Cryogenic “Iodide-Tagging” Photoelectron Spectroscopy: A Sensitive Probe for Specific Binding Sites of Amino Acids
Han-Hui Zhang, Wenjin Cao, Qinqin Yuan, Xiaoguo Zhou, Marat Valiev, Steven R. Kass, Xue‐Bin Wang
Abstract
This work showcases cryogenic and temperature-dependent “iodide-tagging” photoelectron spectroscopy to probe specific binding sites of amino acids using the glycine–iodide complex (Gly·I–) as a case study. Multiple Gly·I– isomers were generated from ambient electrospray ionization and kinetically isolated in a cryogenic ion trap. These structures were characterized with temperature-dependent “iodide-tagging” negative ion photoelectron spectroscopy (NIPES), where iodide was used as the “messenger” to interpret electronic energetics and structural information of various Gly·I– isomers. Accompanied by theoretical computations and Franck–Condon simulations, a total of five cluster structures have been identified along with their various binding motifs. This work demonstrates that “iodide-tagging” NIPES is a powerful general means for probing specific binding interactions in biological molecules of interest.