Probing the structures of protonated and metalated glycine complexes using infrared multiple photon dissociation spectroscopy

Atkins, Chad Garry (2009) Probing the structures of protonated and metalated glycine complexes using infrared multiple photon dissociation spectroscopy. Masters thesis, Memorial University of Newfoundland.

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Abstract

The determination of gas-phase ion structures has been a prominent goal for many researchers within the field of mass spectrometry. The techniques to achieve this goal have evolved tremendously and absolute characterization is becoming an exciting reality. In the studies to be discussed, experimental results led to the conclusive assignment of a particular structure being the largest contributor of all ions present in the gas phase. -- The proton- and the sodium ion-bound glycine homodimers were studied by a combination of infrared multiple photon dissociation (IRMPD) spectroscopy in the N-H and O-H stretching region and electronic structure calculations. The IRMPD spectrum for the proton-bound dimer confirmed that the lowest-energy structure was an ion-dipole complex between N-protonated glycine and the carboxyl group of the other glycine. The IRMPD spectrum for the sodium ion-bound dimer confirmed that the lowest energy structure was two bidentate glycine molecules bound to Na+. In both cases, higher-energy structures could be ruled out using spectroscopic and/or thermodynamic arguments. -- In the second study to be discussed, IRMPD spectroscopy, collision-induced dissociation (CID) spectrometry and theoretical calculations were combined to provide new insights into the structure and dissociation of lead (II) complexed with the amino acid glycine in the presence and absence of solvent. Unexpectedly, these experiments revealed the main lead (II) coordination sites to glycine were the deprotonated amino group and the carbonyl group. Such information is useful because of the biological implications which lead (II) has towards physiological systems. Structural knowledge of this system can be extended to include other amino acids and provide insight into the coordination of lead (II) with peptides responsible for detoxification.

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