodegradation mechanism of o-HALS in polymer materials.

Gold nanorods (AuNRs) possess anisotropic optical and electronic properties, primarily determined by their aspect ratio and surface ligands, which make them attractive for applications in sensing, catalysis, and nanomedicine. While these nanorods are typically stabilized using cetyltrimethylammonium bromide (CTAB) to ensure colloidal dispersion, the cytotoxicity and strong surface affinity of CTAB hinder further surface modification through ligand exchange. In this study, we employed matrix-free laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) to directly monitor the ligand exchange process on AuNRs. This technique enables the detection of intact CTAB, transient intermediates, and final thiol-bound ligands without requiring chemical derivatization. By correlating mass spectral data with ultraviolet-visible-near-infrared absorption and zeta potential measurements, we elucidate a stepwise ligand exchange mechanism in which CTAB is gradually displaced by a thiol-functionalized phosphorylcholine ligand, facilitated by electrostatic interaction with poly(styrene sulfonate). These findings highlight the utility of matrix-free LDI-TOF-MS as a powerful analytical tool for gaining mechanistic insights into ligand exchange reactions at the nanoscale, particularly in aqueous environments.

[This corrects the article DOI: 10.5702/massspectrometry.A0169.].

Congenital disorders of glycosylation (CDG) constitute a group of rare inherited metabolic disorders resulting from mutations in genes involved in the biosynthesis of glycan chains that are covalently attached to proteins or lipids. To date, nearly 200 genes have been identified as responsible for these disorders, with approximately half implicated in N-glycosylation defects. Diagnosis of CDG is primarily achieved through genetic analysis and the identification of glycan abnormalities, referred to as molecular phenotypes. With the increasing use of whole exome and genome sequencing in the investigation of diseases with unknown etiology, the number of cases suspected of CDG is increasing, highlighting the necessity for glycan analysis. Molecular phenotyping in CDG typically targets glycoproteins, with transferrin and apolipoprotein CIII being key representatives of N- and mucin-type O-glycosylation, respectively. Mass spectrometry (MS) provides rapid analysis and yields moderately detailed information, establishing it as a first-line molecular diagnostic tool that complements genetic analysis. Structural anomalies detected by MS can be classified into distinct patterns, which may indicate specific defects within the glycosylation pathway. In cases of CDG types that lack clear molecular phenotypes, characteristic metabolites can often be identified and quantified by MS, further aiding in the diagnostic process. Molecular diagnosis of CDG using MS can be performed with a standard mass spectrometer and a dried blood spot on filter paper, enabling its application in population-based mass screening.

In this study, we propose an effective summarization method for mass spectrometry imaging (MSI) data and demonstrate its efficacy. The MSI data used in this study were obtained from thoracic tissue sections of mice, including the thymus. The thymus is a multi-lobed organ composed of cortical and medullary areas, playing a crucial role in T-cell differentiation. By applying MSI to the thoracic region, including the thymus, this study aims to comprehensively visualize changes in molecular localization and metabolic patterns across thoracic organs. MSI data are highly information-rich, making effective summarization and organization challenging. Therefore, we explored a method to organize and visualize the data based on either spatial or m/z values. Specifically, we employed Uniform Manifold Approximation and Projection (UMAP) to project m/z data into 3-dimensional space, followed by k-means clustering to divide it into multiple clusters. This approach enables detailed and comprehensive representation of diverse features. The objective of this study is to identify molecular localizations and patterns that conventional methods may overlook. Furthermore, experimental results demonstrated that the pseudo-color images generated using UMAP highlighted specific m/z values that significantly influence image characteristics. When focusing on thoracic data, spatial segmentation resulted in clearer color differentiation; however, molecular localizations corresponding to blood vessels were not observed. This finding confirms that m/z segmentation is more effective than spatial segmentation in discovering new molecular localizations.

Isotope dilution mass spectrometry is a widely used method for measuring intracellular metabolite concentrations, relying on the ratio of peak areas between the target compound and its stable isotope-labeled internal standard. For metabolome analysis of microorganisms, comprehensive concentration measurements have been achieved through the preparation of stable isotope-labeled internal standard extracts (SILIS). Methods have been developed to prepare SILIS by extracting crude metabolites from fully ¹³C-labeled bacteria Escherichia coli and yeasts Saccharomyces cerevisiae and Pichia pastoris (Komagataella phaffii). For cost-effective preparation of SILIS, ideal characteristics of host yeasts include rapid cell growth, high biomass production, and significant metabolite accumulation. In this study, suitable yeast species for SILIS production were investigated from diverse candidates. Batch cultures of 15 yeast species from 12 genera were performed in synthetic defined medium, with cells harvested at different growth phases and metabolites extracted using the methanol/chloroform/water method. Metabolomic analysis by liquid chromatography-tandem mass spectrometry revealed the relative concentrations of 65 metabolites. The results demonstrated that S. cerevisiae and Kluyveromyces marxianus in the stationary phase were the most effective for SILIS production of central metabolic intermediates. SILIS production using S. cerevisiae and K. marxianus can be widely applied in standard laboratories because these species are safe, the media are commercially available, and the extraction methods are easily implementable.

Artificial intelligence (AI) has provided viable methods for retrieving, organizing, and analyzing mass spectrometry (MS) data in various applications. However, several challenges remain as this technique is still in its early, preliminary stages. Critical limitations include the need for more effective methods for identification, quantification, and interpretation to ensure rapid and accurate results. Recently, high-throughput MS data have been leveraged to advance machine learning (ML) techniques, particularly in matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS and MS imaging (MSI). The accuracy of AI models is intricately linked to the sampling techniques used in MALDI and MALDI imaging measurements. With the help of artificial neural networks, traditional barriers are being overcome, accelerating data acquisition for different applications. AI-driven analysis of chemical specificity and spatial mapping in two-dimensional datasets has gained significant attention, highlighting its potential impact. This review focuses on recent AI applications, particularly supervised ML in MALDI-TOF MS and MALDI-MSI data analysis. Additionally, this review provides an overview of sample preparation methods and sampling techniques essential for ensuring high-quality data in deep learning-based models.

Amphibians, as one of the leaders of immune resistance, have lived on Earth for hundreds of millions of years. Their dorsal glands produce a cocktail of biologically active peptides that successfully fight microorganisms and even predators. Since this mechanism prevents the development of pathogen resistance, antimicrobial peptides are very promising pharmaceuticals for future generations. Mass spectrometry is the most powerful tool for sequencing peptides/proteins. For over 30 years of studies in this field, mass spectrometry has resolved all the problems associated with the de novo sequencing of amphibian peptides. This review covers the modern de novo sequencing algorithms that enable achieving complete sequence coverage of all frog peptides, including long ones (up to 46 amino acids). Accurate mass measurements have reliably solved the problem of isobaric amino acids. Moreover, there is no longer any need to carry out any preliminary derivatization procedures such as breaking disulfide bonds or N-terminal acetylation. EThcD and ExD tools with manual spectra interpretation provide an efficient approach for reliable differentiation between isomeric leucine and isoleucine residues in the chain, using secondary w- and d-ions, and they resolve the problems of sequencing inside the intact S-S cycles.