coordinate refinement and maps
Hi all, I am refining a protein with metal-ligand complexes. Is it possible to refine only y coordinates for an atom (on two fold) while keeping X and Z fixed using Phenix? Also is there a way to calculate something like anomalous difference-difference map (Anomalous Fobs - Anomalous Fcalc) to identify any additional atoms bound at metal sites. Thanks in advance for the help! Subhani
On Tue, Nov 20, 2012 at 12:41 PM, Subhani Bandara
I am refining a protein with metal-ligand complexes. Is it possible to refine only y coordinates for an atom (on two fold) while keeping X and Z fixed using Phenix? Also is there a way to calculate something like anomalous difference-difference map (Anomalous Fobs - Anomalous Fcalc) to identify any additional atoms bound at metal sites.
Not sure about the first question, but the answer to the second is yes, if you download the latest nightly build, phenix.refine is now able to output an anomalous log-likelihood gradient (LLG) map from Phaser, which will indicate where any unmodelled anomalous scattering is present. This is most useful if you use the group_anomalous strategy with any heavy atom selected (I would put S in this list), and I suspect you need to refine them separately for optimal results (i.e. each metal is its own group, rather than one group with the selection "element FE" or whatever it is). You can also get an LLG map from phenix.maps, but this simply guesses the anomalous scattering based on the wavelength, and will probably be noisier than if you refine f' and f''. -Nat
Hi all,
I am using Dev1223 and need to generate LLG map from phenix.refine to see
any additional anomalous scattering is there. In the output window of
phenix.refine I added LLG map to map coefficients and checked write mtz
file... option. I thought the the mtz file with LLG map will be written to
the output folder of refinement where the other files are, but don't see
any additional files generated other than usual files. Am I doing something
wrong?
Thanks in advance for any help
Subhani
On Tue, Nov 20, 2012 at 2:47 PM, Nathaniel Echols
On Tue, Nov 20, 2012 at 12:41 PM, Subhani Bandara
wrote: I am refining a protein with metal-ligand complexes. Is it possible to refine only y coordinates for an atom (on two fold) while keeping X and Z fixed using Phenix? Also is there a way to calculate something like anomalous difference-difference map (Anomalous Fobs - Anomalous Fcalc) to identify any additional atoms bound at metal sites.
Not sure about the first question, but the answer to the second is yes, if you download the latest nightly build, phenix.refine is now able to output an anomalous log-likelihood gradient (LLG) map from Phaser, which will indicate where any unmodelled anomalous scattering is present. This is most useful if you use the group_anomalous strategy with any heavy atom selected (I would put S in this list), and I suspect you need to refine them separately for optimal results (i.e. each metal is its own group, rather than one group with the selection "element FE" or whatever it is). You can also get an LLG map from phenix.maps, but this simply guesses the anomalous scattering based on the wavelength, and will probably be noisier than if you refine f' and f''.
-Nat _______________________________________________ phenixbb mailing list [email protected] http://phenix-online.org/mailman/listinfo/phenixbb
On Tue, Nov 27, 2012 at 12:03 PM, Subhani Bandara
I am using Dev1223 and need to generate LLG map from phenix.refine to see any additional anomalous scattering is there. In the output window of phenix.refine I added LLG map to map coefficients and checked write mtz file... option. I thought the the mtz file with LLG map will be written to the output folder of refinement where the other files are, but don't see any additional files generated other than usual files. Am I doing something wrong?
No, the LLG map coefficients should be part of the same MTZ file that all of the other map coefficients are written. At present I don't think they will be automatically opened in Coot when launched from the Phenix GUI (I will look into fixing this), nor will the "Auto-open MTZ" function in Coot recognize them. Instead, you need to select "Open MTZ, mmCIF, fcf, or phs" in Coot, pick the MTZ file, and once you get to the map setup dialog, choose "LLG" and "PHLLG" or whatever you decided to name the columns, and check "Is a difference map?". Randy's recommendation was to only look at peaks greater than the maximum negative value, so I would scroll up the contour level until all of the negative LLG density disappears. -Nat
Hi Subhani,
I am refining a protein with metal-ligand complexes. Is it possible to refine only y coordinates for an atom (on two fold) while keeping X and Z fixed using Phenix?
it's taken care of automatically by phenix.refine if atom in question is close enough to the special position in the starting model. If I recall it right, "close enough" means at least 0.5A or so.
Also is there a way to calculate something like anomalous difference-difference map (Anomalous Fobs - Anomalous Fcalc) to identify any additional atoms bound at metal sites.
If you refine against anomalous data set (containing Fobs+ and Fobs-) then traditional anomalous difference map will be output by phenix.refine by default. Recent versions should have the ability to create LLG maps as well. Pavel
On Tue, Nov 20, 2012 at 12:59 PM, Pavel Afonine
Also is there a way to calculate something like anomalous difference-difference map (Anomalous Fobs - Anomalous Fcalc) to identify any additional atoms bound at metal sites.
If you refine against anomalous data set (containing Fobs+ and Fobs-) then traditional anomalous difference map will be output by phenix.refine by default. Recent versions should have the ability to create LLG maps as well.
Which is *not* the same thing - the anomalous difference map Phenix outputs only shows the anomalous differences in F-obs, and not the difference between F-obs and F-calc. As a result, any weaker anomalous scatterers (like chlorine, etc.) may have their signal drowned out by the contribution of the metals. -Nat
Hello all, I have a question about the parameter definition for refinement groups (hope I picked the right term here). How does the definition and handling of refinement groups vary from the "refine.sites.rigid_body" scope to the "refine.adp.anisotropic" scope? For instance: refine { strategy = *individual_sites individual_sites_real_space *rigid_body \ *individual_adp group_adp tls *occupancies group_anomalous sites { individual = None torsion_angles = None rigid_body = chain A rigid_body = chain B } adp { individual { isotropic = None anisotropic = chain A anisotropic = chain B } would refine chains A and B as separate rigid groups, whereas only chain B would be refined anisotropically. Is this an intended behavior? BTW "anisotropic = chain A or chain B" refines both chains as expected. Cheers, Carsten
Hi Carsten, some keywords have type "multiple" and some not. In your example, rigid_body has type multiple, that is you can specify as many of them as you want: rigid_body = chain A rigid_body = chain B rigid_body = chain C and that means you will be refining three rigid bodies. Same applied to tls, and many others. anisotropic is not multiple, so it can be only one. I recall I had reasons to make it this way when implementing it but it was long long time ago, so I forgot what it was. To see all attributes for all parameters: phenix.refine --show-defaults=all.all which will yield a long hard to digest list. Pavel On 11/20/12 6:25 PM, Schubert, Carsten [JRDUS] wrote:
Hello all,
I have a question about the parameter definition for refinement groups (hope I picked the right term here). How does the definition and handling of refinement groups vary from the "refine.sites.rigid_body" scope to the "refine.adp.anisotropic" scope? For instance:
refine { strategy = *individual_sites individual_sites_real_space *rigid_body \ *individual_adp group_adp tls *occupancies group_anomalous sites { individual = None torsion_angles = None rigid_body = chain A rigid_body = chain B } adp { individual { isotropic = None anisotropic = chain A anisotropic = chain B
}
would refine chains A and B as separate rigid groups, whereas only chain B would be refined anisotropically. Is this an intended behavior?
BTW "anisotropic = chain A or chain B" refines both chains as expected.
Cheers,
Carsten
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Dear all, I ran "phenix.explore_metric_symmetry" with the command: phenix.explore_metric_symmetry --unit_cell="97,97,225,78,78,68" --space_group=P1 It output: ... ------------------------- Transforming point groups ------------------------- From P 1 to C 1 2 1 (x-y,x+y,z) using : * -k,-h,-l ... I understand that going from P1 to C2, one needs to apply the transformation matrix (x-y, x+y,z) on the P1 cell to form the C2 cell, and (-k, -h, -l) on the reflections. Naive question: why aren't the two matrices similar? The reciprocal space is the fourier transform of the real space; i was thinking that a reorientation matrix in the real space would be kept in the reciprocal space. My maths are not that good, and in P1 it is more complex than other space groups. Can someone tell me why the matrices are different? Also, in C2 there is a 2-fold axis parallel to b, so reflections (h,k,l) are equivalent to (-h, k, -l). In P1, they are not. Applying the above transformation matrix on the reflections would give (hP1, kP1, lP1) transforms into (-kP1, -hP1, -lP1), and these are equivalent to (kP1, -hP1, lP1)? Is this correct? thank you vincent
Hi Vincent,
The output you show has the following meaning:
The reindexing of the miller indices of (-k,-h,-l) of the P1 data gives you
data in the space group "C 1 2 1 (x-y,x+y,z)". This is a special (no
lattice translations) version of C2 that can be set to the standard setting
by applying the transformation (x-y,x+y,z) to the cell. This will
subsequently reindex your miller indices as well.
The "C 1 2 1 (x-y,x+y,z) " is a full space group. The change of basis
matrix stuck at the back of the standard symbol indicates which
transformation is required to get it back to the traditional setting.
INstead of specifying it in x,y,z, you can also make specify the COB on the
unit cell basis vectors. This allows you to do fun things like P1 (2a,b,c)
to describe the space group P1 with added operator (x+1/2,y,z), i.e. if you
would incorrectly index your data.
If you go here:
http://cci.lbl.gov/cctbx/explore_symmetry.html
and fill out the space group C 1 2 1 (x-y,x+y,z) you get this info
List of symmetry operations:
MatrixRotation-part typeAxis directionScrew/glide componentOrigin shiftx,y,z
1----y,-x,-z2[-1,1,0]0,0,00,0,0
i.e.
your two-fold axis lies in the xy plane.
I'll contact you off-list with more info.
P
On 21 November 2012 08:50, vincent Chaptal
Dear all,
I ran "phenix.explore_metric_**symmetry" with the command:
phenix.explore_metric_symmetry --unit_cell="97,97,225,78,78,**68" --space_group=P1
It output: ... ------------------------- Transforming point groups ------------------------- From P 1 to C 1 2 1 (x-y,x+y,z) using : * -k,-h,-l ...
I understand that going from P1 to C2, one needs to apply the transformation matrix (x-y, x+y,z) on the P1 cell to form the C2 cell, and (-k, -h, -l) on the reflections.
Naive question: why aren't the two matrices similar? The reciprocal space is the fourier transform of the real space; i was thinking that a reorientation matrix in the real space would be kept in the reciprocal space. My maths are not that good, and in P1 it is more complex than other space groups. Can someone tell me why the matrices are different?
Also, in C2 there is a 2-fold axis parallel to b, so reflections (h,k,l) are equivalent to (-h, k, -l). In P1, they are not. Applying the above transformation matrix on the reflections would give (hP1, kP1, lP1) transforms into (-kP1, -hP1, -lP1), and these are equivalent to (kP1, -hP1, lP1)? Is this correct?
thank you vincent ______________________________**_________________ phenixbb mailing list [email protected] http://phenix-online.org/**mailman/listinfo/phenixbbhttp://phenix-online.org/mailman/listinfo/phenixbb
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participants (6)
-
Nathaniel Echols
-
Pavel Afonine
-
Peter Zwart
-
Schubert, Carsten [JRDUS]
-
Subhani Bandara
-
vincent Chaptal