Re: [ccp4bb] What makes the difference between 2 composite omit maps?
I am not aware of this point being explicitly made. Maybe somebody else could point to the relevant reference? However, the logic here is very simple: (1) Take a model and generate from it Fc (2) Calculate map with minimal rms error m*Fo*exp(i*phiCalc) (3) This map is biased with respect to errors in the model (4) To avoid this bias one can subtract a part of the model (Fc*coefficient) from the above map - the coefficient is chosen so electron density in the resulting map does not change at the point where we added or subtracted an atom; - conceptually the above procedure when we subtract an atom is the composite omit map - "does not change" means here: within first order approximation, we ignore second order effects - for sigmaA-weighted map this coefficient is D/2 (5) The subtraction gives: (m*Fo-D/2*Fc)exp(i*phiCalc) (6) After multiplication by 2, we get (2m*Fo-DFc)exp(i*phiCalc) Hailiang Zhang wrote: Thanks! Can you refer me some documents about your following statements: derivation of sigmaa-weighted 2mFo-DFc formula is by calculating Fourier coefficients of the following map: Rescaled composite omit map, where minimal structural element (of the size about the resolution element) is being omitted and the starting point is the map with coefficients m*Fo*exp(i*phiCalc) It seems the above was not involved in Read's publications about SIGMAA. Thanks again! Hailiang sigmaa-weighted 2mFo-DFc is the _COMPOSIT_OMIT_ map. There is no point in calculating omit map of an omit map A brief explanation: derivation of sigmaa-weighted 2mFo-DFc formula is by calculating Fourier coefficients of the following map: Rescaled composite omit map, where minimal structural element (of the size about the resolution element) is being omitted and the starting point is the map with coefficients m*Fo*exp(i*phiCalc) BTW, composite omit map of a map with coefficients Fo*exp(i*phiCalc) is simply Fo-1/2Fc map that after factor of 2 scaling becomes 2Fo-Fc map Hi, I want to calculate the sigmaa-weighted 2mFo-DFc composite omit map, and tried the following 2 scripts: (1) ./omit hklin ${f}.mtz mapout ${f}.map < concerned about which one is more appropriate for the sigmaa-weighted 2mFo-DFc composite omit map. (mFo is what I generated from the SIGMAA output) Thanks for any suggestions! Best Regards, Hailiang Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353 Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353 -- Zbyszek Otwinowski UT Southwestern Medical Center 5323 Harry Hines Blvd., Dallas, TX 75390-8816 (214) 645 6385 (phone) (214) 645 6353 (fax) zbys...@work.swmed.edu
Re: [ccp4bb] What makes the difference between 2 composite omit maps?
Thanks! Can you refer me some documents about your following statements: derivation of sigmaa-weighted 2mFo-DFc formula is by calculating Fourier coefficients of the following map: Rescaled composite omit map, where minimal structural element (of the size about the resolution element) is being omitted and the starting point is the map with coefficients m*Fo*exp(i*phiCalc) It seems the above was not involved in Read's publications about SIGMAA. Thanks again! Hailiang > sigmaa-weighted 2mFo-DFc is the _COMPOSIT_OMIT_ map. There is no point in > calculating omit map of an omit map > > A brief explanation: derivation of sigmaa-weighted 2mFo-DFc formula is by > calculating Fourier coefficients of the following map: > > Rescaled composite omit map, where minimal structural element (of the size > about the resolution element) is being omitted and the starting point is > the map with coefficients m*Fo*exp(i*phiCalc) > > BTW, composite omit map of a map with coefficients Fo*exp(i*phiCalc) is > simply Fo-1/2Fc map that after factor of 2 scaling becomes 2Fo-Fc map > >> Hi, >> I want to calculate the sigmaa-weighted 2mFo-DFc composite omit map, and > tried the following 2 scripts: >> >> (1) >> ./omit hklin ${f}.mtz mapout ${f}.map <> LABI FP=mFo FC=DFC PHI=PHIC >> RESO 29.50 3.22 >> SCAL 2.0 -1.0 >> EOF >> >> (2) >> ./omit hklin ${f}.mtz mapout ${f}.map <> LABI FP=FWT FC=FC PHI=PHIC >> RESO 29.50 3.22 >> SCAL 1.0 0.0 >> EOF >> >> The output maps are just different, and I wonder why. I am also more > concerned about which one is more appropriate for the sigmaa-weighted > 2mFo-DFc composite omit map. >> >> (mFo is what I generated from the SIGMAA output) >> >> Thanks for any suggestions! >> >> Best Regards, Hailiang >> > > > Zbyszek Otwinowski > UT Southwestern Medical Center at Dallas > 5323 Harry Hines Blvd. > Dallas, TX 75390-8816 > Tel. 214-645-6385 > Fax. 214-645-6353 > > > > Zbyszek Otwinowski > UT Southwestern Medical Center at Dallas > 5323 Harry Hines Blvd. > Dallas, TX 75390-8816 > Tel. 214-645-6385 > Fax. 214-645-6353 > >
Re: [ccp4bb] What makes the difference between 2 composite omit maps?
sigmaa-weighted 2mFo-DFc is the _COMPOSIT_OMIT_ map. There is no point in calculating omit map of an omit map A brief explanation: derivation of sigmaa-weighted 2mFo-DFc formula is by calculating Fourier coefficients of the following map: Rescaled composite omit map, where minimal structural element (of the size about the resolution element) is being omitted and the starting point is the map with coefficients m*Fo*exp(i*phiCalc) BTW, composite omit map of a map with coefficients Fo*exp(i*phiCalc) is simply Fo-1/2Fc map that after factor of 2 scaling becomes 2Fo-Fc map > Hi, > I want to calculate the sigmaa-weighted 2mFo-DFc composite omit map, and tried the following 2 scripts: > > (1) > ./omit hklin ${f}.mtz mapout ${f}.map < LABI FP=mFo FC=DFC PHI=PHIC > RESO 29.50 3.22 > SCAL 2.0 -1.0 > EOF > > (2) > ./omit hklin ${f}.mtz mapout ${f}.map < LABI FP=FWT FC=FC PHI=PHIC > RESO 29.50 3.22 > SCAL 1.0 0.0 > EOF > > The output maps are just different, and I wonder why. I am also more concerned about which one is more appropriate for the sigmaa-weighted 2mFo-DFc composite omit map. > > (mFo is what I generated from the SIGMAA output) > > Thanks for any suggestions! > > Best Regards, Hailiang > Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353 Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353
[ccp4bb] What makes the difference between 2 composite omit maps?
Hi, I want to calculate the sigmaa-weighted 2mFo-DFc composite omit map, and tried the following 2 scripts: (1) ./omit hklin ${f}.mtz mapout ${f}.map <