Mass spectrometry最新文献

The molecular ion M^+· was observed when the liquid sample of butyrophenone was supplied using atmospheric pressure corona discharge (APCD). In contrast, the vapor supply resulted in the formation of the protonated molecule [M+H]⁺. The mass spectrum obtained with the liquid supply showed two distinctive fragment ions at m/z 105 and 120, resulting from α-cleavage and McLafferty rearrangement (McLR), respectively. The APCD spectrum showed peaks of M^+· and the characteristic two fragment ions that were the same as the field ionization mass spectra of butyrophenone as reported by Chait et al. and Beckey et al. The formation of the molecular and fragment ions strongly indicated that high-electric field tunnel ionization (HEFTI) occurs by the HEF strength exceeding 10⁸ V/m at the tip of the corona needle in APCD. The charge and spin density distributions of the molecular and fragment ions were analyzed by quantum chemical calculations using time-dependent density functional theory (TDDFT) and natural bond orbital (NBO) analysis.

A method for the rapid determination of α-tocopherol (α-T) and its oxidative products in plant tissue has been developed using supercritical fluid extraction (SFE) coupled with supercritical fluid chromatography (SFC) and medium vacuum chemical ionization (MVCI) with tandem mass spectrometry. The method is designed to study changes in levels for α-T and its oxidative products in plant cells during photosynthesis, aiming to observe the light response curves. α-T oxidation is a non-enzymatic self-defense mechanism in plant cells. Unlike enzyme-involved reactions, it cannot be stopped, so the oxidation continues in crude extracts even after extraction. Therefore, a real-time in-situ method is essential for tracking the light response curves. To optimize the selective reaction monitoring method, the reaction mixture of α-T and singlet oxygen (¹O₂), generated by rose Bengal under light illumination, was used as the source of oxidative products. The relative abundance changes in α-tocopherylquinone and 8a-hydroperoxy tocopherone in Pisum sativum L. (Pea) leaves under excessive light illumination have been preliminarily analyzed as part of the light response curve study. The method archives a throughput of 10-15 minutes for analyzing duplicate leaf samples. This process includes cutting off the leaf, sectioning it, placing the sample in a frozen SFE vessel, and conducting SFE/SFC analysis. Consequently, the average throughput is approximately 5-7 minutes per sample.

We developed a rapid, accurate, and quantitative method for analyzing glucosinolates (GSLs) by combining column-free liquid chromatography (LC) with direct-infusion mass spectrometry (MS). Conventional methods for analyzing GSLs take a long time (20-50 min per sample) to perform compound separation on an LC column. We achieved a shortened analysis time of 30 seconds per sample using a direct-infusion method. Samples were continuously injected by a pump and autosampler on an LC system directly into the MS. Orbitrap MS detected 11 types of GSLs in the extracts of turnip hypocotyls. The calibration curve of a GSL standard showed a linear response over a 6-digit concentration range from 1 nM to 1 mM. In addition, no decrease in the detected intensity of GSL ions in 100 continuous analyses of turnip extracts was observed. This method may be applied for rapid analysis of GSLs and other health-functional or bioactive compounds.

In our previous work, pulsed nano-electrospray ionization was applied to aqueous mixtures of 5 × 10^-6 M angiotensin II (A), bradykinin (B), and gramicidin S (G). It was found that G was totally suppressed by the presence of A and B. In this work, mixtures of A, B, and G in water/acetonitrile (W/AcN) were investigated by pulsed nano-electrospray ionization. It was found that G and A were detected as major ions, but B was almost totally suppressed by the addition of 1% acetic acid in the W/AcN solution. In contrast, B was detected as one of the major ions for the solution with the addition of 10 mM ammonium acetate. These results were interpreted based on the solvent effect. While the hydration of ornithine -NH₃ ⁺ in aqueous solution makes the ion most hydrophilic, solvation of ornithine -NH₃ ⁺ by AcN in W/AcN makes the ion solvophobic and surface active.

Many previous studies have reported various phospholipids and elements that affect sake production; however, it seems to be challenging to investigate individual types in each rice variety due to their high diversity, not to mention their distribution patterns. Since its introduction, mass spectrometry imaging (MSI) has gained attention in various fields as a simple compound visualization technique. The current study highlights the progress of powerful MSI in comprehensively analyzing phospholipids and minerals in brown rice for sake production. Multivariate analysis suggested phospholipids relating to each rice group based on regions of interest. Phospholipid classes connected with embryo and endosperm included fatty acylcarnitine, diacylglycerol, phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine. Meanwhile, the studied rice groups showed the same distribution of the investigated 12 minerals. This is the first study that reports a comprehensive imaging analysis of phospholipids and elements in brown rice for several cultivars for sake production.

Choline-containing compounds are essential nutrients for human activity, as they are involved in many biological processes, including cell membrane organization, methyl group donation, neurotransmission, signal transduction, lipid transport, and metabolism. These compounds are normally obtained from food. Fermented brown rice and rice bran with Aspergillus oryzae (FBRA) is a fermented food product derived from rice and rice ingredients. FBRA exhibits a multitude of functional properties with respect to the health sciences. This study has a particular focus on choline-containing compounds. We first developed a simultaneous liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis method for seven choline-containing compounds. The method was subsequently applied to FBRA and its ingredients. Hydrophilic interaction chromatography (HILIC) and selected reaction monitoring were employed for the simultaneous analysis of seven choline-containing compounds. MS ion source conditions were optimized in positive ion mode, and the product ions derived from the choline group were obtained through MS/MS optimization. Under optimized HILIC conditions, the peaks exhibited good shape without peak tailing. Calibration curves demonstrated high linearity across a 300- to 10,000-fold concentration range. The application of the method to FBRA and other ingredients revealed significant differences between food with and without fermentation. In particular, betaine and α-glycerophosphocholine were found to be highest in FBRA and brown rice malt, respectively. The results indicated that the fermentation processing of rice ingredients results in alterations to the choline-containing compounds present in foods. The developed HILIC/MS/MS method proved to be a valuable tool for elucidating the composition of choline-containing compounds in foods.

A novel ionization technique named medium vacuum chemical ionization (MVCI) mass spectrometry (MS), which is a chemical ionization using oxonium (H₃O⁺) and hydroxide (OH^-) formed from water, has excellent compatibility with the supercritical fluid extraction (SFE)/supercritical fluid chromatography (SFC). We have studied a method to determine free fatty acids (FFAs) in a small section of bovine liver tissue using SFE/SFC-MVCI MS analysis without further sample preparation. A series of FFA molecules interact with the C18 stationary phase, exhibiting broad chromatographic peaks when using a non-modified CO₂ as the mobile phase. It can be optimized by adding a small content of methanol to the mobile phase as a modifier; however, it may dampen the ionization efficiency of MVCI since the proton affinity of methanol is slightly higher than water. We have carefully evaluated the modifier content on the ion detection and column efficiencies. The obtained result showed that an optimized performance was in the range of 1 to 2% methanol-modified CO₂ mobile phase for both column efficiency and peak intensity. Higher methanol content than 2% degrades both peak intensity and column efficiency. Using optimized SFC conditions, a section of bovine liver tissue sliced for 14 µm thickness by 1 mm square, which is roughly estimated as about 3300 hepatocytes, was applied to determine 18 FFAs amounts for carbon chains of C12-C24. An amount of each tested FFA was estimated as in the range of 0.07 to 2.6 fmol per cell.

Among the most typical posttranslational modifications is glycosylation, which often involves the covalent binding of an oligosaccharide (glycan) to either an asparagine (N-linked) or a serine/threonine (O-linked) residue. Studies imply that the N-glycan portion of a glycoprotein could serve as a particular disease biomarker rather than the protein itself because N-linked glycans have been widely recognized to evolve with the advancement of tumors and other diseases. N-glycans found on protein asparagine sites have been especially significant. Since N-glycans play clearly defined functions in the folding of proteins, cellular transport, and transmission of signals, modifications to them have been linked to several illnesses. However, because these N-glycans' production is not template driven, they have a substantial morphological range, rendering it difficult to distinguish the species that are most relevant to biology and medicine using standard techniques. Mass spectrometry (MS) techniques have emerged as effective analytical tools for investigating the role of glycosylation in health and illness. This is due to developments in MS equipment, data collection, and sample handling techniques. By recording the spatial dimension of a glycan's distribution in situ, mass spectrometry imaging (MSI) builds atop existing methods while offering added knowledge concerning the structure and functionality of biomolecules. In this review article, we address the current development of glycan MSI, starting with the most used tissue imaging techniques and ionization sources before proceeding on to a discussion on applications and concluding with implications for clinical research.

This study investigates the mass spectrometric analysis of 10 novel amidoamine oxide compounds, which are innovative hydrogelators for polar solvents. This research aims to identify characteristic fragment patterns for these amide compounds using high-resolution mass spectrometry. Methanol solutions of the compounds were analyzed in positive and negative ion modes, and MS1 and MS2 spectra at 6 collision energy levels were obtained via electrospray ionization and hybrid tandem mass spectrometry. The importance of low-intensity peaks in structure elucidation was emphasized because low-intensity fragments could provide crucial structural information, especially for compounds with similar structures. Chain-length-dependent fragmentation patterns were observed, which could aid in predicting the structures of related compounds. This research highlights the challenges of balancing informative low-intensity peaks with accurate spectral matching in databases. Based on our results, combining mass spectrometry with separation techniques, such as liquid chromatography, could enhance structural elucidation for unknown compounds. This study contributes to the broader field of mass spectrometry and structural chemistry, particularly in the analysis of amide compounds, and future directions are proposed for developing robust algorithms for selecting and interpreting low-intensity peaks to improve compound identification in complex mixtures.

In this study, we employed platinum-assisted surface-assisted laser desorption/ionization mass spectrometry imaging (MSI) (Pt-SALDI-MSI) to detect and visualize the spatial distribution of antioxidant additives and organic dyes in polystyrene films undergoing photodegradation. In traditional matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), matrix-derived ion peaks often obscure signals from low-molecular-weight analytes. Pt-SALDI-MSI, which utilizes inorganic nanoparticles instead of an organic matrix, enables the interference-free analysis of low-molecular-weight compounds, thereby addressing the limitation of traditional MALDI-MS. Using Pt-SALDI-MSI, we observed the degradation and distribution of Irganox 1098 (an antioxidant) and crystal violet (an organic dye) following ultraviolet irradiation. This method effectively captures the photodegradation process, providing valuable insights into the environmental breakdown of plastics and the formation of microplastics.