High-resolution multi-reflection time-of-flight mass spectrometer with atmospheric pressure interface.

RATIONALE: Atmospheric pressure interface multi-reflection time-of-flight mass spectrometry (API-MRTOF-MS) has the potential to be a rapid and high-resolution analytical tool for versatile applications in chemistry, biology, environmental science, and medicine. METHODS: The ions were reflected in a mass analyzer via electrostatic mirrors and folded flight path. Therefore, flight distances were significantly increased. The ion flight path of the API-MRTOF-MS was extended from meters to over 1 km, and the mass resolution was increased. Furthermore, the mass analysis could be completed at around 10 ms due to the rapid response of TOF-MS. RESULTS: A high-resolution API-MRTOF-MS approach is successfully developed in this study. The mass resolution could achieve 116 050 (full widths at half maximum [FWHM]) for Cs+ ions using an atmospheric pressure electrospray ionization within a total TOF of only 18 ms. An ion transmission efficiency of over 50% was achieved after 600 cycles. CONCLUSIONS: The analytical performance of the newly developed API-MRTOF-MS demonstrated that it is suitable for high resolution and rapid analysis in many fields.

Unlocking the Molecular Variations of a Micron-Scale Amyloid Plaque in an Early Stage Alzheimer's Disease by a Cellular-Resolution Mass Spectrometry Imaging Platform.

Uncovering the molecular changes at the site where Aß is deposited plays a critical role in advancing the diagnosis and treatment of Alzheimer's disease. However, there is currently a lack of a suitable label-free imaging method with a high spatial resolution for brain tissue analysis. In this study, we propose a modified desorption electrospray ionization (DESI) mass spectrometry imaging (MSI) method, called segmented temperature-controlled DESI (STC-DESI), to achieve high-resolution and high-sensitivity spatial metabolomics observation by precisely controlling desorption and ionization temperatures. By concentrating the spray plume and accelerating solvent evaporation at different temperatures, we achieved an impressive spatial resolution of 20 µm that enables direct observation of the heterogeneity around a single cell or an individual Aß plaque and an exciting sensitivity that allows a variety of low-abundance metabolites and less ionizable neutral lipids to be detected. We applied this STC-DESI method to analyze the brains of transgenic AD mice and identified molecular changes associated with individual Aß aggregates. More importantly, our study provides the first evidence that carnosine is significantly depleted and 5-caffeoylquinic acid (5-CQA) levels rise sharply around Aß deposits. These observations highlight the potential of carnosine as a sensitive molecular probe for clinical magnetic resonance imaging diagnosis and the potential of 5-CQA as an efficient therapeutic strategy for Aß clearance in the early AD stage. Overall, our findings demonstrate the effectiveness of our STC-DESI method and shed light on the potential roles of these molecules in AD pathology, specifically in cellular endocytosis, gray matter network disruption, and paravascular Aß clearance.