title: Stretching chimeric DNA: a test for the putative S-form.
abstract: Double-stranded DNA "overstretches" at a pulling force of about 65 pN, increasing in length by a factor of 1.7. The nature of the overstretched state is unknown, despite its considerable importance for DNA's biological function and technological application. Overstretching is thought by some to be a force-induced denaturation and by others to consist of a transition to an elongated, hybridized state called S-DNA. Within a statistical mechanical model, we consider the effect upon overstretching of extreme sequence heterogeneity. "Chimeric" sequences possessing halves of markedly different AT composition elongate under fixed external conditions via distinct, spatially segregated transitions. The corresponding force-extension data vary with pulling rate in a manner that depends qualitatively and strikingly upon whether the hybridized S-form is accessible. This observation implies a test for S-DNA that could be performed in experiment.
authors.affiliation: Systems Biology Centre, University of Warwick, Coventry, United Kingdom. swhitelam@lbl.gov
authors.forename: Stephen
authors.initials: S
authors.lastname: Whitelam
authors.forename: Sander
authors.initials: S
authors.lastname: Pronk
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Geissler
mesh_terms: D020029:Base Pairing; D001696:Biomechanical Phenomena; D004247:DNA / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D013696:Temperature
chemical_list: D004247:DNA