title: Microsecond protein dynamics observed at the single-molecule level.
abstract: How polypeptide chains acquire specific conformations to realize unique biological functions is a central problem of protein science. Single-molecule spectroscopy, combined with fluorescence resonance energy transfer, is utilized to study the conformational heterogeneity and the state-to-state transition dynamics of proteins on the submillisecond to second timescales. However, observation of the dynamics on the microsecond timescale is still very challenging. This timescale is important because the elementary processes of protein dynamics take place and direct comparison between experiment and simulation is possible. Here we report a new single-molecule technique to reveal the microsecond structural dynamics of proteins through correlation of the fluorescence lifetime. This method, two-dimensional fluorescence lifetime correlation spectroscopy, is applied to clarify the conformational dynamics of cytochrome c. Three conformational ensembles and the microsecond transitions in each ensemble are indicated from the correlation signal, demonstrating the importance of quantifying microsecond dynamics of proteins on the folding free energy landscape.
authors.affiliation: Molecular Spectroscopy Laboratory, RIKEN, 2-1, Hirosawa, Wako 351-0198, Japan.
authors.forename: Takuhiro
authors.initials: T
authors.lastname: Otosu
authors.affiliation: Molecular Spectroscopy Laboratory, RIKEN, 2-1, Hirosawa, Wako 351-0198, Japan.|Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1, Hirosawa, Wako 351-0198, Japan.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Ishii
authors.affiliation: Molecular Spectroscopy Laboratory, RIKEN, 2-1, Hirosawa, Wako 351-0198, Japan.|Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1, Hirosawa, Wako 351-0198, Japan.
authors.forename: Tahei
authors.initials: T
authors.lastname: Tahara
mesh_terms: D045304:Cytochromes c / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D045304:Cytochromes c