Nanomechanics of Poly Nucleic Acids Probed with AFM Based Force Spectroscopy
We use AFM-based single-molecule force spectroscopy to, for the first time, compare and contrast the elasticity of different sequences of double and single stranded polynucleotides, including single stranded poly(A), poly(dA), poly(dT), poly(C), and poly(dC); and double stranded poly(dA)poly(dT), poly(dA-dT), poly(dG)poly(dC), and poly(dG-dC). We found that even up to forces as high as 800 pN poly(dA) is stiffer than the other single stranded structures. We have also observed marked differences in the behavior of double stranded poly(dA)poly(dT) and poly(dG)poly(dC) with poly(dA-dT) and poly(dG-dC), respectively. Despite their different elasticities, these double stranded polynucleotides exhibit striking features similar to those exhibited by poly(dA) when stretched.
We investigate the origin of these differences and similarities in terms of base-base and base-backbone interactions.