Pharmacologic application of FTIR spectroscopy: effect of ascorbic acid-induced free radicals on Deinococcus...

Fourier transform infrared (FTIR) spectroscopy was used as a convenient and easy-to-run method to monitor radical-induced damage on the radiation-resistant Deinococcus radiodurans strain. Increasing concentrations of ascorbic acid added to the culture medium during the stationary phase produced striking changes in the infrared spectra. These changes especially occurred in the 1700-900 cm(-1) region, which is spectroscopically assigned to the amide I and II components, nucleotide bases, phosphodiester backbone and sugar rings, and were correlated with the oxidant effect of ascorbic acid. Thus, FTIR analysis allows a rapid characterization of the changes induced by ascorbic acid in the cell environment, which can be correlated in part with the generation of free radicals. Beyond a critical ascorbic acid concentration of 40 mM, these free radicals can cause severe damage to the biomolecular components, as soon as the antioxidant defenses of the bacterium are overwhelmed.