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Harmonic dynamics of a DNA hexamer in the absence and presence of the intercalator ethidium
Author(s) -
Rudolph Barbara R.,
Case David A.
Publication year - 1989
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360280406
Subject(s) - intercalation (chemistry) , chemistry , base pair , dna , crystallography , cytosine , ethidium bromide , random hexamer , stereochemistry , biophysics , biochemistry , inorganic chemistry , biology
Vibrational normal mode calculations are presented for a DNA hexanucleoside pentaphosphate, d(CpGpCpGpCpG) 2 , and for its complex with the cationic interclator ethidium. Two intercalation sites are modeled that differ in DNA backbone torsion angles. Normal mode frequencies for the DNA fragment itself are significantly lower than those reported earlier using different force fields, but an analysis of “effective” frequencies suggests that somewhat higher frequencies are more appropriate. Intercalation leads to significant lowering of mobility for the base pairs adjacent to the drug; in this sequence, the ethidium binding affects the guanosine atoms more strongly than the cytosine atoms. Motions of the bases and the intercalator are analyzed in terms of “twist” about the local helix axis and a “tilt” angle relative to this axis, and the results are compared to fluorescence studies of ethidium‐DNA complexes.