When anomalous data are collected at a variety of wavelengths such as in a MAD experiment the relative scale of the data can be affected in different ways such as different absorption effects or changes in the beam intensity. These fluctuations could ultimately lead to the success or failure of the data to solve the structure as the accuracy required of MAD data is extremely high. If the data could be re-scaled in some way to smooth out or remove these fluctuations it may be easier to determine the positions of the anomalous scatterers. This is what the program REVISE aims to do.
REVISE is used to modify MAD data in order to estimate FM, the normalised anomalous scattering magnitude as defined in Equation (2). The difference between FM and the normalised structure factor E is that FM contains a scale factor and a temperature factor. FM can be used to calculate anomalous Patterson maps or for input to Direct Methods to locate the positions of anomalous scatterers.
The program is based on two features which only exist in MAD data. For each reflection, one can write these equations:
[(FPHn(-))**2 - (FPHn(+))**2]/f"n = constant (1) [(FH'n)**2 + (FH"n)**2]/[(f'n)**2 + (f"n)**2] = (FM)**2 (2) where: FPHn(+) - total structure factor for h,k,l. FPHn(-) - total structure factor for -h,-k,-l. FH'n - real part of anomalous scattering structure factor. FH"n - imaginary part of anomalous scattering structure factor. n - wavelength n. f'n - real component of anomalous scatterer. f"n - imaginary component of anomalous scatterer.and both should be independent of wavelength.
The FPHn(+) and FPHn(-) can be modified to satisfy Equation (1) minimizing any fluctuations. Equation (2) is used to estimate the total anomalous scattering for each reflection [reference 1]. The program uses trial and error to find a suitable range and aims to minimize differences in FM between all the wavelengths. A figure of merit indicates the minimum point and then the program takes the average value of FM for each wavelength as a final value of FM. In general the use of FM rather than anomalous differences can lead to better results in the determination of the positions of the anomalous scatterers.
The program can handle up to ten wavelength anomalous scattering data sets. A minimum of at least two sets are required. REVISE does not require native protein data, FP, and can only copy FP from input file to output file.
END, EXCL, LABIN, LABOUT, RESO, TITLE, WAVE
<rmax> the high resolution limit in Angstrom. If this command is absent, the default is to use all reflections in the file.
FP SIGFP DP SIGDP FPH1(+) SIGFPH1(+) FPH1(-) SIGFPH1(-) FPH1 SIGFPH1 DPH1 SIGDPH1 FPH2(+) SIGFPH2(+) FPH2(-) SIGFPH2(-) FPH2 SIGFPH2 DPH2 SIGDPH2 ........... FPH10(+) SIGFPH10(+) FPH10(-) SIGFPH10(-) FPH10 SIGFPH10 DPH10 SIGDPH10Example:
LABI - FPH1(+)=FP1 SIGFPH1(+)=SFP1 FPH1(-)=FN1 SIGFPH1(-)=SFN1 - FPH2(+)=FP2 SIGFPH2(+)=SFP2 FPH2(-)=FN2 SIGFPH2(-)=SFN2 - FPH3(+)=FP3 SIGFPH3(+)=SFP3 FPH3(-)=FN3 SIGFPH3(-)=SFN3
FPHM1(+) SIGFPHM1(+) FPHM1(-) SIGFPHM1(-) FPHM1 SIGFPHM1 DPHM1 SIGDPHM1 FPHM2(+) SIGFPHM2(+) FPHM2(-) SIGFPHM2(-) FPHM2 SIGFPHM2 DPHM2 SIGDPHM2 .................... FPHM10(+) SIGFPHM10(+) FPHM10(-) SIGFPHM10(-) FPHM10 SIGFPHM10 DPHM10 SIGDPHM10 FM SIGFMExample:
LABO - FPHM1(+)=FP1_mod SIGFPHM1(+)=SFP1_mod - FPHM1(-)=FN1_mod SIGFPHM1(-)=SFN1_mod - FPHM2(+)=FP2_mod SIGFPHM2(+)=SFP2_mod - FPHM2(-)=FN2_mod SIGFPHM2(-)=SFN2_mod - FPHM3(+)=FP3_mod SIGFPHM3(+)=SFP3_mod - FPHM3(-)=FN3_mod SIGFPHM3(-)=SFN3_mod - FM=FM_RE SIGFM=SFM_RE
Example: WAVE 1 LAM 0.9000 FPR -1.622 FDP 3.285 WAVE 2 LAM 0.9795 FPR -8.198 FDP 2.058 WAVE 3 LAM 0.9809 FPR -6.203 FDP 3.663
If [|DISO|/FPH] > <riso>
then rejection occurs.
Default: <riso> = 0.10 (10%);
If [|DANO|/FPH] > <rano> then
rejection occurs. Default: <rano> = 0.50 (50%);
If [|FPH|/SIGFPH|] < <sigm> then
rejection occurs. Default: <sigm> = 0.0.
Example: EXCL RISO 0.15 RANO 0.40 SIGM 3.0
Here are the definitions for each label:
Name Item H, K, L Miller indices. FP F value for native protein. SIGFP Sigma(FP). DP Anomalous difference for native data. SIGDP Sigma(DP). FPHn(+) FPH(h,k,l) for wavelength 'n'. SIGFPHn(+) Sigma(FPHn(+)). FPHn(-) FPH(-h,-k,-l) for wavelength 'n'. SIGFPHn(-) Sigma(FPHn(-)). FPHn FPHn = 0.5 * (FPHn(+) + FPHn(-)). SIGFPHn Sigma(FPHn). DPHn DPHn = FPHn(+) - FPHn(-). SIGDPHn Sigma(DPHn). FPHMn(+) Modified FPH(h,k,l) for wavelength 'n'. SIGFPHMn(+) Sigma(FPHMn(+)). FPHMn(-) Modified FPH(-h,-k,-l) for wavelength 'n'. SIGFPHMn(-) Sigma(FPHMn(-)). FPHMn FPHMn = 0.5 * (FPHMn(+) + FPHMn(-)). SIGFPHMn Sigma(FPHMn). DPHMn DPHMn = FPHMn(+) - FPHMn(-). SIGDPHMn Sigma(DPHMn). FM anomalous contributions after applying REVISE. SIGFM Sigma(FM).
Statistics of the ratio
[(FPHn(-))**2 - (FPHn(+))**2] / [(FPHm(-))**2 - (FPHm(+))**2]
between data set n and data set m are then printed in 10 resolution ranges, for both before and after the revise procedure. It follows from equation (1) that this ratio should be equal to the ratio of f"n/f"m, and the revise procedure will tend to ensure this. Distributions of the ratios before the revise procedure are also given as XLOGGRAPH plots, and these can be used as a guide to data quality.
Details of the output file are printed at the end of log file.
revise \ hklin $HOME/test.mtz \ hklout $SCRATCH/test-revise.mtz\ << eof TITLE testing revise LABI - FPH1=FSe1 SIGFPH1=SIGFSe1 DPH1=DSe1 SIGDPH1=SIGDSe1 - FPH2=FSe2 SIGFPH2=SIGFSe2 DPH2=DSe2 SIGDPH2=SIGDSe2 - FPH3=FSe3 SIGFPH3=SIGFSe3 DPH3=DSe3 SIGDPH3=SIGDSe3 LABO - FPHM1=FSe1_mod SIGFPHM1=SIGFSe1_mod DPHM1=DSe1_mod - SIGDPHM1=SIGDSe1_mod FPHM2=FSe2_mod SIGFPHM2=SIGFSe2_mod - DPHM2=DSe2_mod SIGDPHM2=SIGDSe2_mod FPHM3=FSe3_mod - SIGFPHM3=SIGFSe3_mod DPHM3=DSe3_mod SIGDPHM3=SIGDSe3_mod - FM=FM_RE SIGFM=SFM_RE WAVE 1 LAM 0.9000 FPR -1.622 FDP 3.285 WAVE 2 LAM 0.9795 FPR -8.198 FDP 2.058 WAVE 3 LAM 0.9809 FPR -6.203 FDP 3.663 EXCL RISO 0.15 RANO 0.40 SIGM 3.0 END eof