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Steroid diamine-nucleic acid interactions: partial insertion of dipyrandium between unstacked base pairs of the poly(dA-dT) duplex in solution

Steroid diamine-nucleic acid interactions: partial insertion of dipyrandium between unstacked... We report on an NMR investigation of steroid diamine.nucleic acid complexes as a function of phosphate-to-drug ratios in aqueous solution in order to evaluate the structural and kinetic aspects of the binding of a nonintercalative drug to a synthetic DNA in solution. The nonexchangeable proton chemical shift parameters for the dipyrandium.poly(dA-dT) complex demonstrate unstacking of base pairs and partial insertion of the steroid diamine at the complexation site. The chemical shifts and linewidths of the exchangeable protons as a function of pH demonstrate that the base pairs are intact but partially exposed to solvent at the steroid diamine binding site. The phosphorus chemical shifts suggest that the base pairs unstack upon complex formation without changes in the omega,omega' polynucleotide backbone torsion angles. The NMR line shape parameters require rapid exchange of the steroid diamine among potential binding sites and are consistent with greater segmental flexibility in the complex compared to the synthetic DNA in solution. The NMR experiments are discussed in relation to Sobell's proposed model Sobell, H.M., Tsai, C.C., Gilbert, S.G., Jain, S.C. & Sakore, T.D. (1976) Proc. Natl. Acad. Sci USA 73, 3068-3072 for the steroid diamine-DNA complex. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Proceedings of the National Academy of Sciences PNAS

Steroid diamine-nucleic acid interactions: partial insertion of dipyrandium between unstacked base pairs of the poly(dA-dT) duplex in solution

Steroid diamine-nucleic acid interactions: partial insertion of dipyrandium between unstacked base pairs of the poly(dA-dT) duplex in solution

Proceedings of the National Academy of Sciences , Volume 76 (1): 24 – Jan 1, 1979

Abstract

We report on an NMR investigation of steroid diamine.nucleic acid complexes as a function of phosphate-to-drug ratios in aqueous solution in order to evaluate the structural and kinetic aspects of the binding of a nonintercalative drug to a synthetic DNA in solution. The nonexchangeable proton chemical shift parameters for the dipyrandium.poly(dA-dT) complex demonstrate unstacking of base pairs and partial insertion of the steroid diamine at the complexation site. The chemical shifts and linewidths of the exchangeable protons as a function of pH demonstrate that the base pairs are intact but partially exposed to solvent at the steroid diamine binding site. The phosphorus chemical shifts suggest that the base pairs unstack upon complex formation without changes in the omega,omega' polynucleotide backbone torsion angles. The NMR line shape parameters require rapid exchange of the steroid diamine among potential binding sites and are consistent with greater segmental flexibility in the complex compared to the synthetic DNA in solution. The NMR experiments are discussed in relation to Sobell's proposed model Sobell, H.M., Tsai, C.C., Gilbert, S.G., Jain, S.C. & Sakore, T.D. (1976) Proc. Natl. Acad. Sci USA 73, 3068-3072 for the steroid diamine-DNA complex.

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Publisher
PNAS
Copyright
Copyright ©2009 by the National Academy of Sciences
ISSN
0027-8424
eISSN
1091-6490
Publisher site
See Article on Publisher Site

Abstract

We report on an NMR investigation of steroid diamine.nucleic acid complexes as a function of phosphate-to-drug ratios in aqueous solution in order to evaluate the structural and kinetic aspects of the binding of a nonintercalative drug to a synthetic DNA in solution. The nonexchangeable proton chemical shift parameters for the dipyrandium.poly(dA-dT) complex demonstrate unstacking of base pairs and partial insertion of the steroid diamine at the complexation site. The chemical shifts and linewidths of the exchangeable protons as a function of pH demonstrate that the base pairs are intact but partially exposed to solvent at the steroid diamine binding site. The phosphorus chemical shifts suggest that the base pairs unstack upon complex formation without changes in the omega,omega' polynucleotide backbone torsion angles. The NMR line shape parameters require rapid exchange of the steroid diamine among potential binding sites and are consistent with greater segmental flexibility in the complex compared to the synthetic DNA in solution. The NMR experiments are discussed in relation to Sobell's proposed model Sobell, H.M., Tsai, C.C., Gilbert, S.G., Jain, S.C. & Sakore, T.D. (1976) Proc. Natl. Acad. Sci USA 73, 3068-3072 for the steroid diamine-DNA complex.

Journal

Proceedings of the National Academy of SciencesPNAS

Published: Jan 1, 1979

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