Transition dynamics and selection of the distinct S-DNA and strand unpeeling modes of double helix overstretching.

ABSTRACT: Recent studies have revealed two distinct pathways for the DNA overstretching transition near 65 pN: 'unpeeling' of one strand from the other, and a transition from B-DNA to an elongated double-stranded 'S-DNA' form. However, basic questions concerning the dynamics of these transitions, relative stability of the two competing overstretched states, and effects of nicks and free DNA ends on overstretching, remain open. In this study we report that: (i) stepwise extension changes caused by sequence-defined barriers occur during the strand-unpeeling transition, whereas rapid, sequence-independent extension fluctuations occur during the B to S transition; (ii) the secondary transition that often occurs following the overstretching transition is strand-unpeeling, during which the extension incre

SUBMITTER: Fu H 

PROVIDER: S-EPMC3082884 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature