Restricted rotational motion of CO in a protein internal cavity: evidence for nonseparating correlation functions from IR pump-probe spectroscopy.
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.
Helbing
Jan
J
Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse, 190, CH-8057 Zürich, Switzerland.
Nienhaus
Karin
K
Nienhaus
G Ulrich
GU
Hamm
Peter
P
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
D009211:Myoglobin; D011994:Recombinant Proteins; D002248:Carbon Monoxide