X-ray radiation-induced damage in DNA monitored by online Raman

High-quality Raman spectra have been collected on single DNA crystals kept at 100 K in a flow of cold nitrogen gas prior, during and after macromolecular crystallography (MX) data collection. The non-symmetric bending vibration for C-Br bonds in 8-bromo-2'-deoxyguanosine has been unambiguously identified at 293 cm-1 in the non-resonant Raman spectra. The breakage of this bond could be monitored by the continuous recording of Raman spectra during X-ray exposure, and its decay versus dose could be directly correlated with the loss of the bromide definition within the electron-density maps as determined with MX