  Low-energy electrons offer a unique possibility for long exposure imaging of
individual biomolecules without significant radiation damage. In addition,
low-energy electrons exhibit high sensitivity to local potentials and thus can
be employed for imaging charges as small as a fraction of one elementary
charge. The combination of these properties makes low-energy electrons an
exciting tool for imaging charge transport in individual biomolecules. Here we
demonstrate the imaging of individual deoxyribonucleic acid (DNA) molecules at
the resolution of about 1 nm with simultaneous imaging of the charging of the
DNA molecules that is of the order of less than one elementary charge per
nanometer. The cross-correlation analysis performed on different sections of
the DNA network reveals that the charge redistribution between the two regions
is correlated. Thus, low-energy electron microscopy is capable to provide
simultaneous imaging of macromolecular structure and its charge distribution
which can be beneficial for imaging and constructing nano-bio-sensors.
