title: Mechanical properties of high-G.C content DNA with a-type base-stacking.
abstract: 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.
authors.affiliation: Instituto Madrileño de Estudios Avanzados en Nanociencia, Madrid, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Hormeño
authors.forename: Borja
authors.initials: B
authors.lastname: Ibarra
authors.forename: José L
authors.initials: JL
authors.lastname: Carrascosa
authors.forename: José M
authors.initials: JM
authors.lastname: Valpuesta
authors.forename: Fernando
authors.initials: F
authors.lastname: Moreno-Herrero
authors.forename: J Ricardo
authors.initials: JR
authors.lastname: Arias-Gonzalez
mesh_terms: D001482:Base Composition; D020029:Base Pairing; D001696:Biomechanical Phenomena; D044704:DNA, A-Form / Q000737:chemistry*; D004269:DNA, Bacterial / Q000737:chemistry; D004548:Elasticity; D008280:Magnetics; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D052898:Optical Tweezers; D013302:Streptomyces
chemical_list: D044704:DNA, A-Form; D004269:DNA, Bacterial