UV-induced online photochemical reactions for enhanced biomolecule structural characterization on an ESI MS/MS platform
Abstract
Mass spectrometry (MS), when combined with atmospheric pressure ionization (API) sources such as electrospray ionization (ESI), has become a premier tool in the analysis of thermally labile biomolecules as gas phase ions via separation by mass to charge (m/z). Unambiguous structural identification can provide deep insight into the biological function of the analyte biomolecule and is critical during analysis. To obtain ion structural information reactions must be performed as m/z alone provides only ion molecular formula. Analyte reactions can occur under vacuum with m/z selected ions or at atmospheric pressure (AP) in the solution or gas phase. Often a combination of both is used in analysis for maximum analyte structural information. In this dissertation a new method is presented to enhance biomolecule structural selectivity using an ESI MS/MS platform via AP reactions. During ESI UV-induced derivatizations / degradations of biomolecules are effected in the solution / plume and analyzed via MS/MS collision-induced dissociation (CID). A total of four reactions are described in the dissertation: two involving radical-induced disulfide bond cleavage to enhance peptide sequence information and two reactions to locate carbon-carbon double bonds in unsaturated lipids via site-specific alkene reaction. For all reactions small molecules (e.g., dioxygen and/or ESI solvent) were initially photo excited and directly or indirectly reacted with the analyte. Fused silica capillary or borosilicate glass emitters (nanoESI) were used as online reactors to induce UV reactions in the solution, resulting in reaction yields ? 50%. Products were formed on the s timescale and using various reactor designs reactions were implemented over flow rates ranging from 20 nL/min – 20 µL/min. Under optimized conditions the reactions had negligible impact to ESI performance which potentially allows for seamless coupling into established analytical workflows. In addition, the reaction setup is relatively low in cost, easy to implement, and requires no instrument modifications.
Degree
Ph.D.
Advisors
Xia, Purdue University.
Subject Area
Physical chemistry
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