Imaging mass spectrometry in transmission geometry

Abstract

Die diastereoselektive Differenzierung der beiden Methylengruppen eines cyclischen Acetals zur Erzeugung des quartären Asymmetriezentrums C22 ist das herausragende Merkmal der hoch enantioselektiven Totalsynthese von (+)‐Lasonolid A (siehe Bild). Andere Schlüsselschritte sind die Verwendung eines Sulfon‐Sulfid‐Reagens als C3‐Baustein mit zwei latenten trans‐Olefineinheiten und eine Makrocyclisierung durch intramolekulare Horner‐Emmons‐Reaktion.

A Mechanism for Ionization of Nonvolatile Compounds in Mass Spectrometry: Considerations from MALDI and Inlet Ionization

“…Even solvent-free sample preparation, used initially with Figures S2, S3) demonstrates that a laser is not necessary to produce analyte ions from matrices used in MALDI. Lasers, however, are a beneficial means of introducing sample into the inlet by ablation because the laser beam can be focused on small areas, a requirement for high resolution imaging [55].…”

Localization and imaging of gangliosides in mouse brain tissue sections by laserspray ionization inlet

“…Additionally, LSII often employs transmission geometry (TG) in which the laser is aligned 180° to the sample/orifi ce and ablates the analyte from the backside (supplementary Fig. I-C) ( 52,(64)(65)(66). This technique offers further improvements to spatial resolution and high-throughput acquisitions ( 65,66 ), as only a single laser shot is required to obtain a mass spectrum.…”

“…This technique offers further improvements to spatial resolution and high-throughput acquisitions ( 65,66 ), as only a single laser shot is required to obtain a mass spectrum. This is especially important for imaging mass spectrometry, in which LSII has recently been developed by Richards et al ( 65 ) to image phospholipids and sulfatides from mouse brain tissue using solvent-free sample preparation, inlet ionization (supplementary Fig. I) at 450°C, and detection of the singly charged negative ions.…”

“…The signals at m / z 917.4 and m / z 932.0 represent the doubly charged intact deprotonated GD1 (d18:1-18:0) and GD1 (d20:1-18:0), respectively. Singly deprotonated ions mass spectrometer is an important LSII parameter in both positive and negative ion mode detection ( 65 ). Ion abundance in LSII is increased by heating the ion transfer capillary ( 53,(68)(69)(70).…”

“…The more complex GT1 b and GQ1 b , which contain up to four sialic acids, could not be analyzed using 2,5-DHB. We speculate this is due to the high temperature requirements of 2,5-DHB when used as a LSII matrix ( 53,65,70,71 ).…”