Comparison of base inclinations for left‐handed DNA and RNA

Abstract

SYNOPSISThe Z-form of poly(dG-m5dC)~poly(dG-m5dC) in 85% ethanol/MOPS and the Z-form poly ( rG-rC ) . poly ( rG-rC) in 4.8 M NaClO,, 20% ethanol are studied by flow linear dichroism. Simultaneous analysis of the isotropic absorption and linear dichroism data yields the angle of inclination of the base normal relative to the helix axis, and the orientation of the axis around which the bases incline. For the Z-form of poly(dGm5dC) .poly(dG-m5dC) the inclination angles are 31.3" for guanine, and 27.9" for cytosine; for the Z-form of poly(rG-rC).poly(rG-rC) they are 25.0" for guanine, and 23.3" for cytosine. The inclination angles for the Z-form DNA are similar to those for the Zform, and the angles for Z-form RNA are somewhat smaller. The axes of inclination for guanine and cytosine are similar in all three left-handed forms. 0 1995 John Wiley & Sons, Inc.