Circular dichroism and UV-Vis detection of UV-induced damage to nucleic acids

In this report, we demonstrate that CD spectroscopy can be used as a tool to detect changes to DNA upon irradiation with UV light. We follow the spectroscopic response of DNA samples irradiated at selected exposure times with both CD and UV-Vis spectroscopy. We analyzed four different nucleic acids to evaluate the effect of the sequence on photodegradation. Only one polymer, calf thymus DNA, was a natural nucleic acid and contained all four nucleobases. The other three were synthetic polymers and contained only one type of base pair: poly (deoxyadenylic-deoxythymidylic) acid [poly (dA-dT)(2)] and poly (deoxyadenylic acid) & BULL; poly (deoxythymidylic acid) [poly (dA) & BULL; poly (dT)], which contained only adenine and thymine; poly (deoxyguanylic-deoxycytidylic) acid [poly (dG-dC)(2)], which contained only guanine and cytosine. CD and UV-Vis spectra showed sequence dependent changes. In particular, poly (dA) & BULL; poly (dT) undergoes changes more rapidly than the other sequences investigated. The CD spectrum of poly (dA) & BULL; poly (dT) gradually undergoes an inversion, suggesting a change in helicity, before disappearing due to the unfolding of the double strand.

Automated summary

In this report, we show that CD spectroscopy is a useful tool for detecting changes in DNA caused by UV light irradiation. By using both CD and UV-Vis spectroscopy, we monitor the spectroscopic response of DNA samples exposed to UV light for different durations. We studied four different nucleic acids to understand the impact of sequence on photodegradation, and observed sequence-dependent changes in CD and UV-Vis spectra, with poly (dA)•poly (dT) showing the most rapid changes.