Mass spectrometry最新文献

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.

Matrix-assisted laser desorption ionization (MALDI) and surface-assisted laser desorption ionization (SALDI) mass spectrometry (MS), which can detect biomolecules and polymers, are widely used in biochemistry and material science. Some compounds that are difficult to ionize using MALDI can be ionized using SALDI. However, it is difficult to obtain high ion yields using SALDI/MS. In this study, a fabricated platinum (Pt) film with nanostructures on the sample surface using a sputtering method was evaluated to determine the optimal metal film for ion yield in SALDI. The surface morphology of the Pt film was analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray reflectivity (XRR), and ultraviolet-visible-near-infrared (UV-Vis-NIR) reflectance spectroscopy. The SEM, AFM, and TEM images of the Pt film showed the deposited metal film giving high ion yields of polyethylene glycol (PEG) in SALDI/MS with a Pt film (Pt-SALDI) that had a rough surface. The densities and reflectivity of films were analyzed by XRR and UV-Vis-NIR. The higher ion yields of PEG were obtained by Pt-SALDI with the Pt films with lower densities and reflectivity. This indicates that the deposition conditions for the Pt films significantly improved the ion yield in Pt-SALDI/MS. The Pt-SALDI has ionization capabilities different from those of MALDI. Therefore, optimization of Pt film for SALDI/MS and the MS imaging allows more compounds to be detected with higher sensitivity.

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.

Plant alkaloids are used in a variety of medicines, such as anti-cancer drugs and analgesics. Among these plant alkaloids, galanthamine is an Amaryllidaceae type alkaloid with acetylcholinesterase inhibition activity used in the treatment of neurological diseases such as Alzheimer's disease. Although the chemical synthesis of galanthamine has been successfully achieved, Narcissus tazetta is the main source of its production. Research shows that the galanthamine content varies not only with the type of daffodil but also with the stage of development and the part of the plant. Pharmaceutical companies seek plant species with higher galanthamine content to increase pharmaceutical availability. In this study, we were able to rapidly confirm the presence of alkaloids, such as galanthamine, lycorine, and tazettine in the N. tazetta sample using the probe electrospray ionization coupled with quadrupole time-of-flight type mass spectrometry. After confirmation of the components, we then visualized the distribution of the alkaloids by mass spectrometry imaging using the atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometer. In our method, we can provide qualitative data and visualized data immediately.

Skin dryness and irritant contact dermatitis induced by the prolonged use of surgical gloves are issues faced by physicians. To address these concerns, manufacturers have introduced surgical gloves that incorporate a moisturizing component on their inner surface, resulting in documented results showing a reduction in hand dermatitis. However, the spatial distribution of moisturizers applied to surgical gloves within the integument remains unclear. Using matrix-assisted laser desorption/ionization (MALDI)-mass spectrometry imaging (MSI), we investigated the spatial distribution of moisturizers in surgical gloves within artificial membranes. Recently, dermal permeation assessments using three-dimensional models, silicone membranes, and Strat-M have gained attention as alternative approaches to animal testing. Therefore, in this study, we established an in vitro dermal permeation assessment of commercially available moisturizers in surgical gloves using artificial membranes. In this study, we offer a methodology to visualize the infiltration of moisturizers applied to surgical gloves into an artificial membrane using MALDI-MSI, while evaluating commercially available moisturizer-coated surgical gloves. Using our penetration evaluation method, we confirmed the infiltration of the moisturizers into the polyethersulfone 2 and polyolefin layers, which correspond to the epidermis and dermis of the skin, after the use of surgical gloves. The MSI-based method presented herein demonstrated the efficacy of evaluating the permeation of samples containing active ingredients.

Mass spectrometry imaging (MSI) is a technique that visualizes the distribution of molecules by ionizing the components on the surface of a sample and directly detecting them. Previously, MSI using hair has primarily been used in the forensic field to detect illegal drugs. On the other hand, there are few examples of using this technology for health monitoring. In this study, hair and clinical data were collected from 24 subjects, and the correlation between blood cholesterol levels and cholesterol detected from cross-sectional hair slices was analyzed. As a result, a positive correlation with a correlation coefficient of 0.43 was observed between blood cholesterol and cholesterol detected from hair. Furthermore, when comparing the results of fluorescence staining (FS) of hair cholesterol with Filipin III and the MSI results, it was found that while FS could visualize detailed hair structures, there were cases where the results differed from MSI, possibly due to some cholesterol loss during the staining process. In the future, if various disease biomarkers can be detected using hair MSI, it could potentially become a non-invasive diagnostic method.

Aims: The purpose of this study is to establish a novel diagnosis system in early acute coronary syndrome (ACS) using probe electrospray ionization-mass spectrometry (PESI-MS) and machine learning (ML) and to validate the diagnostic accuracy. Methods: A total of 32 serum samples derived from 16 ACS patients and 16 control patients were analyzed by PESI-MS. The acquired mass spectrum dataset was subsequently analyzed by partial least squares (PLS) regression to find the relationship between the two groups. A support vector machine, an ML method, was applied to the dataset to construct the diagnostic algorithm. Results: Control and ACS groups were separated into the two clusters in the PLS plot, indicating ACS patients differed from the control in the profile of serum composition obtained by PESI-MS. The sensitivity, specificity, and accuracy of our diagnostic system were all 93.8%, and the area under the receiver operating characteristic curve showed 0.965 (95% CI: 0.84-1). Conclusion: The PESI-MS and ML-based diagnosis system are likely an optimal solution to assist physicians in ACS diagnosis with its remarkably predictive accuracy.

The areoles and spines of cacti can be used to desorb ions of ionic liquids (ILs) by the mere action of an electric field into the atmospheric pressure (AP) interface of a mass spectrometer. The small cactus species Opuntia microdasys bears numerous very fine hairs on its areoles and tiny sharp spines that appeared suited to serve as needle electrodes sharp enough for field desorption of ions to occur. In fact, positive and negative ions of four ILs could be desorbed by a process analogous to AP field desorption (APFD). In contrast to APFD where activated field emitters are employed, the ILs were deposited onto one or two adjacent areoles by applying 1-3 µL of a dilute solution in methanol. After evaporation of the solvent, the cactus was positioned next to the spray shield electrode of a trapped ion mobility-quadrupole-time-of-flight instrument. Desorption of IL cations and IL anions, respectively, did occur as soon as the electrode was set to potentials in the order of ±4.5 kV, while the cactus at ground potential was manually positioned in front of the entrance electrode to bring the areole covered with a film of the sample into the right position. Neither did mixing of ILs occur between neighboring areoles nor did the cactus suffer any damage upon its use as a botanical field emitter.

Several database search methods have been employed in untargeted metabolomics utilizing high-resolution mass spectrometry to comprehensively annotate acquired product ion spectra. Recent technical advancements in in silico analyses have facilitated the sorting of the degree of coincidence between a query product ion spectrum, and the molecular structures in the database. However, certain search results may be false positives, necessitating a method for controlling the false discovery rate (FDR). This study proposes 4 simple methods for controlling the FDR in compound search results. Instead of preparing a decoy compound database, a decoy spectral dataset was created from the measured product-ion spectral dataset (target). Target and decoy product ion spectra were searched against an identical compound database to obtain target and decoy hits. FDR was estimated based on the number of target and decoy hits. In this study, 3 decoy generation methods, polarity switching, mirroring, and spectral sampling, were compared. Additionally, the second-rank method was examined using second-ranked hits in the target search results as decoy hits. The performances of these 4 methods were evaluated by annotating product ion spectra from the MassBank database using the SIRIUS 5 CSI:FingerID scoring method. The results indicate that the FDRs estimated using the second-rank method were the closest to the true FDR of 0.05. Using this method, a compound search was performed on 4 human metabolomic data-dependent acquisition datasets with an FDR of 0.05. The FDR-controlled compound search successfully identified several compounds not present in the Human Metabolome Database.