Boles Georgia C, Owen Cameron J, Berden Giel, Oomens Jos, Armentrout P B
Department of Chemistry, University of Utah, 315 S. 1400 E. Rm. 2020, Salt Lake City, Utah 84112, USA.
Phys Chem Chem Phys. 2017 May 21;19(19):12394-12406. doi: 10.1039/c7cp01786c. Epub 2017 May 2.
Complexes of glutamic acid (Glu) cationized with Zn and Cd were examined by infrared multiple photon dissociation (IRMPD) action spectroscopy using light generated from a free electron laser. Complexes of deprotonated Glu with Zn, [Zn(Glu-H)ACN] (where ACN = acetonitrile, CHCN), and intact Glu with CdCl, CdCl(Glu) were formed. Notably, photodissociation induces Glu fragmentation rather than ACN loss in the Zn complex. In order to identify the structures formed experimentally, the experimentally obtained spectra were compared to those calculated from optimized structures at the B3LYP/6-311+G(d,p) level for [Zn(Glu-H)ACN] and B3LYP/def2-TZVP level with an SDD effective core potential on cadmium for the CdCl(Glu) system. The main binding motif observed for the heavy metal complex is a charge solvated, tridentate [N,CO,CO] structure where the metal binds to the backbone amino group and carbonyl oxygens of the side-chain and backbone carboxylic acid groups. The Zn system similarly prefers a [N,CO,CO] binding motif, where binding is observed at one oxygen of the backbone 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(Glu-H)ACN] and CdCl(Glu) spectra well.
利用自由电子激光产生的光，通过红外多光子解离（IRMPD）作用光谱对用锌和镉阳离子化的谷氨酸（Glu）配合物进行了研究。形成了去质子化的Glu与锌的配合物[Zn(Glu-H)ACN]（其中ACN = 乙腈，CHCN）以及完整的Glu与CdCl的配合物CdCl(Glu)。值得注意的是，光解离会导致Glu碎片化，而不是锌配合物中乙腈的损失。为了确定实验形成的结构，将实验获得的光谱与在B3LYP/6-311+G(d,p)水平下[Zn(Glu-H)ACN]的优化结构以及在B3LYP/def2-TZVP水平下对CdCl(Glu)体系在镉上使用SDD有效核势计算得到的光谱进行了比较。观察到的重金属配合物的主要结合模式是一种电荷溶剂化的三齿[N,CO,CO]结构，其中金属与主链氨基以及侧链和主链羧酸基团的羰基氧结合。锌体系同样倾向于[N,CO,CO]结合模式，在主链羧酸盐位点的一个氧原子以及主链氨基和侧链羰基处观察到结合。在这两种情况下，理论确定的最低能量构象很好地解释了实验得到的[Zn(Glu-H)ACN]和CdCl(Glu)光谱。
