title: Protein ligand migration mapped by nonequilibrium 2D-IR exchange spectroscopy.
abstract: 2D-IR exchange spectroscopy has been introduced recently to map chemical exchange networks in equilibrium with subpicosecond time resolution. Here, we demonstrate the generalization of 2D-IR exchange spectroscopy to nonequilibrium systems and its application to map light-triggered migration of ligands between different sites in a protein. Within picoseconds after a photodissociating laser pulse, carbon monoxide ligands relocate from their binding site A at the heme prosthetic group of myoglobin to a primary docking site B in the distal heme pocket. Multiple CO stretching bands are observed for the CO ligand in sites A and B, indicating that several distinct conformational substates of the myoglobin:ligand complex coexist in solution. Exchange cross-peaks between the bands associated with substates of heme-bound CO and photodissociated CO in the primary docking site reveal the substate connectivity at physiological temperature.
authors.affiliation: Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. j.bredenbeck@pci.unizh.ch
authors.forename: Jens
authors.initials: J
authors.lastname: Bredenbeck
authors.forename: Jan
authors.initials: J
authors.lastname: Helbing
authors.forename: Karin
authors.initials: K
authors.lastname: Nienhaus
authors.forename: G Ulrich
authors.initials: GU
authors.lastname: Nienhaus
authors.forename: Peter
authors.initials: P
authors.lastname: Hamm
mesh_terms: D000818:Animals; D008024:Ligands; D009154:Mutation / Q000235:genetics; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013552:Swine; D014633:Valine / Q000235:genetics / Q000378:metabolism
chemical_list: D008024:Ligands; D009211:Myoglobin; D014633:Valine