Researchers Develop Nanoscale Probes for ssDNA Sustainability under UV radiation

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DNA, which stores genetic information in the majority of organisms on Earth, is not easily destroyed. It readily absorbs ultraviolet (UV) radiation, but finds ways to recover.

To combat radiation's damage, cells have developed DNA repair mechanisms, as well as mechanisms to remove the energy before it breaks the DNA, such as autoionization, which is the process by which the macro-molecule in an excited state spontaneously emits one of its electrons, releasing a huge amount of energy. Understanding this mechanism is critical to investigating and mitigating the effects of radiation on living organisms.

A team of researchers from Lehigh University (Slava V. Rotkin, Tetyana Ignatova, Michael Blades), the University of Central Florida (Alexander Balaeff), the National Institute of Standards and Technology (Ming Zheng) and a student from the University of Rochester participating in the NSF-Supported "Research Experiences for Undergraduates" (REU) Summer Program at Lehigh (Peter Stoeckl) set out to understand the stability of DNA as a carrier of genetic information against potential damage by UV radiation. They have reported their findings in a paper recently accepted for publication in Nano Research.

Rotkin and his colleagues studied self-assembled complexes of DNA wrapped around single-wall carbon nanotubes utilizing a special technique: two-color photoluminescence spectroscopy. Using the UV and green light simultaneously to probe the sample provided a perspective that no one had been able to observe before in single-color experiments. Later, a quantum mechanical theory was developed to support the experimental data and they were able to confirm a very fast DNA autoionization rate.

"Being able to establish the efficiency of the autoionization process is a key step in understanding how UV-excited DNA can 'cool down' without breaking, thus keeping its normal biological functions," said Rotkin, a professor in Lehigh's Department of Physics and Department of Materials Science & Engineering.

The team's innovative approach has great potential for monitoring DNA excitation, autoionization and chemical damage important for such diverse fields as medicine, evolutionary biology, and space exploration. For biomedical purposes, the ability to study the autoionization mechanism could contribute to an understanding of the survivable levels of UV radiation for different cell types and ways to mitigate irradiation effects. From an evolutionary perspective, it is important to understand the dissipation mechanisms which were crucial during primordial cell evolution when UV radiation was orders of magnitude more intense than today while the DNA repair mechanisms were presumably non-existent. For continued exploration of space, it is important to develop strategies for cellular and organismal safety in harsh radiation conditions.

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