Volume 2 Chapter 5 Edit Menu EDIT-LIG

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EDIT-REP

Function

EDIT-REP allows you to alter the position of the brackets and value of the multiplier around a repeat unit in the structure.

Remarks

If your structure contains no repeat units then EDIT-REP is greyed in the EDIT menu so that you cannot select it.

Example

Suppose we have constructed the fragment (i) below

We wish to edit the repeat unit so that the O in the chain is included in the repeat unit.

EDIT-REP allows you to change the multiplier value associated with a repeat unit and then gives you the opportunity to move the corners of the brackets, to change the atoms that lie in the repeat unit.

In the EDIT menu, whenever you shift, scale or rotate part or all of a structure which contains a ligand or repeat unit, the brackets may not fit perfectly around the correct atoms afterwards. So, after every such operation, the program attempts to move the bracket corners to the correct position.

However, occasionally after an editing operation, one of the atoms in the structure which was not in a ligand or repeat comes too close to the ligand or repeat atoms, and so encroaches into the [] or (). The program will sound an alert and enable you to move the offending atom further from the [] or () by following the series of steps outlined for EDIT-LIG or EDIT- REP above.

For example, if the structure in (i) is rotated through 90deg. using the ROTATE command in the EDIT menu, the program will redraw the structure as shown in (ii), trying to incorporate the correct atoms in the repeat unit. In this case the program will sound and alert and produce the message:

If you are not sure which is the offending atom, go to the 2D-CONSTRAIN sub-menu and switch on NUMBERS. This will number each of the atoms in the diagram and enable you to find the offending atom.

The structure can then be edited using EDIT-REP so that it appears as is shown in (iii).

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Volume 2 Chapter 5 Edit Menu ELEMENT TYPES.