Dear Alisia I assume you have read the documentation at
https://www.ccp4.ac.uk/html/scaleit.html in particular the comment "Note that there is no unique solution to the problem of scaling together two different data sets. “ The program was written (a long time ago) to scale a heavy-atom derivative dataset roughly to a native set, with the expectation that the scale (and relative B-factor (isotropic or anisotropic)) would be refined during the derivative refinement procedure, where the underlying difference between datasets can be modelled explicitly The functions used are described in the documentation The underlying assumption of any data scaling is that the true intensities which are compared, from different crystals or from different parts of data collected from the same crystal, are truly the same, and the observations differ only by a scale which can be modelled simply, and by random errors. This clearly is not the case if the crystals are different, for whatever reason, eg by the addition of a heavy atom or a ligand or indeed by radiation damage. So different scaling targets are likely to give (slightly) different results, because of different weighting of observations. In Scaleit, the observed difference is modelled by a relative scale and a relative B-factor (ie a scale dependent on resolution). Note also that ideally the scaling should be done on intensities, rather than on F^2 where the F has been derived from I by the French & Wilson “truncate” procedure or its equivalent. However in practice I’m not sure it makes much difference, given the other assumptions Does this help? Phil > On 12 May 2022, at 22:43, Fadini, Alisia <alisia.fadin...@imperial.ac.uk> > wrote: > > Dear all, > > I am having trouble following from the documentation what specific functions > are minimized in SCALEIT for the different REFINE options and how the > Fox&Holmes method is applied. Any insight would be very helpful! > > All the best, > Alisia > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
