Book of Abstracts: Albany 2009

category image Albany 2009
Conversation 16
June 16-20 2009
© Adenine Press (2008)

Different Modes of Hoechst 33258 Binding with Different GC-content DNAs

The thermal stability of different GC-content DNA double helixes (ds-DNA) in the presence of Hoechst 33258 (H33258) was investigated using thermal denaturation monitored by UV absorbance. It was found that the H33258 displayed a marked effect on thermal stability of ds-DNA: melting temperature (Tm) of the ligand-DNA complexes are greater than that of naked DNA. H33258 is well-known to have a primary preference for A/T stretches suggesting that the width of the helix-coil transition for DNA in the absence of the ligand 0T) must be greater than that for complexes (Δ T). Our experimental results show that the dependences of δ( Δ T/Tm2)= ΔT/Tm20T/T02 on ligand to nucleotides molar ratios (rb) for the complexes of H33258 with Cl. perfr. (31% of GC content) and for M.lysod. (72% of GC content) coincide very closely at μμ=2 mM Na+. This result suggests that the minor groove structure and hydration which play the dominant role for optimization of van der Waals? contacts and hydrogen bonding for the ligand interaction with DNA are quite different from the preferential binding sites for the ligand at low ionic strength. The binding preference of H33258 for AT-rich regions of ds-DNA becomes obvious when the salt concentration increases μ>10mM Na+. The dependences of δ(ΔT/Tm2) on rb become negative expressing the AT specificity of the ligand. The great difference in the shape of dependences of δ (ΔT/Tm2) at low (μ=2 mM Na+) and high (μ=20 mM Na+) demonstrate the influence of environment, detailed nature of binding sites and different hydration of the minor groove of different GC-content DNAs playing an important role in ligand interaction (1,2).

References and Footnotes
  1. S.Y.Breusogen et al. JMB, 315, 1049-1061 (2002)
  2. A.N. Lane and T.C. Jenkins Quar.Revews of Biophysics, 33, 255-306 (2000).

Poghos O.Vardevanyan*
Ara P. Antonyan
Ruzanna A. Karapetian
Marine A. Parsadanyan
Mariam A. Shahinyan

Dept. of Biophysics
Yerevan State Univeristy
Yerevan 0025, Armenia