Design and Performance of a Novel Interface for Combined Matrix-Assisted Laser Desorption Ionization at Elevated Pressure and Electrospray Ionization with Orbitrap Mass Spectrometry

Abstract

Matrix-Assisted Laser Desorption Ionization, MALDI, has been increasingly used in a variety of biomedical applications, including tissue imaging of clinical tissue samples, and in drug discovery and development. These studies strongly depend on the performance of the analytical instrumentation and would drastically benefit from improved sensitivity, reproducibility, and mass/spatial resolution. In this work, we report on a novel combined MALDI/ESI interface, which was coupled to different Orbitrap mass spectrometers (Elite and Q Exactive Plus) and extensively characterized with peptide and protein standards, and in tissue imaging experiments. In our approach, MALDI is performed in the elevated pressure regime (5-8 Torr) at a spatial resolution of 15-30 μm, while ESI-generated ions are injected orthogonally to the interface axis. We have found that introduction of the MALDI-generated ions into an electrodynamic dual-funnel interface results in increased sensitivity characterized by a limit of detection of ∼400 zmol, while providing a mass measurement accuracy of 1 ppm and a mass resolving power of 120 000 in analysis of protein digests. In tissue imaging experiments, the MALDI/ESI interface has been employed in experiments with rat brain sections and was shown to be capable of visualizing and spatially characterizing very low abundance analytes separated only by 20 mDa. Comparison of imaging data has revealed excellent agreement between the MALDI and histological images.

Mass spectrometry is a multifaceted weapon to be used in the battle against Alzheimer's disease: Amyloid beta peptides and beyond

“…Another experimental expedient aimed to improve sensitivity and accuracy of MS screening of metabolites is the combination of MALDI at elevated pressure (EP‐MALDI) and ESI with obitrap analyzer based mass spectrometer. Indeed, in experiments with rat brain tissue sections, high sensitivity and dynamic range at a spatial resolution of 15‐20 µm have been reported for biomolecular ions separated in mass by just 10‐20 mDa, in excellent agreement with histological images …”

“…Indeed, in experiments with rat brain tissue sections, high sensitivity and dynamic range at a spatial resolution of 15-20 µm have been reported for biomolecular ions separated in mass by just 10-20 mDa, in excellent agreement with histological images. 156 As mentioned above, GC-MS investigations of metabolites have higher sensitivity, reproducibility, and resolution than in other conventional techniques, as well as a repeatable mass spectral fragmentation obtained upon electron ionization. Such reliable mass spectra fragmentation allows a straightforward identification of peaks via libraries.…”

Mass Spectrometry Imaging with Isomeric Resolution Enabled by Ozone‐Induced Dissociation

“…All MSI experiments were performed using a Orbitrap Elite mass spectrometer (Thermo Fisher Scientific GmbH, Bremen, Germany) coupled to an intermediate pressure MALDI source (Spectroglyph LLC, Kennewick, WA, USA) 19. All brain sections were coated with norharmane matrix for MALDI‐MSI analysis.…”

An On‐Tissue Paternò–Büchi Reaction for Localization of Carbon–Carbon Double Bonds in Phospholipids and Glycolipids by Matrix‐Assisted Laser‐Desorption–Ionization Mass‐Spectrometry Imaging

“…All MS data were acquired using a Q Exactive Plus Orbitrap mass spectrometer (Thermo Fisher Scientific), equipped with a modified dual MALDI/ESI Injector (Spectroglyph) . A frequency‐tripled (349 nm) Nd:YLF laser was used for MALDI with an effective spot size of about 20 μm by diameter (defined as the area of visible material ablation).…”