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Force-induced melting of DNA-evidence for peeling and internal melting from force spectra on short synthetic duplex sequences

Niklas Bosaeus (Institutionen för kemi- och bioteknik, Fysikalisk kemi) ; A. H. El-Sagheer ; T. Brown ; Björn Åkerman (Institutionen för kemi- och bioteknik, Fysikalisk kemi) ; Bengt Nordén (Institutionen för kemi- och bioteknik, Fysikalisk kemi)
Nucleic Acids Research (0305-1048). Vol. 42 (2014), 12, p. 8083-8091.
[Artikel, refereegranskad vetenskaplig]

Overstretching of DNA occurs at about 60-70 pN when a torsionally unconstrained double-stranded DNA molecule is stretched by its ends. During the transition, the contour length increases by up to 70% without complete strand dissociation. Three mechanisms are thought to be involved: force-induced melting into single-stranded DNA where either one or both strands carry the tension, or a B-to-S transition into a longer, still base-paired conformation. We stretch sequence-designed oligonucleotides in an effort to isolate the three processes, focusing on force-induced melting. By introducing site-specific inter-strand cross-links in one or both ends of a 64 bp AT-rich duplex we could repeatedly follow the two melting processes at 5 mM and 1 M monovalent salt. We find that when one end is sealed the AT-rich sequence undergoes peeling exhibiting hysteresis at low and high salt. When both ends are sealed the AT sequence instead undergoes internal melting. Thirdly, the peeling melting is studied in a composite oligonucleotide where the same AT-rich sequence is concatenated to a GC-rich sequence known to undergo a B-to-S transition rather than melting. The construct then first melts in the AT-rich part followed at higher forces by a B-to-S transition in the GC-part, indicating that DNA overstretching modes are additive.



Denna post skapades 2014-09-03. Senast ändrad 2015-03-30.
CPL Pubid: 202305

 

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Institutioner (Chalmers)

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

Ämnesområden

Fysikalisk kemi

Chalmers infrastruktur