Figure 23.3.3.4

Dickerson, R. E.

doi:10.1107/97809553602060000716

International
Tables for
Crystallography
Volume F
Crystallography of biological macromolecules
Edited by M. G. Rossmann and E. Arnold

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International Tables for Crystallography (2006). Vol. F. ch. 23.3, p. 599 | 1 | 2 |

Figure 23.3.3.4

R. E. Dickerson^a ^*

^a Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095–1570, USA
Correspondence e-mail: red@mbi.ucla.edu

Figure 23.3.3.4

Glycosyl conformation and chain sense. (a) Glycosyl conformations anti/anti, backbone chains antiparallel, with clockwise sense when viewed into the minor groove, as here. This is typical for A- and B-DNA. (b) Glycosyl conformation syn/syn, backbone chains antiparallel, with counterclockwise sense viewed into minor groove. This is not known for any nucleic acid duplex. (c) Glycosyl conformation syn at G and anti at C, with the C4′—C3′ edge of the sugar pointing downward in both strands, which would seem to imply a parallel-stranded helix. However, in Z-DNA, antiparallel strands are achieved by a local reversal of chain direction at each C, as shown here. This produces the zigzag backbone pathway that is characteristic of the Z helix, visible in Fig. 23.3.3.3.