Studies of complexation and properties of metal ion guests with macrocyclic hosts using electrospray ionization quadrupole ion trap mass spectrometry
This research is focused on the detection and analysis of host-guest chemistry involving primarily hosts that are novel organic compounds or cyclic peptides and guests that are metal ions. Detection and analysis are by electrospray ionization quadrupole ion trap mass spectrometry. The complexes studied are between organic host molecules such as (i) crown ethers and various analogs (modified lariat ethers, azacrown ethers, thiacrown ethers) or (ii) naturally occurring or synthetic cyclic peptides and metal ions, including alkali, alkaline earth and heavy metal ions. The signals observed in the mass spectra are used to determine the effectiveness of the complexation, the entities involved in the complexes, and the stoichiometries of these entities that occur. The soft ionization nature of electrospray ionization allows many non-covalent complexes formed in solution to be viewed in the gas phase still intact. Various sample systems have been used to determine the selectivities of complexation for various ratios of miscible solvents, extractions of metals from aqueous solution phase to a non- miscible organic phase. Other experiments studied the effects of different metal ion guests on the fragmentation behavior of hosts. Evaluation of the results of these studies have implications for determining structural features of the host which can improve selectivities and avidities of hosts for particular guest species, detection of host compounds, and peptide residue sequencing, which have applications in fields of science such as chemical sensor development, biochemistry and environmental remediation.