Evidence for an increase of DNA contour length at low ionic strength.

AUTOR(ES)

Geller, K

RESUMO

The polyion chain expansion of DNA was studied by viscometry within the Na+ concentration range c5 = 0.002 M to 0.4 M. The DNA molecular weights M were between 0.5 x 10(6) and 13 x 10(6). The relative change of intrinsic viscosity [eta] is linearly correlated to c5(-1/2) with a slope that increases with increasing M. This behaviour reflects the predominance of helix stiffening in chain expansion. At c5(112) > 0.01(-1/2 M-1/2 (Debye-Hückel screening radius 1/chi > (1/chi)*=3nm) the relative change of [eta] rises with a steeper slope. This effect increases with decreasing M suggesting that helix lengthening contributes to the chain expansion. Our model enables us to interpret other ionic-strength dependent effects known from literature. The start of the significant duplex elongation at (1/chi)* can be correlated to the polyion-charge arrangement. In accordance with our interpretation (1/chi)* is found to be greater for DNA-intercalator complexes.

Documentos Relacionados

• Evidence for cross-bridge attachment in relaxed muscle at low ionic strength.
• The roles of H1, the histone core and DNA length in the unfolding of nucleosomes at low ionic strength.
• The interaction of ethidium with synthetic double-stranded polynucleotides at low ionic strength.
• On the de novo formation of compact oligonucleosomes at high ionic strength. Evidence for nucleosomal sliding in high salt.
• Stabilization of Z-DNA by polyarginine near physiological ionic strength.