Tautomerization of Thymine Using Ultraviolet Light.

Area of Science:

• Surface Science
• Photochemistry
• Computational Chemistry

Background:

• Ultraviolet (UV) radiation can induce significant alterations in biological molecules.
• Understanding molecular changes on surfaces is crucial for various applications.
• Thymine is a fundamental DNA nucleobase susceptible to UV damage.

Purpose of the Study:

• To investigate UV-light-induced structural changes in thymine on a molybdenum disulfide (MoS2) surface.
• To elucidate the interaction mechanisms between thymine and MoS2 under UV irradiation.
• To explore alternative photoproduct pathways beyond dimerization.

Main Methods:

• Photoelectron spectroscopy was employed to probe core electron binding energies.
• First-principles calculations, specifically coupled cluster singles and doubles (CCSD) linear response theory, were used for theoretical interpretation.
• Ab initio methods provided insights into the observed molecular transformations.

Main Results:

• UV exposure induced a shift between tautomeric forms of thymine on the MoS2 surface.
• Contrary to expectations, thymine dimerization into pyrimidine dimers was not the primary observed outcome.
• Changes in core electron binding energies indicated significant structural modifications.

Conclusions:

• The MoS2 surface influences the UV-induced photochemistry of thymine.
• A tautomeric shift is a key photoreaction pathway for thymine on MoS2, differing from typical solution-phase behavior.
• This study provides a deeper understanding of UV damage mechanisms and suggests ways to mitigate harmful photoproduct formation.