Scanning force microscopy of circular DNA and chromatin in air and propanol

High resolution electron micrographs of microtips show nanometer surface irregularities. We propose that the lower contact forces, and consequent greater sensitivity, from imaging in propanol enables small biomolecules to be imaged at higher resolution by these 'nanotips'. However, larger molecules, such as the nucleosomes of chromatin, are still imaged by the bulk of the tip and no improvement of resolution is obtained.