Synthesis and characterization of novel metal containing biomolecules through ion/ion reactions
Gas phase complexes between metal ions and biomolecules offer opportunities to study species that play significant roles in biological processes. Ion/ion reactions allow synthesis and study of metal containing gas phase biomolecular complexes. Experiments were predominantly performed in linear ion trap (LIT) hybrid instruments due to a superior ability to selectively isolate reagent ions of both polarities compared to conventional three dimensional (3-D) quadrupole ion traps, and the ability of the LIT to implement a variety of different ion/ion reaction procedures. During the thesis study, a variety of different metals and metal ion complexes have been examined for their reaction properties with both peptides and oligodeoxynucleotides (ODNs).
Chapters two and three focus on ion/ion reactions in a hybrid LIT to synthesize singly charged metalated peptides from ion/ion reactions of doubly charged peptide cations and singly charged metal salt anions, followed by a dissociation experiment to probe the fragmentation chemistry of these metalated ions. Chapter two emphasizes that dilithiated peptide complexes formed via ion/ion reactions fragment similarly to a complex formed directly from electrospray of a metal-peptide solution. Chapter three focuses on interactions of gold cations and sulfur in polypeptides containing cysteine and/or methionine residues but no disulfide bonds, and this study shows evidence for a gold-mediated even electron z-type cleavage mechanism from peptides with cysteine residues. The fourth chapter focuses on the products of ion/ion reactions of cationic transition metal complexes with oligodeoxynucleotide anions. Chapter four is an effort to understand contributions to ion/ion reaction chemistries from different reaction pathways during ion/ion reactions, including electron transfer (ET), proton transfer (PT), complex formation, and cation switching. Model oligonucleotides were hexadeoxyadenylate (hexa-dA) anions, and metal complexes studied include copper (II), iron (II), cobalt (II), and ruthenium (II), in complexes with neutral or charged organic ligands. These experimental results are examined using a model that seeks to predict relative contributions of electron transfer and metal transfer to the final ion/ion reaction product composition.