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.

[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.

[This corrects the article DOI: 10.5702/massspectrometry.A0145.].

In matrix-assisted laser desorption ionization mass spectrometry, a suitable matrix is often selected for the analyte. Herein, we first developed a novel matrix, alkylated hydroxychalcone (AHC), which has properties similar to alkylated trihydroxyacetophenone (ATHAP) (Anal. Chem., 85: 9444-9448, 2013) developed as a matrix for hydrophobic peptides. However, the sample-to-sample reproducibility was low because of the poor crystallinity of AHC. The crystalline morphology of AHC changed when AHC/2,5-dihydroxybenzoic acid (DHB) was used as a binary matrix. As a result, the use of AHC/DHB improved sample-to-sample reproducibility and increased sensitivity for hydrophobic peptides. Mass imaging indicated that these results were due to an increased number of sweet spots wherein the analytes were detected as ion peaks, in a matrix/analyte crystal spot.

The appearance of the characteristic peak of the hydride-eliminated molecule [M-H]⁺ under a positive ion mode (positive) fast atom bombardment (FAB) ionization condition and liquid-assisted secondary ion mass spectrometry (LSIMS) conditions is known for some compounds and the mechanism of its formation has been investigated. In this study, we investigated the formation mechanism of the hydride-eliminated molecule [M-H]⁺ from 4-substituted-1-(methoxymethyl)benzene under a positive FAB ionization condition. The mass spectra of 4-methoxy-1-(methoxymethyl)benzene (1), 4-methoxy-1-(methoxymethyl-d ₂-)benzene (1-d ₂), and 4-methoxy-1-(methoxymethyl-d ₃)benzene (1-d ₃) were measured under the positive FAB conditions. [M-H]⁺ was observed for 1 and 1-d ₃, and [M-D]⁺ for 1-d ₂, indicating that the site of hydride elimination was the methylene of the 1-(methoxymethyl) moiety. Since [M-H]⁺ was hardly observed under the conditions of positive electron ionization and positive chemical ionization in the gas phase, the hydride elimination is a reaction specific to positive FAB ionization. To examine the contribution of the 4-substituent to the hydride elimination reaction, the mass spectra of (methoxymethyl)benzene (2) and 4-nitro-1-(methoxymethyl)benzene (3) were measured using the positive FAB. The ordering of the relative peak intensity of [M-H]⁺ for [M+H]⁺ in the FAB mass spectra was 1 > 2 > 3, and the results suggest that the electron-donating power of the substituents is an important factor in the formation of [M-H]⁺.

Scorpion venoms contain a variety of peptides that exhibit toxicity toward insects or mammals by acting on ion channels. We previously isolated four insecticidal peptides (Bl-1, Bl-2, Bl-3, and Bl-4) from the venom of Buthacus leptochelys. Among these, the complete amino acid sequence of Bl-1 was determined, whereas only N-terminal partial sequences were obtained for the others. In the present study, we determined the complete sequence of Bl-3 through de novo sequencing of enzymatically digested fragments. The discrimination between Leu and Ile was achieved based on side-chain fragmentation observed under high-energy collision-induced dissociation conditions. Bl-3 was identified as a 65-residue peptide containing four disulfide bonds. During the sequencing analysis, deamidation of the Asn residue at position 30 was observed, which is likely to have occurred after the purification step. Sequence comparison revealed that Bl-3 shares high similarity with α-toxins that act on sodium channels and exhibit nonselective toxicity toward both insects and mammals. These findings suggest that Bl-3 is likely to exert nonselective toxicity through a mechanism similar to that of α-toxins.