1: Eur J Biochem  1989 Jul 1;182(3):517-21 

Correlation between internal motion and emission kinetics of tryptophan residues
in proteins.

Kouyama T, Kinosita K Jr, Ikegami A.

Institute of Physical and Chemical Research, Saitama, Japan.

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.

PMID: 2753033 [PubMed - indexed for MEDLINE]