We report an apparent linear correlation between the entropy and the volume change for the association of the minor groove ligand, distamycin A, to synthetic polynucleotides of known sequence. The slope of the fitted line, ΔS°/ΔV°, is significantly more shallow than that reported for the protonation of small organic acids and reflects, therefore, a smaller compression of the water dipoles arrayed as spine in the minor groove of the double helix prior to the release into the solvent during the binding process. The amount of releasable spine water is believed to be a function of the DNA sequence, thus giving rise to the observed linear correlation because other entropic effects appear nearly identical for these polynucleotides tested.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry