RANTAN (CCP4: Supported Program)
NAMErantan - is a Direct Method module for the determination of heavy atom positions in a macro-molecule structure or to determine a small molecule structure.
rantan hklin foo_in.mtz hklout foo_out.mtz
RANTAN  reads in the E values calculated by ECALC and the known phases with weights if they are available. The programme determines the reflections for fixing origin and enantiomorph by CONVERGENCE procedure from MULTAN . A set of random phases with weights (default 0.25) will be assigned to the rest of the large E values in the starting set. The phases will be refined by the tangent formula  and expanded to the whole set of large E values which are enough to determine the positions of heavy atoms or a small molecule structure.
The traditional figures of merit are used to indicate solutions. Up to 5 sets of refined phases and weights with the best combined figures of merit are output.
Input phases with weights greater than 0.85 can be used as known phases and of these those phases with weights greater than 0.98 will not be refined until the last two cycles. These so-called "known" phases will be combined with randomly generated phases as a starting set . If there are more than 80% of large E values with "known" phases, only one set of refined phases will be output.
All the items in the input file will be echoed in the output file plus the new phases and weights. For MAD data, REVISE should be used first to obtain the estimates of FM, from which E values can be calculated by ECALC and input to RANTAN.
RANTAN can be used to determine a small molecule structure too, but all the default values are for the determination of heavy atom sites in a macro-molecule structure. When ECALC is used to calculate the E values for a small molecule, the number of reflections in each shell in ECALC should be smaller than default (200).
The various data control lines are identified by keywords. Only the
first 4 characters of a keyword are significant. The keywords can be in
any order, except END (if present) which must be last. Numbers and characters
in "[ ]" are optional. The only compulsory keyword is LABIN.
The available keywords are:
(optional) 80 character title to replace old title in MTZ file.
(COMPULSORY) This keyword defines which items are to be used in the calculation. The following <program label>s can be assigned:
EVAL PHI WT Example: LABI EVAL=EM_RE LABI EVAL=EM_RE PHI=AC WT=WTAC
(optional) This keyword allows the user to assign their own labels to the extra labels in the output file. All labels in LABIN will automatically be in the output file. The following <program label>s can be assigned:
PHI1 WT1 PHI2 WT2 PHI3 WT3 PHI4 WT4 PHI5 WT5 Example: LABO PHI1=NEWPHASE1 WT1=NEWWT1 - PHI2=NEWPHASE2 WT2=NEWWT2 - PHI3=NEWPHASE3 WT3=NEWWT3
In cases where the "known" phases are more than 80% of the number of large E values, only one set of refined phases will be output. So only PHI1 and WT1 can be assigned by LABOUT or do not assign any labels if the number of "known" phases is unknown and then PHI1 and WT1 will be in the output file.
(optional) The weights of three figures of merit for calculating the
combined figure of merit; the programme will normalize the values to obtain
wabs + wpsi + wres = 1.0. If small E values to calculate PSIZERO are not
reliable, a lower value can be given to wpsi.
Example: WFOM ABS 0.3 PSI 0.1 RES 0.6
(optional) The maximum E value to be used in RANTAN. This can be used
to exclude particularly large E values.
Example: EMAX 4.5
(optional) The minimum E value to be used in RANTAN.
Example: EMIN 1.0
(optional) The maximum E value to be used to calculate PSIZERO figure
Example: EPSI 0.1
(optional) The minimum KAPPA value for a triplet to be used in RANTAN.
Example: KMIN 1.0
(optional) The maximum KAPPA value for a triplet to be used in RANTAN.
Example: KMAX 20.0
(optional) The resolution range of E values from <res1> to <res2>
used in RANTAN.
Example: RESO 10.0 3.5 or RESO 3.5 10.0
(optional) The number of sets of random phases (number of trials). The
maximum number is 2000.
Example: MAXS 200
(optional) Print out full details about running RANTAN.
(optional) The number of random phases to be assigned to the starting
set (size of starting set).
Example: NRAN 600
(optional) The number of large E values to be used in RANTAN. The maximum
number is to keep <nref> + <nzro> less than 2000.
Example: NREF 800
(optional) The number of small E values to be used to calculate PSIZERO.
Normally default value is large enough.
Example: NZRO 50
(optional) The particular set number assigned by user to be refined
and output. User can use this keyword to investigate any set of phases
and maps after the first run of RANTAN. The number must be given in accretion
order. The maximum number of sets assigned by user is 5.
Example: NSET 4 39 199 250
(optional) The number of the best refined phase sets to be output. The
maximum number is 5.
Example: NOUT 5
(optional) The first <skip> phase sets will be skipped and RANTAN
starts from set <skip>+1.
Example: SKIP 500
(optional) The weight for a random phase. Higher weights can be used
if known phases are used or the first run of RANTAN was not successful.
Example: WMIN 0.45
(optional) The weight for a triplet; the value depends on the number
and type of atoms in the unit cell.
Example: WTRI 0.2
(optional) There are two procedures in RANTAN to refine random phases:
a fast procedure called FASTAN and a statistical weighting tangent formula
called SWTR which should be used when most of the ABS figures of merit
are greater than 1.3.
of input. If present, this must be the last keyword.
The input files are the keyword file and a standard MTZ reflection data
Here are the definitions for each label:
Name Item H, K, L Miller indices. EVAL E values (normalized structure factors). PHI Known phases. WT Weights of known phases. PHI1 New phases of the best set 1. WT1 Weights for the new phases of the best set 1. PHI2 New phases of the best set 2. WT2 Weights for the new phases of the best set 2. PHI3 New phases of the best set 3. WT3 Weights for the new phases of the best set 3. PHI4 New phases of the best set 4. WT4 Weights for the new phases of the best set 4. PHI5 New phases of the best set 5. WT5 Weights for the new phases of the best set 5.
The program output starts with details from the input keyword data lines. Then information from the input MTZ file follows. An error message will be printed out if any illegal input in the keyword data lines has been found and the program will stop.
The full details of running RANTAN will be printed out if the keyword LIST is given and that will include all the E values, the convergence map and figures of merit for each of the MAXS phase sets. Otherwise E values and convergence map will not be printed out and the figures of merit for the phase sets will be printed out only if the combined figure of merit is greater than 0.6. If a refined phase set is similar to a previous phase set, it will be flagged as such.
The best NOUT phase sets, as determined by the combined figures of merit, are then listed. Note that if the combined figures of merit are similar, then the phase sets may be related by an origin shift, symmetry operation and/or change of hand. Finally, details of the output MTZ file are listed, including the additional columns for the NOUT phase sets.
This example is to use E values after REVISE and ECALC:
rantan \ hklin $HOME/test.mtz \ hklout $SCRATCH/test-rantan.mtz \ << eof TITLE testing RANTAN. LABI EVAL=EM_RE LABO PHI1=NEWPHASE1 WT1=NEWT1 - PHI2=NEWPHASE2 WT2=NEWT2 RESO 10.0 3.5 END eof
This example is to use known phases with weights:
rantan \ hklin $HOME/test.mtz \ hklout $SCRATCH/test-rantan.mtz \ << eof TITLE testing RANTAN. LABI EVAL=EM_RE PHI=AC WT=WTAC RESO 10.0 3.5 NREF 800 WMIN 0.45 MAXS 100 NOUT 1 END eof