Mass spectrometry最新文献

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.

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.

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.

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.

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.

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.

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.

A simple and rapid analytical method was developed for the simultaneous determination of two chromium species, Cr(III) and Cr(VI), in the environmental waters by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). This study incorporated a chelating pretreatment with 2,6-pyridinedicarboxylic acid (PDCA) to convert Cr(III) species into a stable Cr(III)-PDCA anion complex, which was then separated from Cr(VI) oxyanion using an anion exchange column. Building on the fundamental analytical approach proposed by Shigeta et al. (doi: 10.2116/analsci.18P012), the mobile phase was optimized to ensure stability for ICP-MS detection, avoiding nonvolatile salts. Chromium species and chloride ions were effectively separated within 6 minutes at a flow rate of 0.6 mL min^-1 with the optimized mobile phase, which consisted of 50 mmol L^-1 ammonium acetate (pH 6.80) and 2 mmol L^-1 PDCA. The detection limits were 0.18 μg L^-1 and 0.09 μg L^-1 for Cr(III) and Cr(VI), respectively, at m/z 52 under He collision mode.

Intermolecular interactions between aromatic amino acids were investigated by ultraviolet photodissociation spectroscopy of hydrogen-bonded protonated clusters of histidine (His) and tryptophan (Trp) enantiomers in the gas phase. Product ion spectra and photodissociation spectra in the wavelength range of the S₁-S₀ transition of Trp at several temperatures (8-100 K) were obtained using a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. l-Trp detachment forming protonated His was the main pathway. Two bands observed at 288 and 285 nm in the photodissociation spectra of heterochiral H⁺(d-His)(l-Trp) indicated the coexistence of two types of conformers. The bands at 288 and 285 nm were attributed to the conformers formed from stronger and weaker intermolecular interactions, respectively. In the spectra of homochiral H⁺(l-His)(l-Trp), only the band due to the stronger interactions was observed at 288 nm. The intermolecular interactions of l-His with l-Trp were stronger than those of d-His with l-Trp.

In the interpretation step of mass spectra obtained from synthetic polymers, isotope peaks are typically intense and cannot be ignored, especially in the higher mass range. To reduce the complexity of the spectra, deisotope processing is used. In this study, a deisotope processing method that is effective even for mixtures of different types of polymers is investigated.