Discrimination between UV radiation-induced and thermally induced spectral changes in AT-paired DNA oligomers using UV resonance Raman spectroscopy

Ultraviolet resonance Raman spectroscopy (UVRRS) was used to monitor UV radiation and thermal energy deposition in 12- and 18-mer AT oligomers. Difference spectroscopy and two-dimensional correlation spectroscopy (2DCOS) were used to characterize the distinct spectral responses manifested by the two processes, and to examine their potential cooperative and/or independent effects on the ensemble spectrum. Experiments utilizing incremental doses of 257-nm radiation revealed that the most affected bands are those involving double bonds when the sample temperature was held constant. Complementary experiments utilizing sample heating indicated that the most affected bands were those involving hydrogen-bond disruption. Finally, it is shown that bands associated with Watson-Crick hydrogen-bond disruption are the most affected in rapidly heat-cycled samples. The results also suggest that both radiation and thermal effects produce independent structural changes in AT oligomers and, furthermore, that these effects are complementary when the experiments involve single-strand DNA fragments. When using UVRRS to study one of these perturbations (e.g. thermal stability of DNA), the concurrent perturbation (e.g. UV exposure) must not be neglected, since UV exposure is inherent in the UVRR process. These findings thus have implications for the use of UVRRS in the study of DNA dynamics. Copyright (C) 2006 John Wiley & Sons, Ltd.