VIBRATIONAL CIRCULAR DICHROISM OF THE NUCLEIC ACIDS

V. Adrushchenko and P. Bouř

Institute of Organic Chemistry and Biochemistry, AV ČR, Flemingovo nám. 6, 16610, Praha

Figure: Calculated VCD (De) and absorption (e) spectra of single-stranded octamer (rA)₈ and corresponding experimental VCD and absorption spectra of poly(rA).

Vibrational circular dichroism (VCD) is a difference in absorption of the left- and right circularly polarized light. It is more sensitive to molecular shape than the infrared absorption spectra. For RNA and DNA structures, signs and intensities of VCD peaks depend on sequences, complexation, conformation and hydration of the molecules. Thus the technique is potentially complementary to NMR studies of solution structures, for which X-ray analysis is not possible. However, interpretation of the VCD signal requires complex computations and its accuracy is quite limited for larger molecules. We have developed a method allowing to model vibrational spectra of biopolymers [1], which was based on ab initio computations on smaller fragments, and applied previously for VCD of peptides [2]. The method enabled us to interpret spectra of B- and Z forms of DNA [3] and several RNA structures.

[1] P. BouÍ, J. Sopková, L. Bednárová, P. MaloÁ, T. A. Keiderling, J. Comput. Chem. 18 (1997) 646-659.

[2] P. Bouř, J. Kubelka, T. A. Keiderling, T. A. Biopolymers 65 (2002) 45-69.

[3] V. Andrushchenko, H. Wieser, P. Bouř J. Phys. Chem. B 106 (2002), 12623-12634.