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Tension induces a base-paired overstretched DNA conformation

Niklas Bosaeus (Institutionen för kemi- och bioteknik, Fysikalisk kemi) ; A. H. El-Sagheer ; T. Brown ; S. B. Smith ; Björn Åkerman (Institutionen för kemi- och bioteknik, Fysikalisk kemi) ; C. Bustamante ; Bengt Nordén (Institutionen för kemi- och bioteknik, Fysikalisk kemi)
Proceedings of the National Academy of Sciences of the United States of America (0027-8424). Vol. 109 (2012), 38, p. 15179-15184.
[Artikel, refereegranskad vetenskaplig]

Mixed-sequence DNA molecules undergo mechanical overstretching by approximately 70% at 60-70 pN. Since its initial discovery 15 y ago, a debate has arisen as to whether the molecule adopts a new form [Cluzel P, et al. (1996) Science 271: 792-794; Smith SB, Cui Y, Bustamante C (1996) Science 271: 795-799], or simply denatures under tension [van Mameren J, et al. (2009) Proc Natl Acad Sci USA 106: 18231-18236]. Here, we resolve this controversy by using optical tweezers to extend small 60-64 bp single DNA duplex molecules whose base content can be designed at will. We show that when AT content is high (70%), a force-induced denaturation of the DNA helix ensues at 62 pN that is accompanied by an extension of the molecule of approximately 70%. By contrast, GC-rich sequences (60% GC) are found to undergo a reversible overstretching transition into a distinct form that is characterized by a 51% extension and that remains base-paired. For the first time, results proving the existence of a stretched basepaired form of DNA can be presented. The extension observed in the reversible transition coincides with that produced on DNA by binding of bacterial RecA and human Rad51, pointing to its possible relevance in homologous recombination.

Nyckelord: elongated DNA, mechanical properties of DNA, mechanism of recombination, single molecule, DNA stretching, double helix, structural transitions, terminal alkynes, linear, dichroism, stranded-dna, molecule, force, complexes, acid, thermodynamics

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Denna post skapades 2012-11-07. Senast ändrad 2015-03-30.
CPL Pubid: 165605


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Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Fysikalisk kemi (2005-2014)


Nanovetenskap och nanoteknik

Chalmers infrastruktur

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