Limitations

The ARP/wARP procedure requires the use of reciprocal space refinement, density map calculation and the ARP/wARP software itself. The minimisation can be done with the CCP4 [7] programs PROTIN / REFMAC [12]. Use of other programs for minimisation, e.g. SHELXL [8], requires additional conversion to the CCP4 format which is provided within the ARP/wARP package. Density map calculations are carried out with the CCP4 programs FFT and MAPMASK.
As ARP/wARP runs in conjunction with programs of the CCP4 suite all limitations of the latter remain. Note that the CCP4 ARP version, arpp, is not equivalent and is not compatible with the full ARP/wARP package. ARP/wARP itself is limited to:

1.

The CCP4 conventions should be set up before running ARP/wARP 

2.

Density maps and reflection MTZ files in the CCP4 format

3.

ARP/wARP operates with coordinate files in standard PDB format

4.

Only acentric space groups (typical for proteins) and P1 are supported