Helical Symmetry
Standard orientation: z-axis on helical axis, dyad axis on x (if present)
Standard origin: on helical axis, at intersection with dyad axis (if present)
| Description: H<rise>,
<angle>,
<1/2>, <n>* |
Standard Orientation (standard display orientation) | Standard Orientation (perpendicular to z-axis, dyad axis [x-axis] is shown if present) | Standard Orientation (arbitrary display orientation) | Standard Orientation (arbitrary display orientation) |
| Simple Helix: H 10 angs., 120 deg., 1, 1 |
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| A Simple Helix with a Dyad Axis: H 10 angs., 120 deg., 2, 1 |
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| A Simple Helix with a 3-fold
Rotation Axis : H 10 angs., 120 deg., 1, 3 |
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*Helical symmetry is designated by
four symmetry operators:
- A translation (rise per subunit)
- A rotation (rotation angle per subunit), a positive angle signifies a right-handed helix and a negative angle signifies a left-handed helix
- Presence (2) or absence (1) of a dyad axis perpendicular to the helix axis
- n-fold symmetry about the helix axis
- A translation (rise per subunit)
- A rotation (rotation angle per subunit), a positive angle signifies a right-handed helix and a negative angle signifies a left-handed helix
- Presence (2) or absence (1) of a dyad axis perpendicular to the helix axis
- n-fold symmetry about the helix axis
Back to standard origins/orientations table
9 Mar 2006