Development and characterization of an atmospheric pressure ionization source matrix-assisted laser desorption electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry for analysis of biological macromolecules.
The field of mass spectrometry has grown tremendously over the past few decades due in large part to the continued application to new and interesting areas of exploration. The advent of soft ionization sources such as electrospray ionization and matrix-assisted laser desorption/ionization has dramatically increased the applications of mass spectrometry; in particular, analysis of complex biological samples. Electrospray ionization has demonstrated the capability to generate multiply-charged ions which increases the amount of information garnered from each analysis. Matrix-assisted laser desorption/ionization has demonstrated complex sample analysis requiring minimal sample preparation, which results in high throughput. As a result of these findings, there has been tremendous growth in the development of new ionization source technology in recent years for reducing sample preparation required prior to analysis for high throughput sample analysis and the generation of multiply-charged ions.;Demonstrated herein is the development and characterization of an atmospheric pressure ionization source called matrix-assisted laser desorption electrospray ionization (MALDESI). MALDESI is a hybrid combination of MALDI and ESI which utilizes laser desorption with electrospray postionization for the generation of multiply-charged ions. Multiply-charged ions are of particular importance when using Fourier transform mass spectrometry, due to the increase in resolving power and mass accuracy with increasing charge on the molecule. Positive identification of biological macromolecules is demonstrated utilizing top-down characterization of intact polypeptides as well as high mass accuracy utilizing internal calibration. A newly designed highly robust and versatile atmospheric pressure ionization platform is designed and developed for high precision analysis (i.e., imaging) and described in detail.;Solid- and liquid state analysis of three out of the four classes of biological molecules (carbohydrates, proteins, lipids) is demonstrated using the high precision versatile ionization platform. Ultraviolet and infrared MALDESI is demonstrated at various wavelengths (UV, 337 nm and 349 nm and IR, 2.94 mum and 10.6 mum) with and without ESI postionization for the generation of multiply-charged ions. The liquid-state MALDESI ionization process is characterized which may be described as laser desorption from a macroscopic electrospray droplet. MALDESI direct analysis with minimal or no sample preparation is demonstrated and applications for high throughput analysis of complex samples (i.e., glycans) are described.