Synthetic DNA bases created in 2014 to expand the genetic code are light-sensitive and produce reactive oxygen species (ROS) when exposed to certain wavelengths.

Ultraviolet light can damage natural DNA bases, but cells have in-built repair mechanisms to fix this. Carlos Crespo-Hernández of Case Western Reserve University in Cleveland, Ohio, and his co-workers found that two lab-made DNA bases — d5SICS and dNaM, which have been used to design semi-synthetic bacteria — generate up to 100 times more reactive species than the most reactive natural base, thymidine, when exposed to near-visible wavelengths of light. In response to light exposure, a carcinoma cell line grown with d5SICS had higher levels of ROS, and cell proliferation was reduced.

Synthetic DNA bases may accelerate photochemical damage to cells, the authors say.

J. Am. Chem. Soc. http://doi.org/bp55 (2016)