  Samples suitable for electron diffraction studies must satisfy certain
characteristics such as having a thickness in the range of 10 - 100 nm. We
report, to our knowledge, the first successful synthesis technique of
nanometer-thin sheets of single-crystalline thymine suitable for electron
diffraction and spectroscopy studies. This development provides a well defined
system to explore issues related to UV photochemistry of DNA and high intrinsic
stability essential to maintaining integrity of genetic information. The
crystals are grown using the evaporation technique and the nanometer-thin
sheets are obtained via microtoming. The sample is characterized via x-ray
diffraction (XRD) and is subsequently studied using electron diffraction via a
transmission electron microscope (TEM). Thymine is found to be more radiation
resistant than similar molecular moieties (e.g., carbamazepine) by a factor of
5. This raises interesting questions about the role of the fast relaxation
processes of electron scattering-induced excited states, extending the concept
of radiation hardening beyond photoexcited states. The high stability of
thymine in particular opens the door for further studies of these ultrafast
relaxation processes giving rise to the high stability of DNA to UV radiation.
