Direct imaging of single DNA molecules

Although the structure of DNA was first determined in 1953,1 there have since been several unsuccessful attempts to obtain a direct image of the structure. With such direct images, quantitative evaluation of the molecule's characteristic dimensions would be possible. Direct images of DNA, however, are difficult to obtain for two main reasons. First, the elements that form the molecule intrinsically have very low contrast. In addition, preparing the DNA sample for imaging is hard to achieve while also preserving its pristine shape and size.