Mechanical Properties of High-G⋅C Content DNA with A-Type Base-Stacking
2011
Hormeño, Silvia | Ibarra, Borja | Carrascosa, José L. | Valpuesta, José M. | Moreno-Herrero, Fernando | Arias-Gonzalez, J Ricardo
The sequence of a DNA molecule is known to influence its secondary structure and flexibility. Using a combination of bulk and single-molecule techniques, we measure the structural and mechanical properties of two DNAs which differ in both sequence and base-stacking arrangement in aqueous buffer, as revealed by circular dichroism: one with 50% G·C content and B-form and the other with 70% G·C content and A-form. Atomic force microscopy measurements reveal that the local A-form structure of the high-G·C DNA does not lead to a global contour-length decrease with respect to that of the molecule in B-form although it affects its persistence length. In the presence of force, however, the stiffness of high-G·C content DNA is similar to that of balanced-G·C DNA as magnetic and optical tweezers measured typical values for the persistence length of both DNA substrates. This indicates that sequence-induced local distortions from the B-form are compromised under tension. Finally, high-G·C DNA is significantly harder to stretch than 50%-G·C DNA as manifested by a larger stretch modulus. Our results show that a local, basepair configuration of DNA induced by high-G·C content influences the stretching elasticity of the polymer but that it does not affect the global, double-helix arrangement.
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