- C. Ke and M. Humeniuk and H. S-gracz and P. E. Marszalek, Direct measurements of base stacking interactions in DNA by single-molecule atomic-force spectroscopy,
Physical Review Letters, vol. 99 no. 1
(July, 2007) .
(last updated on 2009/08/04)
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 similar to 23 pN and similar to 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.