Synthesis technique and electron beam damage study of nanometer-thin single-crystalline Thymine

TL;DR

This paper presents a novel synthesis method for nanometer-thin single-crystalline thymine sheets suitable for electron diffraction, revealing thymine's high radiation resistance and potential for studying DNA UV stability.

Contribution

First successful synthesis of nanometer-thin single-crystalline thymine sheets for electron diffraction and spectroscopy studies, enabling new insights into DNA UV photochemistry and stability.

Findings

Thymine sheets are more radiation resistant than similar molecules.

Thymine's stability suggests ultrafast relaxation processes.

Potential for studying DNA UV damage mechanisms.

Abstract

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.