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An investigation of inter-ligand coordination and flexibility: IRMPD spectroscopic and theoretical evaluation of calcium and nickel histidine dimers
Journal of Molecular Spectroscopy ( IF 1.4 ) Pub Date : 2021-09-07 , DOI: 10.1016/j.jms.2021.111532
Brandon C. Stevenson 1 , Katrin Peckelsen 2 , Jonathan Martens 3 , Giel Berden 3 , Jos Oomens 3, 4 , Mathias Schäfer 2 , P.B. Armentrout 1
Affiliation  

Metallated gas-phase structures consisting of an intact and deprotonated histidine (His) ligand, M(His-H)(His)+, where M = Ca and Ni, were examined using infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light from a free-electron laser (FEL). In parallel, ab initio quantum-chemical calculations identified several low-energy isomers for each complex. Experimental action spectra were compared to linear absorption spectra calculated at the B3LYP level of theory, using the 6-311+G(d,p) basis set. Single-point energies were calculated at B3LYP, B3LYP-GD3BJ, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set. For Ca(His-H)(His)+, the dominant structure has the metal center coordinating with the π nitrogen of the imidazole ring (Nπ) and both oxygen atoms of the carboxylate group of the deprotonated His ligand while coordinating with the backbone amine (Nα), Nπ, and the carbonyl oxygen of the carboxylic acid of the intact His ligand. The Ni(His-H)(His)+ species coordinates the metal ion through Nα, Nπ, and the carbonyl oxygen for both the deprotonated and intact His ligands, but also shows evidence for a minor secondary structure where the deprotonated His coordinates the metal at Nα, Nπ, and the deprotonated carbonyl oxygen and the intact His ligand is zwitterionic, coordinating the metal with both carboxylate oxygens. Different levels of theory predict different ground structures, highlighting the need for utilizing multiple levels of theory to help identify the gas-phase structure actually observed experimentally.



中文翻译:

配体间协调和灵活性的研究:钙和镍组氨酸二聚体的 IRMPD 光谱和理论评估

金属化的气相结构包括完整的和去质子化的组氨酸(His)的配位体,M(他-H)(他的)+,其中M = Ca和镍,采用利用来自光红外线的多个光子解离(IRMPD)动作光谱法检测自由电子激光器(FEL)。同时,从头算量子化学计算确定了每个复合物的几种低能异构体。使用 6-311+G(d,p) 基组,将实验作用光谱与在 B3LYP 理论水平计算的线性吸收光谱进行比较。使用 6-311+G(2d,2p) 基组计算 B3LYP、B3LYP-GD3BJ、B3P86 和 MP2(full) 水平的单点能量。对于 Ca(His-H)(His) +,主要结构的金属中心与咪唑环的 π 氮(N π)和去质子化的 His 配体的羧酸根的两个氧原子配位,同时与主链胺(N α)、N π和完整His配体的羧酸的羰基氧。Ni(His-H)(His) +物种通过 N α、N π和羰基氧对去质子化和完整 His 配体的金属离子进行配位,但也显示了去质子化 His 配位的次要二级结构的证据N α , N π处的金属,并且去质子化的羰基氧和完整的 His 配体是两性离子的,使金属与两个羧酸根氧配位。不同层次的理论预测不同的地面结构,强调需要利用多层次的理论来帮助识别实验中实际观察到的气相结构。

更新日期:2021-09-13
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