title: Direct observation of multiple pathways of single-stranded DNA stretching.
abstract: We observed multiple pathways of stretching single-stranded polydeoxynucleotides, poly(dA). Poly(dA) has been shown to undergo unique transitions under mechanical force, and such transitions were attributed to the stacking characteristics of poly(dA). Using single-molecule manipulation studies, we found that poly(dA) has two stretching pathways at high forces. The previously observed pathway has a free energy that is less than what is expected of single-stranded DNA with a random sequence, indicating the existence of a novel conformation of poly(dA) at large extensions. We also observed stepwise transitions between the two pathways by pulling the molecule with constant force, and found that the transitions are cooperative. These results suggest that the unique mechanical property of poly(dA) may play an important role in biological processes such as gene expression.
authors.affiliation: Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA.
authors.forename: Wuen-Shiu
authors.initials: WS
authors.lastname: Chen
authors.forename: Wei-Hung
authors.initials: WH
authors.lastname: Chen
authors.forename: Zephan
authors.initials: Z
authors.lastname: Chen
authors.forename: Ashton A
authors.initials: AA
authors.lastname: Gooding
authors.forename: Kuan-Jiuh
authors.initials: KJ
authors.lastname: Lin
authors.forename: Ching-Hwa
authors.initials: CH
authors.lastname: Kiang
mesh_terms: D000225:Adenine / Q000737:chemistry; D001696:Biomechanical Phenomena; D004277:DNA, Single-Stranded / Q000737:chemistry*; D009690:Nucleic Acid Conformation
chemical_list: D004277:DNA, Single-Stranded; D000225:Adenine