Direct measurements of base stacking interactions in DNA by single-molecule atomic-force spectroscopy.
We investigate the elasticity of two types of single-stranded synthetic DNA homopolydeoxynucletides, poly(dA) and poly(dT), by AFM-based single-molecule force spectroscopy. We find that poly(dT) exhibits the expected entropic elasticity behavior, while poly(dA) unexpectedly displays two overstretching transitions in the force-extension relationship. We suggest that these transitions, which occur at approximately 23 pN and approximately 113 pN, directly capture, for the first time, the mechanical signature of base-stacking interactions among adenines in DNA, in the absence of base pairing.
Department of Mechanical Engineering and Materials Science, Center for Biologically Inspired Materials and Material Systems, Duke University, Durham, North Carolina, USA.
Changhong
C
Ke
Michael
M
Humeniuk
Hanna
H
S-Gracz
Piotr E
PE
Marszalek
D020029:Base Pairing; D004247:DNA / Q000737:chemistry* / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force; D011089:Polydeoxyribonucleotides / Q000737:chemistry
D011089:Polydeoxyribonucleotides; D004247:DNA