Gas-Phase Ion/Ion Reaction of Biomolecules

Mack Shih, Purdue University

Abstract

Mass spectrometry is a versatile, powerful analytical tool for chemical and biomolecule identification, quantitation, and structural analysis. Tandem mass spectrometry is key component in expanding the capabilities of mass spectrometry beyond just a molecular weight detector. Another key component is the discovery of electrospray ionization allowing not only liquid samples to be ionized but also generation of multiply charged ions enabling mass spectrometry analysis of large biomolecules. The fragmentation pathway of ion during tandem mass spectrometry is highly dependent on the nature of the ion as well as the form of dissociation technique employed. To-date, no single form of ion or dissociation method can provide all the structure information needed; therefore, it is common to use multiple forms of ions, different charge carrier or modifications, with a variety of other dissociation techniques to generate complimentary information. Practically, it is not always easy to generate the desired form of ion via ionization methods and is one of the limitations. Gas-phase ion/ion reactions provide an easy approach in manipulation of ions, either through changing the ion type or covalent modifications, in the gas-phase with the goal of enhancing the capabilities of mass spectrometers for either molecular weight or structural analysis. In this dissertation, studies of new gas-phase ion/ion chemistry for biomolecules such as carbohydrates and phopho/sulfopeptides were performed, and exploration into mass spectrometry analysis of IgGs is discussed. Ion/ion reactions with carbohydrates were investigated with the goal of finding a chargetransfer or covalent modification reaction which can increase the structural information of carbohydrates upon tandem mass spectrometry. No luck was achieved with charge transfer ion/ion reactions which increased the overall fragmentation information in tandem mass spectrometry. Novel gas-phase covalent chemistry was discovered where alkoxides were found to form ester and ethers. It was also discovered the aldehyde functional group at the reducing end of carbohydrates are susceptible to Schiff-base modifications. Schiff-base has been previously reported in peptides and this is the first time it has been discovered for carbohydrates. In the next project a gas-phase approach for the rapid screening of polypeptide anions for phosphorylation or sulfonation based on binding strengths to guanidinium-containing reagent ions was developed. The approach relies on the generation of a complex via reaction of mixtures of deprotonated polypeptide anions with dicationic guanidinium-containing reagent ions and subsequent dipolar DC collisional activation of the complexes. The relative strengths of the electrostatic interactions of guanidinium with deprotonated acidic sites follows the order carboxylate

Degree

Ph.D.

Advisors

Mcluckey, Purdue University.

Subject Area

Chemistry|Energy|Analytical chemistry|Atomic physics|Electromagnetics|Pharmaceutical sciences|Physics

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