Effect of Mg2+binding 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. Blue curve (a) correspond to Raman spectrum in the absence of Mg2+; red curve (b) correspond to Raman spectrum in the presence of 20 mM Mg2+. Spectra were not normalized in order to see the effect of Mg2+ on the phosphodioxy band at 1100 cm-1, but 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+ binding at 20°C.