Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, USA.
Phys Chem Chem Phys. 2018 Aug 8;20(31):20712-20725. doi: 10.1039/c8cp03484b.
Arginine (Arg) complexes with Zn2+ and Cd2+ were examined by infrared multiple photon dissociation (IRMPD) action spectroscopy using light from a free electron laser. Electrospray ionization generated complexes of deprotonated Arg with Zn2+, [Zn(Arg-H)]+, and Arg with CdCl+, CdCl+(Arg). Possible low-energy conformers of these species were found using quantum chemical calculations, and their calculated IR spectra were compared to experimentally measured IRMPD spectra. Calculations were performed at the B3LYP/6-311+G(d,p) level for Zn2+ complexes and B3LYP/def2-TZVP with an SDD effective core potential on cadmium for CdCl+ complexes. [Zn(Arg-H)]+ was found to adopt a charge-solvated, tridentate [N,CO-,Nω'] structure where Zn2+ binds to the backbone amine, carbonyl oxygen, and side-chain terminal guanidine nitrogen (Nω'). The CdCl+(Arg) species was suggested to be a mixture of a dominant (∼85%) charge-solvated, tridentate [N,CO,Nω'] structure where the CdCl+ binds to the backbone amine, carbonyl, and side-chain imine (Nω') and a minor (∼15%) bidentate N,CO- zwitterionic structure where the metal center binds to the backbone amine and carbonyl oxygen with intramolecular proton migration from the hydroxyl to the Nω' guanidine nitrogen (as designated in parenthesis).
精氨酸（Arg）与 Zn2+和 Cd2+的配合物通过使用自由电子激光的红外多光子解离（IRMPD）作用光谱进行了检查。电喷雾电离生成了带负电荷的 Arg 与 Zn2+的配合物[Zn(Arg-H)]+和 Arg 与 CdCl+的配合物 CdCl+(Arg)。使用量子化学计算找到了这些物种的可能低能构象，并将其计算的红外光谱与实验测量的 IRMPD 光谱进行了比较。对于 Zn2+配合物，在 B3LYP/6-311+G(d,p)水平上进行了计算，对于 CdCl+配合物，在 B3LYP/def2-TZVP 上进行了计算，其中 CdCl+配合物采用 SDD 有效核势。发现[Zn(Arg-H)]+采用带电荷的三齿[N,CO-,Nω']结构，其中 Zn2+与骨架胺、羰基氧和侧链末端胍基氮（Nω'）结合。建议 CdCl+(Arg)物种是一种主要（约 85%）带电荷的三齿[N,CO,Nω']结构的混合物，其中 CdCl+与骨架胺、羰基和侧链亚胺（Nω'）结合，而次要（约 15%）的二齿N,CO-两性离子结构，其中金属中心与骨架胺和羰基氧结合，分子内质子从羟基迁移到 Nω'胍基氮（括号内指定）。
