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The research results of Ms. Wawa Sato (Graduate School of Science and Engineering, 2nd year, Master's course in Chemistry, Department of Science and Engineering, at the time of publication) in the Laser Photochemistry Laboratory (Prof. Tadashi Suzuki) have been published in the journal "Photochemistry and Photobiology" of the American Society for Photobiology, Photochem. Photochemistry and Photobiology", a journal of the American Photobiological Society.

Research overview

Cells contain a substance called nucleic acid. You may have heard the terms DNA and RNA in the news. These are nucleic acids. DNA plays an important role in storing genetic information and copying (transcribes) that information to RNA in order to make proteins. The main substances that make up DNA are nucleic acid bases. There are only five types of nucleic acid bases: adenine, thymine, guanine, cytosine, and uracil (Figure 1). New properties can be given to nucleic acid bases by chemical modification. For example, 5-fluorouracil, a substance in which one hydrogen atom in uracil is replaced with a fluorine atom (F), has anti-cancer properties and is actually used in medicine as an anti-cancer drug. In addition to these, many other nucleic acids and modified nucleic acids (nucleic acid bases) with medicinal properties are known.

The target molecule is a thionucleic acid base called 5-fluoro-4-thiouracil. This is a thionucleic acid base in which a sulfur atom (S) has been added to 5-fluorouracil, which is also used as an anticancer drug. Nucleic acid bases containing a thiocarbonyl group are called thionucleic acid bases. Unlike ordinary thionucleic acid bases, thionucleic acid bases are known to absorb ultraviolet light (UVA light) and induce cell death. We are conducting research to see if this unique property can be applied to use as a drug in photodynamic therapy (Figure 2) for cancer treatment.

Using laser spectroscopy, we investigated the excited state of 5-fluoro-4-thiouracil in detail and revealed that it generates more reactive oxygen species (singlet oxygen) than previously studied thionucleobases (Figure 3). This research not only reveals that 5-fluoro-4-thiouracil possesses anticancer properties, but also shows its potential as an excellent drug for photodynamic therapy.

Ms. Sato's interest in research, her inquisitive spirit, and her tireless efforts have borne fruit in this achievement, which has been highly praised and published in the "Topic of Nucleic Acid Photophysics" special issue of the American Society for Photobiology's academic journal, "Photochemistry and Photobiology."

This research is the result of a collaborative effort between Professor Kazuhito Tanabe (Aoyama Gakuin University of Department of Chemistry and Biological Science of College of Science and Engineering and Engineering), Assistant Professor Tatsuya Nishihara (College of Science and Engineering Department of Chemistry and Biological Science Science and Engineering), and Associate Professor Yao-Zhong Xu (School of Life, Health and Chemical Sciences, The Open University, UK) of this university.