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Xie Jiabao wrote: > Dear all, > > I am using the density modification tool in ccp4 to generate improved phases for/from my model. I find that the electron density map I generate using Fobs, and density modified phases (PHIDM) are not the same as that generated using Fobs, phicalc (original calculated phases) and FOMDM (new improved figure of merit post dm). Can someone please explain to me why this is so? > > Thanks in advance, > Xie > > > > > The calculated map is a fourier transform of h k l W*F, PHI So if youwant a DM style map you need to input F=Fobs W=WDM PHI=PHIDM . Density modifiction will change phases and weights.. ( I think DM may also put out a term FDM which equals WDM*FOBS so you could use F=FDM, PHI=PHIDM)) I dont know what PHICALC is but if you use that phase you must use its associated weight Eleanor