Principles of Fluorescence Spectroscopy

PRINCIPLES OF FLUORESCENCE SPECTROSCOPY 405
Figure 11.31. Tryptophan correlation time distributions for HIV-1 integrase in the presence of a 21-base-pair DNA oligomer [integrase] = 100 nM.
Proposed structures are shown for the monomer and tetramer. N-terminal domain is red, catalytic core domain is green, and the C-terminal domain is
blue. Revised from [98–99]. Structure courtesy of Dr. Alexei Podtelezhnikov from the University of California at San Diego.
study the self-association of integrase monomers. 98 Figure
11.31 shows the recovered correlation time distribution for
integrase in the absence of DNA substrate. The correlation
time near 2–3 ns was assigned to the local dynamics of integrase
and not linked to its extent of association. The longer
correlation times centered near 100 ns were interpreted as
due to the integrase tetramer. The distribution of the long
correlation time is wide because this value is uncertain due
to the short lifetime of tryptophan. The large difference
between the lifetime and correlation time results in the wide
amplitude at times above 80 ns which are not determined by
the data.