Nucleic Acids Research, Vol 25, Issue 22 4523-4531, Copyright © 1997 by Oxford University Press
DB Davies, VI Pahomov and AN Veselkov
1D and 2D NMR spectroscopy (500/600 MHz) has been used to investigate the
equilibrium conformational states of the deoxyheptanucleotide 5'-
d(GpCpGpApApGpC), as well as its complexation with the phenanthridinium
drug ethidium bromide (EB). Quantitative determination (reaction constants
and thermodynamic parameters) of the conformational equilibrium of the
heptamer in solution and its complexation with EB was based on analysis of
the dependence of proton chemical shifts on concentration (at two
temperatures, 298 and 308 K) and on temperature (in the range 278-353 K).
The experimental results were analysed in terms of a model of the dynamic
equilibrium between single-stranded, hairpin and bulged dimer forms of the
deoxyheptanucleotide and its complexes with EB. Calculation of the relative
amounts of the different complexes reveals important features of the
dynamic equilibrium as a function of both temperature and the ratio of the
drug and heptamer concentrations. The quantitative analysis also provides
the limiting proton chemical shifts of EB in each complex which have been
used to determine the most favourable structures of the intercalated
complexes of EB with the (GC) sites of both the hairpin and dimer forms of
the heptanucleotide.
ARTICLES
NMR determination of the conformational and drug binding properties of the DNA heptamer d(GpCpGpApApGpC) in aqueous solution
Department of Chemistry, Birkbeck College, University of London, Gordon House, 29 Gordon Square, London WC1H OPP, UK.
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