RT Journal Article
SR Electronic
T1 Overstretching B-DNA: The Elastic Response of Individual Double-Stranded and Single-Stranded DNA Molecules
JF Science
JO Science
FD American Association for the Advancement of Science
SP 795
OP 799
DO 10.1126/science.271.5250.795
VO 271
IS 5250
A1 Smith, Steven B.
A1 Cui, Yujia
A1 Bustamante, Carlos
YR 1996
UL http://science.sciencemag.org/content/271/5250/795.abstract
AB Single molecules of double-stranded DNA (dsDNA) were stretched with force-measuring laser tweezers. Under a longitudinal stress of ∼65 piconewtons (pN), dsDNA molecules in aqueous buffer undergo a highly cooperative transition into a stable form with 5.8 angstroms rise per base pair, that is, 70% longer than B-form dsDNA. When the stress was relaxed below 65 pN, the molecules rapidly and reversibly contracted to their normal contour lengths. This transition was affected by changes in the ionic strength of the medium and the water activity or by cross-linking of the two strands of dsDNA. Individual molecules of single-stranded DNA were also stretched giving a persistence length of 7.5 angstroms and a stretch modulus of 800 pN. The overstretched form may play a significant role in the energetics of DNA recombination.