Application of the Orbitrap mass analyzer to targeted proteomics and gas chromatography/mass spectrometry of small molecules.

摘要

The work described herein spans two disparate topics: 1) the use of a high resolution and accurate mass analyzer to facilitate targeted proteomic methods, and 2) the development and applications of novel instrumentation for high resolution gas chromatography/mass spectrometry. While disparate, a common theme of a high resolution and accurate mass analyzer, the Orbitrap, ties the work together into, broadly, a treatise on the benefits of high resolution and accurate mass measurements in mass spectrometric research.;In Chapter 1, I present an introduction on the Orbitrap mass analyzer and motivate the need for high resolution and accurate mass measurements in mass spectrometry. I will discuss the theory of Orbitrap operation, as well as the practical factors that may enhance or limit its performance. In Chapter 2, I delve into the field of targeted proteomics with the introduction of the “parallel reaction monitoring” (PRM) analysis paradigm using a bench-top quadrupole-Orbitrap LC/MS. While targeted proteomics is usually the domain of low resolution but highly sensitive mass analyzers, I demonstrate the utility of high resolution with a direct comparison to the “gold-standard” triple-quadrupole MS-based selected reaction monitoring (SRM) approach. This PRM approach has already generated much interest in the proteomics community since its publication.;In Chapters 3 through 5, I transition to GC/MS, another field dominated by low resolution and fast scanning mass analyzers. In Chapter 3, I detail the construction and characterization of a proof-of-principle instrument for high resolution GC/MS built using an electron transfer dissociation (ETD)-enabled quadrupole linear ion trap (QLT)-Orbitrap MS. While the performance of this instrument was hindered by its design, the benefits of the Orbitrap for unambiguous elemental composition assignment to small molecules were clear, and further development was deemed warranted. In Chapter 4, I detail that further development in the design and construction of a dedicated, applications-grade bench-top quadrupole-Orbitrap GC/MS. The application of this instrument to the non-targeted characterization of unknown metabolites is presented in Chapter 5. Additionally in Chapter 5, I introduce a new method for data-dependent acquisition termed “molecular-ion directed acquisition”, which aims to maximize the information content from non-targeted tandem MS in metabolomic studies.