Conformation of double-stranded polydeoxynucleotides in solution by proton two-dimensional nuclear Overhauser enhancement spectroscopy.

Proton 2D-NOE spectroscopy has been used to investigate the three-dimensional conformations of several sonicated polydeoxynucleotides in solution. The observed pattern of cross peaks indicate that poly(dAdT) . poly(dAdT1 in all salt concentrations studied (up to 6.6M CsF), and poly(dG-m5dC) . poly(dG-m5dC) in low salt (0.1M NaCU are righthanded B-structures. Poly(dG-m5dC) . poly(dG-m5dC) in Mg2+ (3 mM) solution exhibits a pattern characteristic of the left-handed Z-form. These results for poly(dA-dT) poly(dA-dT) are in contrast to suggestions that this copolymer exists as a left-handed form, either in low or high salt. We present pure absorption-mode ZD-NOE spectra that enable us to compare several distances and define the conformations of these polydeoxynucleotides in solution.