A diffraction data set has been collected from a blood coagulation factor X
III-Ca2+ complex crystal at the X-ray diffraction beamline of the ELETTRA s
ynchrotron (Trieste, Italy) at a wavelength of 2.6 Angstrom. The data colle
ction could be carried out using the beamline as is, without making any tim
e-consuming changes to the apparatus. Various data-processing schemes have
been employed and it has been observed that local or detector scaling proce
dures are essential for producing the 'best' anomalous differences.