G. C. Boles, R. A. Coates, G. Berden
2015
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0
Influential Citations
17
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Journal
The journal of physical chemistry. B
Abstract
Complexes of glutamine (Gln) cationized with Zn(2+) and Cd(2+) were examined by infrared multiple photon dissociation (IRMPD) action spectroscopy using light generated from a free-electron laser. Electrospray ionization yielded complexes of deprotonated Gln with Zn(2+), [Zn(Gln-H)](+), and intact Gln with CdCl(+), CdCl(+)(Gln). For each complex, the spectra obtained were compared with those for low-energy conformers found using quantum chemical calculations to identify the structures present experimentally. Calculations were performed at the B3LYP/6-311+G(d,p) level for [Zn(Gln-H)](+) and at the B3LYP/def2-TZVP level with an SDD effective core potential on cadmium for CdCl(+)(Gln). The main binding motif observed for the Cd(2+) complex was a charge-solvated, tridentate [N,CO,COsc] structure in which the metal binds to the backbone amino group and the carbonyl oxygens of the carboxylic acid and side-chain amide groups. The Zn(2+) system similarly preferred a [N,CO(-),COsc] binding motif, where binding was observed at the carboxylate site along with the backbone amino and side-chain carbonyl groups. In both cases, the theoretically determined lowest-energy conformers explain the experimental [Zn(Gln-H)](+) and CdCl(+)(Gln) spectra well.