Table 1. Global helical parameters of duplexes with five-membered sugars.

DNA type	Average helical twist (°)	Average helical rise per residue (Å)	No. of nucleotides per helix	Base pair inclination (°)	x-displacement (Å)
Right-handed helix
Da	45.0	3.02	8.0	–15.9	1.05
Cb	39.5	3.31	8.5	–17.0	3.45
α-DNA:β-DNAc	39.8	3.37	10.1	–3.1	–1.16
Bd	36.1	3.37	10.0	2.4	0.80
RNA:DNA duplexe	32.7	2.62	11.0	11.7	–4.46
Ad	31.1	2.90	11.5	12.0	4.10
Left-handed helix
Zd	–30.0	3.8	12.0	–6.2	3.3

^aValues from Curves (10) on the D-DNA model from Eschenmoser and Dobler (4).

^bCurves calculation on C-DNA model (BII_9_1_model.pdb from http://www.fos.su.se/physical/lorens/) (9).

^cα-/β-DNA: Curves calculation on the reconstructed model (11).

^dValues from Eschenmoser and Dobler (4).

^eCurves calculation on the structure of the RNA:DNA duplex, pdb entry 124D (6).