Volume 2 Chapter 1 Build menu REPEAT

Function

REPEAT is used as a short-cut in generating multiple occurrences of an "internal" repeat unit.

Example

Suppose we wish to search for structures containing (i) - see below.

We might proceed as follows:

Build fragment (ii).

Select REPEAT

Please use the cursor to select the left -most point in your
ligand or repeat.

Select point a at mid-point of C - C bond

Please use the cursor to select the right-most point in your
ligand or repeat.

Select point b at mid-point of the other C - C bond

Please use the cursor to select the upper point in your ligand or
repeat.

Select point c

Please use the cursor to select the lower point in your ligand or
repeat.

Select point d
A white + appears at the four points as you select them.
```
Please type the multiplier
```
Type 3 <R>
The fragment is now as in (iii).

The above example illustrates the use of REPEAT for a simple case, where the repeat unit is just one atom. It can be used for more complex repeat units e.g. (iv).

The correct order of point selection is as shown in (v). If you get the points in the wrong order, the program sounds an alert and produces the error message:

ERROR-Points in wrong order. Operation cancelled.

The maximum number of different repeat units allowed in one structure is 9.

Note also that you are NOT allowed to define a repeat unit within a ligand, or vice-versa.

To edit and delete repeat units see EDIT-REP and DEL-REP in the EDIT menu (chapter 5).

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Volume 2 Chapter 1 Build menu RING .