Methylene blue binding to DNA with alternating GC base sequence: Continuum treatment of salt effects

Item Type:	Article
Title:	Methylene blue binding to DNA with alternating GC base sequence: Continuum treatment of salt effects
Creators Name:	Rohs, R. and Sklenar, H.
Abstract:	Methylene blue (MB), an efficient singlet oxygen generating photoactive dye, binds to DNA and allows photosensitized reactions to be used for sequence-specific cleavage of the DNA backbone. Intercalation and groove binding are possible binding modes of the dye, depending on base sequences and environmental conditions. In a recent modeling study of methylene blue binding to a double stranded DNA decamer with an alternating GC sequence, six structural models for intercalation structures and for minor and major groove binding have been obtained. By estimating the binding energies (including electrostatic reaction field contributions of a salt-free aqueous solvent), symmetric intercalation at the 5′-CpG-3′ and 5′-GpC-3′ steps was found as the predominant binding mode, followed by a slightly weaker binding of the dye in the minor groove. In this study, the stability of the modeled structures has been analysed as a function of salt concentration. The results of finite difference numerical solutions of the non-linear Poisson-Boltzmann equation show that the stabilizing effect of salt is larger for free DNA than for the modeled MB-DNA complexes. Accordingly, the estimated binding energies decrease with increasing ionic strength. A slightly higher stabilization of the groove binding complexes results in comparable binding energies for symmetric intercalation and minor groove binding at high salt concentration. Both results are in qualitative agreement with experimental data.
Keywords:	CpG Islands, Cytosine, DNA, Enzyme Inhibitors, Guanine, Kinetics, Methylene Blue, Molecular Models, Nucleic Acid Conformation, Oxygen, Salts, Statistical Models, Thermodynamics
Source:	Indian Journal of Biochemistry & Biophysics
ISSN:	0301-1208
Publisher:	Natl Inst Science Communication
Volume:	38
Number:	1-2
Page Range:	1-6
Date:	1 January 2001
PubMed:	View item in PubMed

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