Helical periodicity of DNA determined by enzyme digestion.

The periodicity of DNA has been determined by binding short, stiff pieces of DNA to a flat surface and using DNase I to probe the accessibility of the phosphodiester bonds. We have found that the distance between successive DNase I cutting sites is 10.6 +/- 0.1 bases for the DNA immobilized on three different surfaces. We identify this value with the number of base pairs per turn of the DNA double helix in solution.