Gas-phase ion/ion reactions in three-dimensional and two-dimensional ion traps with emphasis on oligonucleotides and polypeptides
Abstract
Electrospray ionization combined with ion/ion reactions in a quadrupole ion trap are used for the direct analysis of positive and negative oligonucleotide mixtures. It has been found that conditions for forming positive oligonucleotide ions devoid of adducts are more difficult to establish than for forming relatively clean negative oligonucleotide ions. The first part of this thesis work is focused on the study of oligonucleotide anions. Several types of charge transfer reactions, including electron transfer, proton transfer, and cation attachment, have been investigated for ion/ion reactions involving multiply charged oligonucleotide anions. Different extent of fragmentation has been observed for different reaction types and different base compositions, and it has been shown to be directly related to ion/ion reaction exothermicity. Protonated benzoquinoline has proved to be a good reagent for manipulating charge states of high-mass negative ions. Collision-induced dissociation (CID) and ion/ion reactions are applied to the fragmentation study of oligonucleotide anions. Among all the parameters, parent ion charge and base composition play major roles in determining the favorable dissociation channels of multiply charged oligonucleotide anions. We also made direct comparison between beam-type and in-trap fragmentation of oligonucleotides in a Q TRAP hybrid mass spectrometer. Ion/ion reactions in the linear ion trap (LIT) is of high interest because LIT offers significantly better ion storage efficiency for externally generated ions and offers greater ion storage capacity than three-dimensional ion traps. The second part of this thesis work deals with the modification of a commercially available LIT tandem mass spectrometer (an MDS SCIEX Q TRAP) to enable experiments that involve ion/ion reactions of polypeptides. A novel transmission mode method has been developed to perform ion/ion proton transfer reactions in the high-pressure collision cell, Q2.
Degree
Ph.D.
Advisors
McLuckey, Purdue University.
Subject Area
Analytical chemistry
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