Volume 2 Chapter 5 Edit Menu RESIDUE

Function

RESIDUE allows the editing operations to be applied to a single residue of the structure.

Remarks

The valid editing operations which can be applied to a residue are:

CENTRE
SCALE
DELETE
SHIFT
ROTATE
SYMMETRY
TWIN

Examples

Suppose (i) is the starting fragment.

(i)

Select RESIDUE
```
Select any ATOM in the required RESIDUE
```
Select O atom.

The 3-membered ring is now the active residue.

Select SHIFT

Select any active atom
(or select another command to CANCEL SHIFT)

Select O atom

Now select new position for this atom (or
select another command to CANCEL SHIFT)

Select position a
Fragment is now (ii).
(ii)

Note that SHIFT is the default option for RESIDUE, so when you select an atom in an active residue you are prompted to locate its new position.

Select ROTATE

Enter ANGLE (in degrees) for ROTATE
(A POSITIVE number will give an ANTICLOCKWISE rotaation.)

Type 180 <R>

The program now prompts for the centre of rotation after you specify the angle of rotation. This may be either an atom, a grid point or a point in "free space".

```
Please select the ORIGIN of rotation
```
Select a point in the centre of the CCO triangle residue
Fragment is now (iii), i.e. it has been rotated by 180 degrees around its geometric centre.
(iii)
Select CENTRE
The 3-membered ring is moved so that its centroid is at the centre of the drawing area.
Fragment is now (iv).
(iv)
Select SCALE
The EDIT menu options vanish and a scale bar is drawn at the right-hand side of the drawing area - see (v). The range of scaling is from double to half.

(v)

Select a point on the SCALE BAR, to rescale your structure.
(Select any other area to end SCALE)

Select point b
The diagram is re-drawn with 3-membered ring scaled up by ca. 1.5 - see (vi).
(vi)
The origin of scaling is the geometric centre of the active residue.

Select a point on the SCALE BAR, to rescale your structure.
(Select any other area to end SCALE)

Select point d
The scale bar vanishes and the EDIT menu commands are restored.
Select TWIN
The diagram is re-drawn (and may be rescaled) and now contains a twin (copy) of the active residue - see (vii). The active residue is the 3-membered ring labelled e.
Select DELETE
The active residue is deleted.
The fragment is now (viii).
No part of the fragment is now active so the program prompts you:

Please select a unit to be edited (such as WHOLE or ATOM)

A description of the use of SYMMETRY is detailed under WHOLE.

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Volume 2 Chapter 5 Edit Menu UNDO .