Experimental and Theoretical Investigations of Infrared Multiple Photon Dissociation Spectra of Glutamine Complexes with Zn2+ and Cd2+

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• 作者：Georgia C. Boles ; Rebecca A. Coates ; Giel Berden ; Jos Oomens ; P. B. Armentrout
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：September 3, 2015
• 年：2015
• 卷：119
• 期：35
• 页码：11607-11617
• 全文大小：498K
• ISSN：1520-5207

文摘

Complexes of glutamine (Gln) cationized with Zn²⁺ and Cd²⁺ 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 Zn²⁺, [Zn(Gln鈥揌)]⁺, 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鈥揌)]⁺ 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 Cd²⁺ complex was a charge-solvated, tridentate [N,CO,CO_sc] 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 Zn²⁺ system similarly preferred a [N,CO^{鈥?/sup>,CO_sc] 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鈥揌)]+ and CdCl+(Gln) spectra well.}