2thiocytosine

2-thiocytosine is a thiocarbonyl analog of the DNA and RNA nucleobase cytosine. In 2-thiocytosine, the oxygen atom at the C2 position of cytosine is replaced by a sulfur atom. This modification significantly alters its chemical properties, including its tautomeric preferences and hydrogen bonding capabilities.

2-thiocytosine can exist in different tautomeric forms, primarily the thiolactam and thioenol forms. The thiolactam form is generally more stable. Its base pairing properties are altered compared to cytosine. While it can still form hydrogen bonds, the presence of sulfur influences the strength and geometry of these interactions, which can have implications for DNA and RNA structure and function.

This modified nucleobase has found applications in various fields. In molecular biology and biophysics, it is used as a probe to study DNA and RNA structure, protein-nucleic acid interactions, and to investigate the effects of base modifications on nucleic acid properties. The unique spectroscopic characteristics of the thiocarbonyl group can also be exploited for analytical purposes, such as in fluorescence studies or as part of spectroscopic labels. Furthermore, 2-thiocytosine and its derivatives have been explored for their potential therapeutic applications, including in the development of antiviral and anticancer agents, due to their ability to interfere with nucleic acid metabolism or function.