JILA scientists have developed a fast, simple sample preparation method that enhances imaging of DNA to better analyze its physical properties and interactions. This gentle yet effective process involves binding DNA to mica, a flat silicate mineral. This process extends the DNA's configuration – similar to expanding the bellows of an accordion – so that eight times more of the molecule can be analyzed as compared to previous methods.
Atomic Force Microscopy (AFM) imaging of the extended structures in liquid improved the quality and quantity of biophysical data on DNA and its interactions with proteins. The method produced high-quality images over a wide range of salt concentrations, including ones similar to those found in a cell. This was previously thought impossible because different salts ordinarily compete to attach the DNA to the surface or interfere with that attachment. High-resolution images revealed the DNA's iconic double helix structure, which looks like a twisted ladder.
JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder. "We expect this new sample preparation method to pave the way to tuning the binding strength of DNA to a surface, which should facilitate studying the dynamics of protein-DNA complexes," said NIST/JILA Fellow Tom Perkins.