A-DNA sugar-phosphate
backbone<>
B-DNA sugar-phosphate
backbone<>
Z-DNA sugar-phosphate
backbone<>
A-DNA bases<>
B-DNA bases<>
Z-DNA bases<>
II.
Major and Minor Grooves
Rotating the molecule 90o reveals the grooves in A-DNA <>. The bases are shown in spacefill, the
backbone in wireframe.
Rotating the molecule 90o reveals the grooves in B-DNA<>. The bases are shown in spacefill, the
backbone in wireframe.
Rotating the molecule 90o reveals the grooves in Z-DNA<>. The bases are shown in spacefill, the
backbone in wireframe.
III.
Base Pairs
A single G-C base-pair in A-DNA
A single G-C base-pair in B-DNA
A single G-C base-pair in Z-DNA
Can you identify the major and minor grooves for each?
IV.
Torsion Angles
Torsion angles in A-DNA guanine
delta<>
chi<>
Torsion angles in B-DNA guanine
delta<>
chi<>
Torsion angles in Z-DNA guanine
delta<>
chi<>
| Property | A-Form | B-Form | Z-Form |
|---|---|---|---|
| Helical sense | Right-handed | Right-handed | Left-handed |
| Repeating helix unit | 1 base pair | 1 base pair | 2 base pairs |
| Rotation/base pair (degrees) | 33.6 | 35.9 +/- 4.2 | -60/2 |
| Mean base pairs/turn | 10.7 | 10.0 +/- 1.2 | 12 |
| Inclination of base normals to helix axis (degrees) | +19 | -1.2 +/- 4.1 | -9 |
| Rise/base pair along helix axis (Å) | 2.3 | 3.32 +/- 0.19 | 3.8 |
| Pitch/turn of helix (Å) | 24.6 | 33.2 | 45.6 |
| Mean propeller twist (degrees) | +18 | +16 +/- 7 | ~0 |
| Glycosyl angle conformation | anti | anti | anti at C, syn at G |
| Sugar pucker conformation | C3'-endo | O1'-endo to C2'-endo | C2'-endo at C, C2'-exo to C1'-exo at G |
References: