| Abstract: | Eighteen kinds of oligodeoxyribonucleic acids have been examined to reveal their structures in aqueous solutions at different ionic strengths by Raman spectroscopy. The structures in solutions were found to be very polymorphic depending on their sequences as well as on the salt concentrations. At a low salt condition a DNA oligomer assumes a unique B form within a B family, for examples Ba, Bh, B', or Bn form. Amongst these DNA oligomers, d(CGCG)2 showed a salt induced Ba-Z transition, while d(GGGGCCCC)2 showed a salt induced Bh-A transition. DNA oligomers with AA/TT sequences were found to prefer B' form even at high salt condition. From comparing the structures of DNA oligomers in solutions with their crystal structures, it is safe to say that the crystal structure of a DNA oligomer is very similar to the structure in the high salt solution. |
