Keywords that control Xray

The SAD target

The SAD target incorporates the phase information from SAD experiment, gaining it directly from the heavy atom coordinates and F+ and F- differences. The requirements of SAD target are at least one element with number of electrons higher than 8 and known f',f'' formfactors present in the input pdb file and the F+,F-,SIGF+,SIGF- labels. The relevant keywords are:

LABIN F+= < label > SIGF+=< label> F-=< label> SIGF-=< label>

If F+,F-,SIGF+,SIGF- are given then SAD target will be used. The input of FP and SIGFP for SAD target is optional.

ANOMalous FORMfactor [Name] [f'] [f'']

Will modify the form factor of the element given by Name.

ANOMalous WAVElength [Wavelengh]

If Wavelength is given then the form factors (f' and f'' of all atoms) will be calculated using crossec.
If Wavelength is given and for some element explicit formfactors are given (by ANOM FORM keyword) then they will be used for this element and other elements' formfactors will be calculated from the Wavelength.
If Wavelength is not given and mtz file has the wavelength then it will be used.
If Wavelength is not given and mtz does not have wavelength info then f'=0,f''=0 will be used for all elements for which formfactors were not specified by ANOM FORM. If SAD target is used then ANOM FORM has to be given for at least one element in this case otherwise an error message is printed.