Unraveling the structure of DNA during overstretching by using multicolor, single-molecule fluorescence imaging.

ABSTRACT: Single-molecule manipulation studies have revealed that double-stranded DNA undergoes a structural transition when subjected to tension. At forces that depend on the attachment geometry of the DNA (65 pN or 110 pN), it elongates approximately 1.7-fold and its elastic properties change dramatically. The nature of this overstretched DNA has been under debate. In one model, the DNA cooperatively unwinds, while base pairing remains intact. In a competing model, the hydrogen bonds between base pairs break and two single DNA strands are formed, comparable to thermal DNA melting. Here, we resolve the structural basis of DNA overstretching using a combination of fluorescence microscopy, optical tweezers, and microfluidics. In DNA molecules undergoing the transition, we visualize double- and single

SUBMITTER: van Mameren J 

PROVIDER: S-EPMC2775282 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature