Correlation between internal motion and emission kinetics of tryptophan residues in proteins.
Time-resolved fluorescence anisotropy measurements of tryptophan residues were carried out for 44 proteins. Internal rotational motion with a sub-nanosecond correlation time (0.9 +/- 0.6 ns at 10 degrees C) was seen in a large number of proteins, though its amplitude varied from protein to protein. It was found that tryptophan residues which were almost fixed within a protein had either a long (greater than 4 ns) or short (less than 2 ns) fluorescence lifetime, whereas a residue undergoing a large internal motion had an intermediate lifetime (1.5-3 ns). It is suggested that the emission kinetics of a tryptophan residue is coupled with its internal motion. In particular, an immobile tryptophan residue emitting at long wavelength was characterized by a long lifetime (greater than 4 ns). It appears that a tryptophan residue fixed in a polar region has little chance of being quenched by neighboring groups.
Kouyama
T
T
Institute of Physical and Chemical Research, Saitama, Japan.
Kinosita
K
K
Ikegami
A
A
D005454:Fluorescence Polarization; D007700:Kinetics; D009904:Optical Rotation; D011506:Proteins / Q000032:analysis*; D014364:Tryptophan / Q000032:analysis*
D011506:Proteins; D014364:Tryptophan