Comparison of base inclination in ribo‐AU and deoxyribo‐AT polymers

The inclination angle between the base normal and the helix axis is measured for ribo-AU polymers by using flow linear dichroism (LD), and compared to measurements for deoxyribo-AT polymers under dehydrating conditions. The CD of the DNA polymers under the dehydrating conditions is not the same as the corresponding RNA polymers, which are presumed to be in the A form. However, the LD indicates that poly(dAdT)-poly(dAdT) can assume the A form in 80% 2,2,2-trifluoroethanol, although poly(dA)-poly(dT) retains B form structure in this dehydrating solvent. The inclination angles are similar for B form poly(dAdT)-poly(dAdT) and poly(dA)-poly(dT), and these parameters are also similar for A form poly(rArU) -poly(rArU) and poly(rA) -poly(rU). All the inclination axes are similar. © 1995 John Wiley & Sons, Inc.