Limitations

The ARP/wARP procedure requires the use of reciprocal space refinement, density map calculation and the ARP/wARP software itself. The least-squares minimisation can be done with the CCP4 CCP4 programs PROTIN / REFMAC refmac with an optional additional scaling (e.g. using RSTATS). Use of other programs for least-squares minimisation, e.g. SHELXL shelx97, 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 EXTEND/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 may not be 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.

Maximum map section size is 400,000 points. The maximum number of map sections is 1,000. The maximum number of atoms in extended real space asymmetric unit is 250,000

4.

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

5.

ARP/wARP operates with coordinate files in the standard PDB format