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Dr Tamer ShoeibVisiting Research Fellow Associate Professor Tamer Shoeib is a visiting Research Fellow in the Atomic Spectrometry Research Group which forms part of the Centre for Analytical Science. Research Interests: Analytical chemistry, biophysical chemistry and molecular structure with the goal of understanding the structure, reactivity, and function of metal-containing bio-molecules. Current research focus includes the following areas: Mechanisms of metal-containing amino acid and peptide ion fragmentation Some metal-containing complexes can serve as models for metallothioneins, a class of low molecular weight proteins that have the capacity to bind both physiological (Zn, Cu, Se,...) and xenobiotic (Cd, Hg, Ag,...) heavy metals. Ion trap and triple quadrupole mass spectrometry are used to elucidate the structures of these complexes and to induce their fragmentation via collision-induced dissociation (CID), the resulting products are examined for common fragment ions and neutral loss species that might be indicative of universal fragmentation pathways. Metal cation-π interactions and molecular radical cations of peptides This non-covalent binding is important in molecular recognition by biological receptors, in enzyme catalysis and in the design of novel ionophores. The interaction of a metal cation with the π-system of an amino acid or peptide is often present in the lowest energy conformer of the complex. Ion mobility mass spectrometry techniques are used to investigate the degree of retention of these interactions in the gas-phase, while ion trap and triple quadrupole mass spectrometry are used to study the CID generated radical and distonic cations. Zwitterion and Salt-bridge Structures Amino acids exist as zwitterions in the aqueous phase, whereas their neutral forms are more stable in the gas phase. The presence of a metal cation, stabilizes the zwitterions of amino acids by forming salt bridges which are often formed in the interior of proteins and strongly influence conformation. Both experiment and theory are used to investigate the structure of amino acids and small peptides as a function of cation size and change, as well as solvation extent to determine the role of electric field and solvent on zwitterion stability. Computational Chemistry Computational modeling techniques such as ab initio and density functional theory are employed to provide details of metal's attachment site(s) to a substrate as well as various thermodynamic properties of reactions. This data often lends further credence to experimental structural assignments and provides additional insight into observed fragmentation pathways. Selected Publications:
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