1: Biochemistry  1983 Dec 6;22(25):6018-26 

Internal motion of deoxyribonucleic acid in chromatin. Nanosecond fluorescence
studies of intercalated ethidium.

Ashikawa I, Kinosita K Jr, Ikegami A, Nishimura Y, Tsuboi M, Watanabe K, Iso K,
Nakano T.

We have investigated the internal motions of DNA in a nucleosome core particle
and chromatin by measuring the nanosecond fluorescence depolarization of
intercalated ethidium. Assuming that the observed anisotrophy decay originates
from the torsional motion of DNA, we have analyzed the dynamics of DNA in a
nucleosome core particle and in chromatin in detail. The results suggest that
DNA in a nucleosome core particle has a torsional rigidity similar to that of
DNA in solution and that even at the point of the ionic bonds between DNA and a
histone octamer the torsional motion of DNA is not completely inhibited. On the
other hand, the dynamics of linker DNA in chromatin were found to reflect the
overall structural state of the chromatin: the motion of linker DNA was
suppressed as the structure of chromatin turned from an extended state to a
condensed one. This indicates that, in solenoidal chromatin, nucleosome
movements in chromatin are largely suppressed. Furthermore, the result may
suggest that the torsional rigidity of linker DNA is increased as it is forced
to bend in solenoidal chromatin.

PMID: 6661423 [PubMed - indexed for MEDLINE]