Effect of Mg2+-induced self-cleavage on Raman spectra of ASBVds. The Raman spectra of the minus (panel A) and plus (panel B) strands of ASBVd are obtained in cacodylate buffer, in the presence of 20 mM Mg2+. Blue curve (a) correspond to Raman spectrum taken before cleavage; red curve (b) correspond to Raman spectrum taken after cleavage (see text for details). All spectra were normalized using the Raman band at 1100 cm-1; the contributions from the cacodylate buffer and quartz cell were subtracted. The difference spectrum (c) (c = b-a, black curve) was multiplied by a factor of 3 to visually enhance the resulting spectral changes corresponding to Mg2+ induced self-cleavage.