Xscale

XSCALE ist the scaling program of the XDS suite. At the XDS website, there is a short a long commented example of XSCALE.INP

A minimal input file to combine two datasets into one file is:

OUTPUT_FILE=fae-merge.ahkl 
INPUT_FILE= ../fae-ip/xds_1/XDS_ASCII.HKL
INPUT_FILE= ../fae-ip/xds_2/XDS_ASCII.HKL

Radiation damage correction

To "switch on" radiation damage correction (K. Diederichs, S. McSweeney and R. B. G. Ravelli (2003) Zero-dose extrapolation as part of macromolecular synchrotron data reduction. Acta Cryst. D59, 903-909) it suffices to use the CRYSTAL_NAME keyword. The CRYSTAL_NAME parameters of different datasets do not have to be different. If they are different, this results in more degrees of freedom (namely, the slopes of the reflection intensity as a function of dose) for the program to fit the observed changes of intensities which are induced by radiation damage. However, if the datasets are based on the same crystal, or the datasets are based on crystals from the same drop, it is reasonable to assume that the slopes are the same. Example:

OUTPUT_FILE=fae-merge.ahkl 
  INPUT_FILE= ../fae-ip/xds_1/XDS_ASCII.HKL  !
  CRYSTAL_NAME=ip
  INPUT_FILE= ../fae-ip/xds_2/XDS_ASCII.HKL  ! same crystal, but translated along z
  CRYSTAL_NAME=ip

This is the recommended way as it avoids overfitting.

If, however, the crystals represent different heavy atom soaks, it is advisable to give a different CRYSTAL_NAME to each dataset. Example:

OUTPUT_FILE=hg.ahkl 
  INPUT_FILE= ../xds-hg/XDS_ASCII.HKL  ! a mercury soak
  CRYSTAL_NAME=Hg

OUTPUT_FILE=pt.ahkl
  INPUT_FILE= ../xds-pt/XDS_ASCII.HKL  ! a platinum soak
  CRYSTAL_NAME=Pt

A hint for long-time XSCALE users

The latest versions do not require

SPACE_GROUP_NUMBER=
UNIT_CELL_PARAMETERS=

in XSCALE.INP because these parameters are picked up from the header of the first input reflection file.