Schotte, FriedrichCho, Hyun SunSoman, JayashreeWulff, MichaelOlson, John S.Anfinrud, Philip A.2014-10-082014-10-082013Schotte, Friedrich, Cho, Hyun Sun, Soman, Jayashree, et al.. "Real-time tracking of CO migration and binding in the ? and ? subunits of human hemoglobin via 150-ps time-resolved Laue crystallography." <i>Chemical Physics,</i> 422, (2013) Elsevier: 98-106. http://dx.doi.org/10.1016/j.chemphys.2012.12.030.https://hdl.handle.net/1911/77453We have developed the method of picosecond Laue crystallography and used this capability to probe ligand dynamics in tetrameric R-state hemoglobin (Hb). Time-resolved, 2 Å-resolution electron density maps of photolyzed HbCO reveal the time-dependent population of CO in the binding (A) and primary docking (B) sites of both α and β subunits from 100 ps to 10 μs. The proximity of the B site in the β subunit is about 0.25 Å closer to its A binding site, and its kBA rebinding rate (∼300 μs−1) is six times faster, suggesting distal control of the rebinding dynamics. Geminate rebinding in the β subunit exhibits both prompt and delayed geminate phases. We developed a microscopic model to quantitatively explain the observed kinetics, with three states for the α subunit and four states for the β subunit. This model provides a consistent framework for interpreting rebinding kinetics reported in prior studies of both HbCO and HbO2.engThis is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier.Journal articlehemoglobingeminate rebindingligand migrationtime-resolved Laue crystallographyhttp://dx.doi.org/10.1016/j.chemphys.2012.12.030