title: Restricted rotational motion of CO in a protein internal cavity: evidence for nonseparating correlation functions from IR pump-probe spectroscopy.
abstract: The strongly restricted orientational motion of CO molecules trapped in the Xe4 internal cavity of myoglobin mutant L29W-S108L is investigated by polarization-dependent mid-infrared pump-probe spectroscopy at cryogenic temperatures. Following an ultrafast initial decay, the signal anisotropy reaches an asymptotic value that is significantly larger than the prediction from the well-known relation [see text], based on previously established potential parameters. This discrepancy is explained by showing that the full four-point correlation function describing third-order spectroscopy [see text] does not factorize in systems where its fast decay is dominated by restricted reorientation of the transition dipole moments.
authors.affiliation: Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse, 190, CH-8057 Zürich, Switzerland.
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; D002248:Carbon Monoxide / Q000737:chemistry*; D003198:Computer Simulation; D008297:Male; D008958:Models, Molecular; D009010:Monte Carlo Method; D009154:Mutation; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry; D013057:Spectrum Analysis; D014907:Whales
chemical_list: D009211:Myoglobin; D011994:Recombinant Proteins; D002248:Carbon Monoxide