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Zinc and Cadmium Complexation of l‑Threonine: An Infrared Multiple Photon Dissociation Spectroscopy and Theoretical Study
Complexes of threonine (Thr) cationized with Zn2+ and Cd2+ were examined by infrared multiple photon dissociation action spectroscopy using light generated from a free electron laser. Low-energy conformers for Zn(Thr–H)+(ACN) (where ACN = acetonitrile), Zn(Gly–H)+(ACN) (formed via CO2-laser irradiat...
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Published in: | The journal of physical chemistry. B 2019-11, Vol.123 (44), p.9343-9354 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Complexes of threonine (Thr) cationized with Zn2+ and Cd2+ were examined by infrared multiple photon dissociation action spectroscopy using light generated from a free electron laser. Low-energy conformers for Zn(Thr–H)+(ACN) (where ACN = acetonitrile), Zn(Gly–H)+(ACN) (formed via CO2-laser irradiation of intact Zn(Thr–H)+(ACN)), and CdCl+(Thr) complexes were found using quantum chemical calculations in order to identify the structures formed experimentally. For all species, the predicted ground structures reproduce the experimental spectra well, where tridentate [N, CO, OHs] binding motifs were dominantly observed for the intact Zn(Thr–H)+(ACN) and CdCl+(Thr) complexes. In both of these cases, the metal center binds to the backbone amino group (N), carbonyl oxygen (CO, where this site is deprotonated in the Zn2+ complex), and side-chain hydroxyl oxygen (OHs). For the Zn2+ system, there also appears to be a population of a higher-energy species in which the side chain is deprotonated, either [N, Os –, CO] or [N, Os –, OH]. CO2-laser irradiation of Zn(Thr–H)+(ACN) leads to loss of its side chain via elimination of acetaldehyde, yielding a bidentate Zn(Gly–H)+[N, CO–](ACN) complex. Overall, this work explores the binding interactions between Thr and biologically relevant metals in a prototypical environment. Comparison of current work with previous analyses allows for the elucidation of important metal dependent trends associated with physiologically important metal–amino acid binding. |
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ISSN: | 1520-6106 1520-5207 |
DOI: | 10.1021/acs.jpcb.9b08184 |