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REFMAC (CCP4: Supported Program)

User's manual for the program refmac_5.0.36

Keyworded input - Restraints keywords

Anything input on a line after "!" or "#" is ignored and lines can be continued by using a minus (-) sign. The program only checks the first 4 characters of each keyword. The order of the cards is not important except that an END card must be last. Some keywords have various subsidiary keywords. The available keywords in this section are:

ANGLe
Restraints on bond angles
BFACtor/TEMPerature
Restraints on B values
CHIRal_volumes
Restraints on chiral volumes
DISTance
Restraints on bond distances
HOLD
Restraints against excessive shifts
MAKE_restraints
Controls making restraints and checking coordinates against dictionary
NCSR/NONX
Restraints on non-crystallographic symmetry
PLANe
Restraints on planarity
RBONd
Rigid bond restraints on the anisotropic B values of bonded atoms
SPHEricity
Sphericity restraints on the anisotropic B values
TORSION
Restraints on the torsion angles
VDWR/VAND
Restraints on VDW repulsions

These keywords are used to create restraints and to set the weighting of the restraints.

MAKE_restraints [HYDR Y|N|A] [HOUT Y|N] [CHECk Y|N] [BUIL Y|N] [FORM F|U] [PEPT Y|N] [LINK Y|N] [SUGAr Y|N|D]\ [CONNectivity Y|N|D] [SYMM Y|N] [CISP Y|N] [SS Y|N|D] [CHAIn Y|N] [NEWLigand Exit|Noexit] [VALUe COOR|ENER] [EXIT Y|N]

For full description including algorithms look MAKECIF"s documentation

This keyword controls the level of automatic restraint creation. REFMAC uses predefined dictionary entries. Any additional entry could be added using LIB_IN <file name> which contains a user's local ligand descriptions (see How to make new ligand dictionary?). On the basis of these files, the program makes intelligent suggestions on potential extra restraints. If additional user input is needed, the program stops, outputting information that should help the user to decide what to do next (e.g. a coarse picture of a ligand as the program 'understands' it, for the user to help in setting up any extra restraints).

Defaults:

MAKE HYDR All
MAKE HOUT No
MAKE CHEC No
MAKE BUIL No
MAKE FORM Unformatted
MAKE PEPT No
MAKE LINK No
MAKE SUGA Yes
MAKE SS   Yes
MAKE CISP Yes
MAKE SYMM No
MAKE CONN No
MAKE CHAIn Yes
MAKE NEWLigand Exit
MAKE VALUe ENERgy
MAKE EXIT No

Subkeywords:

HYDR [ Yes | No | All ] (Default HYDRogens All)
How to deal with the hydrogen atoms.
Y - if hydrogens are present in the input file, use them,
N - ignore hydrogens even if they are present in the input coordinate file,
A - add all hydrogens in their riding positions and use them for geometry and structure factor calculations. They also contribute to the gradient and second derivative matrix of geometry residual.
For low resolution and early stages it is better to use MAKE HYDR N, i.e. do not use hydrogens even if they are present in the input file.
HOUT [ Yes | No ] (Default HOUT N)
Whether to write hydrogens to the output coordinate file or not.
Y - write hydrogens to the output file,
N - do not write hydrogens to the output file.
CHECk [ ALL | LIGAnd | NONE ] (Default CHECk LIGAnd)
Whether to check amino acids in the input coordinate file against dictionary descriptions.
ALL - check all monomers against dictionary descriptions,
LIGAnd - do not check amino acids, DNA/RNA and standard sugars. In general monomers which are part of chain will not be checked. It is safe option to use.
NONE - do not check all monomers. In this case program relies on correctness of monomer and atom names in monomers. User has to be very careful in using this option.
BUILd [ Yes | No ] (Default BUILd N)
Whether to build absent atoms or not. For example, if you have ASN in input coordinates and OD1 and ND2 are absent, the program can try to find their position. Usually rebuilt atoms have occupancy 0.00, so they do not affect refinement.
Y - build absent atoms,
N - do not build absent atoms.
FORM [ Formatted | Unformatted ] (Default FORMat Unformatted)
Whether to use restraints file in Formatted or Unformatted form. If you want to examine the list of restraints then you could use:
MAKE FORM F
MAKE EXIT Y
In other cases unformatted form seems to be faster to handle.
PEPT [ Yes | No ] (Default PEPTide N)
Check and/or use presence of L or D peptides.
Y - check if peptide is L or D and use as they are,
N - check if there are D peptides but use standard L peptide descriptions.
LINK [ Yes | No | Define ] (Default LINK N)
Check and/or use links between different residues that are not involved in standard peptide links (i.e. connectivity that is not implied by the primary structure. Atoms involved in bonds between HET groups, or between a HET group and standard residues, as well as reduced peptide bonds can be described with this keyword).
Y - check and, if specified by record LINK in the input coordinate file, use links between residues. Links which have not been specified in the input coordinates but are found by the program, will be added to the list of links specified in the input coordinate file.
N - check links between residues and give information about them in the log file, but do not use them UNLESS they are specified by record LINK in the input coordinate file.
D - ignore links in the input coordinate file specified by record LINK. Check if current coordinates suggest links, and ONLY use those; i.e. let the program define what is a link and what is not.

In the early stages it is better to use LINK N. In later stages the user can use the following keywords to check if there are any links between residues which should be taken into account:

MAKE FORM F
MAKE LINK D
MAKE EXIT Y
MONItor MANY

After creation of restraints and checking all links, the program will stop. Then the user needs to examine the .log file, restraint file and the new library suggested by the program, to see if there is anything worthy of more attention.

Examples of a LINK record in a coordinate file:
         1         2         3         4         5         6         7
123456789012345678901234567890123456789012345678901234567890123456789012
LINK         O1  DDA     1                 C3  DDL     2
LINK        MN    MN   391                 OE2 GLU   217            2565
SUGAr [ Yes | No | Define ] (Default SUGAr Y)
Check and/or use links between sugars and sugar-protein links. These links can be specified through record LINK in coordinate files.
Y - check and, if specified by record LINK in the input coordinate file, use links between sugars and sugar-protein links. If sugar links are present in the input coordinate file they will have high priority.
N - check links between sugars and sugar-protein links and give information about them in the log file, but do not use them UNLESS they are specified by record LINK in the input coordinate file.
D - ignore sugar links in the input coordinate file specified by record LINK. Check if current coordinates suggest links, and ONLY use those; i.e. let the program define what is a suitable sugar link and what is not.
SSbridge [ Yes | No ] (Default SS Y)
Check and/or use disulphide bridges automatically.
Y - the program will find disulphide bridges and use restraints for them.
N - the program will check presence of disulphide bridges but ONLY use disulphide bridges if they are specified in the input coordinate file through record SSBOND.
CISP [ Yes | No ] (Default CISPeptide Y)
Check and/or use cis peptides automatically.
Y - find and use cis peptides automatically,
N - check but do not use cis peptides UNLESS they have been given specifically in the input coordinate file, through record CISPEP.
SYMM [ Yes | No ] (Default SYMM N)
Check and/or use links between symmetry related atoms.
Y - check the existence of links between symmetry related atoms and use if described explicitly,
N - do not use links between symmetry related atoms.
CONN [ Yes | No | Define ] (Default CONNectivity N)
Check connectivity between consecutive residues (e.g. standard peptide links and connectivity within a HET group).
Y - check and, if specified by record CONECT in the input coordinate file, use connectivity in polypeptides and DNA/RNA. Connectivity which is not specified in the input coordinates but is found by the program, will be added to the list of connectivity specified in the input coordinate file.
N - check connectivity between consecutive residues of polypeptide chain and DNA/RNA, but do not use them UNLESS they are specified by record CONECT in the input coordinate file. If consecutive residue numbers differ by more than two, it is assumed there is no link between them.
D - ignore connectivity in the input coordinate file specified by record CONECT. Check if coordinates suggest connectivity, and ONLY use those; i.e. let the program define what is connected and what is not.
CHAIn [ Yes | No ] (Default CHAIn N)
Check and/or use chain definition automatically.
Y - check chain definitions for peptide/DNA/RNA/sugar, cyclic peptide etc., and use if they are suggested by the coordinate file.
N - check but do not use chain definitions.
NEWLigand [ Exit | Noexit ] (Default NEWLigand Exit)
If the program encounters new ligand, it will stop and tell what to do next. If
MAKE NEWLigand Noexit
has been specified then the program will continue to work relying on the dictionary description it has created using coordinates and/or minimum description of this ligand. At the moment it is highly recommended to check entries created by the program and make sure that these correspond to the ligands the user wants.
VALUe [ COORdinates | ENERgy ] (Default VALUe ENERgy)
It tells to the program where to take the ideal values. If 'ENERgy' has been specified then ideal values will be taken from the energetic library. If 'COORdinates' has been specified then the program will take ideal values from the coordinates. If you want to take ideal values from the coordinates then make sure that coordinates have been derived using good energetic minimisers or they have been refined against very high resolution data.
EXIT [ Yes | No ] (Default EXIT N)
It tells the program to exit or not after creating restraints. It is useful when a new entry is added. Then the user could use following keywords:
MAKE FORM F
MAKE EXIT Y
Then look at the restraints file and check validity and values of the restraints.

DISTance <wdskal>

[Default 1.0]

<WDSKAL> is a multiplier used in calculating the weights for the distance restraints. The weights are of the form: Weight = (WDSKAL/ SIGD)2. Sigmas for bond distances come from the dictionary file.

ANGLe <angle_scale>

[Default 1.0]

<angle_scale> is multiplier used in calculating weights for the bond angle restraints. The weights have the form: Weight = (angle_scale/SIG_angle)2. SIG_angle comes from the dictionary file.

PLANe <wpskal>

[Default 1.0]

<WPSKAL> is a multiplier for the distance restraints defining planes. The weight used for the planes is (WPSKAL / SIGPlane)2. SIGPlane comes from the dictionary file.

CHIRal <wcskal>

[Default 1.0 0.15]

<WCSKAL> is used in weighting Chiral groups restraints. The weight used is (WCSKAL /SIGChiral)2. SIGChiral comes from the dictionary file.

TEMPerature | BFAC <wbskal> <sigb1> <sigb2> <sigb3> <sigb4>

or

TEMPerature | BFAC SET <B_value>

For example:

BFAC 1.0 1.5 2.0 3.0 4.5
BFACtor SET 20.0

[Default 1.0 2.0 4.0 4.0 6.0 ]

<WBSKAL> is used in calculating the weight for the temperature factor restraint parameters based on the types of bonding in which the atoms are involved. Weight calculated for B_value restraints is (WBSKAL/<sigbi>)**2.

<sigb1>
sigma for bonded atoms of the main chain
<sigb2>
for bonded atoms of the side chain
<sigb3>
for angle related atoms of main chain
<sigb4>
for angle related atoms of side chain

SET <B_value> - tells the program to set all B values to <B_value>

SPHEricity <sigsph>

[Default 2.0]

For example:

SPHEricity 5.0

<sigsph> is used to restrain atomic anisotropic tensor to be spherical. Used weight is calculated as 1.0/<sigsph>**2.

RBONd <sigrbond>

[Default 2.0 ]

For example:

RBONd 3.0

<sigrbond> is used to make minimum of projections of anisotropic tensors along bond for the bonded atoms. Used weight is calculated as 1.0/<sigrbond>**2.

NCSR [NCHAIN <nchains>] [CHAIns <chain_id_1>.....<chain_id_nchains>] [NSPAns <nspans> <residue_first_1> <residue_last_1> <ncode_1>..... <residue_first_nspans> <residue_last_nspans> <ncode_nspans>]

To define non-crystallographic symmetry. Previously part of PROTIN. Now moved to REFMAC.

For example:

NCSRestraints NCHAins 5 CHAIns A B C D E NSPANS 2 1 100 1 101 150 2

or

NCSR <wsscal> <sgsp1> <sigsp2> <sigsp3> <sigsb1> <sigsb2> <sigsb3>

Parameters for weighting of the contribution of the ncs restraints.

For example (they are default values):

NCSR 1.0 0.05 0.5 5.0 0.5 2.0 10.0

This keyword controls restraints on non-crystallographically related atoms. If the first value after NCSR is NCHAin, then the first option, i.e. definition of NCS restraints, is assumed. In this case, the following subkeywords are available:

NCHAIns <nchains>
Number of chains involved in this NCS restraint
CHAIns <chain_id_1>.....<chain_id_nchains>
Identifier of the chains involved in this NCS restraint. Number of chain identifiers should be equal to <nchains>.
NSPAns <nspans> <residue_first_1> <residue_last_1> <ncode_1>.....<residue_first_nspans> <residue_last_nspans> <ncode_nspans>
Number of pieces of chains which should be treated with different weighting schemes.
<nspans> is number of spans,
<residue_first_i><residue_last_i> are first, last residue numbers involved in i'th span, with i=1,nspans.
<ncode_i> is weighting to be used for i'th span, with i=1,nspans.
Codes for restraints are as follows:
ncode    Main_Chain       Side_Chain

1    tight restraint   tight restraint
2    tight restraint   medium restraint
3    tight restraint   loose restraint
4    medium restraint  medium restraint
5    medium restraint  loose restraint
6    loose restraint   loose restraint

If NCSR is followed only by numbers, these values are used for weighting of contribution of NCS restraints.

[Default 1.0 0.05 0.5 5.0 0.5 2.0 10.0]

<wsscal> is used in weighting restraints involving non-crystallographic symmetry. The weight is given by (<wsscal> / <sigs>)**2.

<sigsp1>, <sigsp2>, <sigsp3> are values associated with non-crystallographic positional restraints and are for tight, medium and loose restraints respectively.

<sigsb1>, <sigsb2>, <sigsb3> are values associated with non-crystallographic thermal restraints and are for tight, medium and loose restraints respectively.

TORSION <wtskal>

[Default 1.0]

For example:

TORSion 2.0

<wtskal> is a multiplier used in calculating the weights for the torsional angle restraints. The weight is of the form Weight = (<wtskal> / <SIGT>)**2, SIGT comes from dictionary files.

VANDerwaals (or VDWR or NONBonding) <wvskal>

or

VANDerwaal (or VDWR or NONBonding) [OVERall <wcskal>] [SIGMA VDW <vsigma > | HBONd <hsigma> | METAl <msigma> | TORSion <tsigma> DUMMy <dsigma> ] [INCRement TORSion <tincrement> | ADHB <adincrement> | AHHB <ahincrement> DUMMy <dincrement>]

[Default:

NONBonding OVERall 1.0
NONBonding SIGMa VDW 0.3
NONBonding SIGMa HBOND 0.5
NONBonding SIGMa METAl 0.5
NONBonding SIGMa TORSion 0.5
NONBonding SIGMa DUMMy   0.3
NONBonding INCRement TORSion -0.75
NONBonding INCRement ADHB    -0.2
NONBonding INCRement AHHB     0.2 
NONBonding INCRement DUMMy   -0.7 ]

This keywords controls parameters and weights of restraints on nonbonding interactions. REFMAC deals only with the repulsive part of nonbonding interactions, i.e. if separation of the atoms is larger than "ideal" then they are not considered to be interacting atoms.

The program excludes all atom pairs related by one covalent bond, angle, or if they are in the same plane. Atoms related by one torsion angle are treated separately.

OVERall <wvskal>
Controls overall weights on all nonbonding interactions.
SIGMa VDW <vsigma> | HBONd <hsigma> | METAl <msigma> | TORSion <tsigma> DUMMy <dsigma>
Controls sigmas for each type of nonbonding interactions.
VDW <vsigma>
sigma of atom pair involved in vdw repulsion
HBONd <hsigma>
sigma of atom pair potentially involved in hydrogen bonding interactions
METAl <msigma>
sigma of atom pair potentially involved in metal-ion interactions
TORSion <tsigma>
sigma of atom pair involved in vdw interactions and related by one torsion angle.
DUMMy <dsigma>
sigma of atom pair involved dummy and nondummy atoms.
INCRement TORSion <tincrement> | ADHB <adincrement> | AHHB <ahincrement>
Provides increment factors for different types of nonbonding interactions.
TORSion <tincrement>
If atoms are related by one torsion angle and they are closer than vdw1 + vdw2 + tincrement, then they are considered to be interacting atoms. Here vdw1 and vdw1 are vdw radii of the interacting atoms.
ADHB <adincrement>
If atoms can make hydrogen bond, i.e. one of them is a potential acceptor and the other is a potential donor and they are closer than vdw1 + vdw2 + adincrement, then they are considered to be interacting atoms. Here vdw1 and vdw2 are vdw radii of donor and acceptor.
AHHB <ahincrement>
If one of atoms is an acceptor and the other one a hydrogen from a donor and they are closer than vdw1 + ahincrement, then they are considered to be interacting atoms. Here vdw1 is vdw radius of the acceptor.
DUMMy <dincrement>
If on of atoms is dummy and another is nondummy and they are closer than vdw1 + vdw2 + dincrement, then they are considered as interacting atoms. Here vdw1 and vdw2 are vdw radii of atoms involved in the interaction.

HOLD <PBEL> <BDEL> <QDEL>

[Default 0.3 3.0 0.2]

Restraint to current values <PDEL> is a restraint on the magnitude of positional shifts. This goes into the matrix as (a/<PDEL>)**2, (b/<PDEL>)**2, (c/<PDEL>)**2 where a, b, c are the unit cell parameters.

<BDEL> is a shifts magnitude restraint on individual thermal parameters and goes into the matrix as (1/<BDEL>)**2. It is not used if ITEMP = 0.

<QDEL> is the shifts magnitude restraint on variable occupancy factors (not used if NOCC=0). This goes into the matrix as (1/<QDEL>)**2.

[See also keyword MONItor]