Well-defined and sequence-specific noncovalent binding forces of DNA.

The specific binding between the two DNA strands in a double helix is one of the most fundamental and influential molecular interactions in biochemistry. Using force-induced remnant magnetization spectroscopy (FIRMS), we obtained well-defined binding forces of DNA oligomers, with a narrow force distribution of 1.8 pN. The narrow force distribution allows for directly resolving two DNA duplexes with a single base-pair difference in the same sample. Therefore, binding force can serve as a discriminating parameter for probing different DNA interactions. Furthermore, we observed that the binding forces depend on the position of the mismatching base pair. Our results show that FIRMS is capable of high-precision mechanical measurements of biochemical processes involving multiple DNA interactions and has the potential for characterizing the binding strength of materials based on DNA origami.