Comparison of base inclination in ribo-GC and deoxybribo-GC polymers,and synthesis of poly(rGrC)-poly(rGrC)

The inclination angle between the base normal and the helix axis, and the axes around which the bases incline, are measured for ribo-GC polymers in buffer by using flow linear dichroism (LD), and compared to measurements for deoxyribo-GC polymers in buffer and under dehydrating conditions. A new method is designed to synthesize poly(rGrC) -poly(rGrC), which is not available commercially, in large quantities. The LD of this RNA reveals inclination angles that are similar to the B-form DNA in buffer, although the axes are different. The CD of poly(dGdC)-poly(dGdC) under the dehydrating conditions is similar to poly(rGrC)-poly(rGrC), indicating it is in the A form, and the LD gives larger inclination angles than either the B form or the corresponding RNA. Poly(dG)-poly(dC) is in the A form in buffer. Comparison among poly(rG)-poly(rC) in buffer, and poly (dG)-poly(dC) in buffer and under dehydrating conditions, reveals similar inclination angles and axes, although the LD shows that the DNA has the largest inclination angles. Except for poly(rGrC)-poly(rGrC), which has a unique reduced dichroism, all the axes for G are similar, as are the axes for C. © 1995 John Wiley & Sons, Inc.