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.
Bibliographical noteFunding Information:
This work was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Science, Geosciences, and Biosciences and was performed using EMSL, a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated by the Battelle Memorial Institute for the DOE. The theoretical calculations were conducted on the EMSL Cascade Supercomputer and at the University of Minnesota Supercomputing Institute. S.R.K. acknowledges support from the National Science Foundation (CHE-1361766). The financial support from the Ministry of Science and Technology of China (no. 2012YQ220113) is also gratefully acknowledged (X.Z.).
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