In a next-generation solar cell, light also transfers electrons, but in DNA, the researchers observe that the transferred electron returns to its starting point in a fraction of a nanosecond. The back-and-forth motion of the electron explains how DNA remains undamaged most of the time. At the same time, the researchers note that the transferred electron could be used to repair damage in a way that mimics how certain repair proteins fix UV damage.
The finding is the latest in Kohler's 15-year search to understand what happens to DNA when it absorbs UV light.
The new discovery was possible because of a "lovely" infrared laser instrument built by Yuyuan (Tom) Zhang, an expert in ultrafast spectroscopy, a postdoctoral researcher at MSU and first author of the PNAS paper, Kohler said.
Zhang came to MSU about two years ago, and his first job was building the instrument that's the only one of its kind in Montana and one of only a handful in the world. The instrument shoots extremely short pulses of ultraviolet light at DNA samples, then measures the vibrations created in DNA in response. The vibrations are so fast that Kohler describes their speed in terms of femtoseconds instead of nanoseconds. A femtosecond is one millionth of a nanosecond. A nanosecond is one billionth of a second.
By analyzing those vibrations, the research team was able to determine that one base in a single strand of DNA transfers an electron to an adjacent base on the same strand when excited by UV light (or radiation), Kohler said. He added that molecules constantly vibrate, and light absorption leads to even greater vibrations. Removing or adding an electron causes changes to the pattern of vibrations, and that is what the MSU team measured in the lab.
|Contact: Evelyn Boswell|
Montana State University