# Difference between revisions of "ColorByRMSD"

## Introduction

This script allows you to color two structures by Root Mean Square Deviation (RMSD), as calculated by PyMol's internal Rms_Cur command. The pairwise, C-alpha, RMSD is calculated only between those residues which are first used by PyMol's internal Super command to superpose the two structures. The RMSD values are stored as B-factors of these residues, which are colored by a rainbow color spectrum, with blue specifying the minimum pairwise RMSD and red indicating the maximum. Residues NOT used by Super for RMSD calculation are colored white.

## Code

Please use this script with the option doPretty=T to gain the most benefit. Additionally, setting Cartoon representation to loop, with the command:

``` cartoon loop </script> may help ease comparisons. Do keep in mind, all original B-factors values are overwritten!

==== Examples ====
<source lang="python">
# example #1
colorByRMSD 1cbs, 1hmt, doAlign=T, doPretty=T
# example #2
colorByRMSD 1eaz, 1fao, doAlign=T, doPretty=T
```
```"""
--- ColorByRMSD: RMSD based coloring ---
Authors : Shivender Shandilya; Jason Vertrees
Program : ColorByRMSD
Date    : July 2009
Version : 0.1.0 (first release!)
Mail    : firstname.lastname@umassmed.edu

Keywords: color rms rmsd colorbyrms colorbyrmsd
----------------------------------------------------------------------
Reference:
This email from Warren - http://www.mail-archive.com/pymol-users@lists.sourceforge.net/msg07078.html
Literature:
DeLano, W.L. The PyMOL Molecular Graphics System (2002) DeLano Scientific, San Carlos, CA, USA. http://www.pymol.org
----------------------------------------------------------------------
"""

import pymol
import cmd
from pymol import stored

def strTrue(p):
return p[0].upper() == "T"

# The main function that assigns current RMSD as the new B-factor
def rmsUpdateB(objA, alnAri, objB, alnBri):
for x in range(len(alnAri)):
s1 = objA + " and n. CA and i. " + alnAri[x]
s2 = objB + " and n. CA and i. " + alnBri[x]
rmsd = cmd.rms_cur(s1, s2, matchmaker=4)
cmd.alter( s1, "b = " + str(rmsd))
cmd.alter( s2, "b = " + str(rmsd))
cmd.sort(objA); cmd.sort(objB)

def colorByRMSD(objSel1, objSel2, doAlign="True", doPretty=None):
"""
colorByRMSD -- align two structures and show the structural deviations
in color to more easily see variable regions.

PARAMS

objSel1 (valid PyMOL object or selection)
The first object to align.

objSel2 (valid PyMOL object or selection)
The second object to align

doAlign (boolean, either True or False)
Should this script align your proteins or just leave them as is?
If doAlign=True then your original proteins are aligned.
If False, then they are not. Regardless, the B-factors are changed.
DEFAULT: True

doPretty (boolean, either True or False)
If doPretty=True then a simple representation is created to
highlight the differences.  If False, then no changes are made.
DEFAULT: False

RETURNS
None.

SIDE-EFFECTS
Modifies the B-factor columns in your original structures.

"""
# First create backup copies; names starting with __ (underscores) are
# normally hidden by PyMOL
tObj1, tObj2, aln = "__tempObj1", "__tempObj2", "__aln"

if strTrue(doAlign):
# perform the alignment
cmd.create( tObj1, objSel1 )
cmd.create( tObj2, objSel2 )
cmd.super( tObj1, tObj2, object=aln )
cmd.matrix_copy(tObj1, objSel1)
else:
# perform the alignment
cmd.create( tObj1, objSel1 )
cmd.create( tObj2, objSel2 )
cmd.super( tObj1, tObj2, object=aln )

# Modify the B-factor columns of the original objects,
# in order to identify the residues NOT used for alignment, later on
cmd.alter( objSel1 + " or " + objSel2, "b=-10")
cmd.alter( tObj1 + " or " + tObj2, "chain='A'")
cmd.alter( tObj1 + " or " + tObj2, "segi='A'")

# Update pymol internal representations; one of these should do the trick
cmd.refresh(); cmd.rebuild(); cmd.sort(tObj1); cmd.sort(tObj2)

#  Create lists for storage
stored.alnAres, stored.alnBres = [], []

#  Get the residue identifiers from the alignment object "aln"
cmd.iterate(tObj1 + " and n. CA and " + aln, "stored.alnAres.append(resi)")
cmd.iterate(tObj2 + " and n. CA and " + aln, "stored.alnBres.append(resi)")

# Change the B-factors for EACH object
rmsUpdateB(tObj1,stored.alnAres,tObj2,stored.alnBres)

# Store the NEW B-factors
stored.alnAnb, stored.alnBnb = [], []
cmd.iterate(tObj1 + " and n. CA and " + aln, "stored.alnAnb.append(b)" )
cmd.iterate(tObj2 + " and n. CA and " + aln, "stored.alnBnb.append(b)" )

# Get rid of all intermediate objects and clean up
cmd.delete(tObj1)
cmd.delete(tObj2)
cmd.delete(aln)

# Assign the just stored NEW B-factors to the original objects
for x in range(len(stored.alnAres)):
cmd.alter(objSel1 + " and n. CA and i. " + str(stored.alnAres[x]), "b = " + str(stored.alnAnb[x]))
for x in range(len(stored.alnBres)):
cmd.alter(objSel2 + " and n. CA and i. " + str(stored.alnBres[x]), "b = " + str(stored.alnBnb[x]))
cmd.rebuild(); cmd.refresh(); cmd.sort(objSel1); cmd.sort(objSel2)

if doPretty!=None:
# Showcase what we did
cmd.orient()
cmd.hide("all")
cmd.show_as("cartoon", objSel1 + " or " + objSel2)
# Select the residues not used for alignment; they still have their B-factors as "-10"
cmd.select("notUsedForAln", "b < 0")
# White-wash the residues not used for alignment
cmd.color("white", "notUsedForAln")
# Color the residues used for alignment according to their B-factors (RMSD values)
cmd.spectrum("b", 'rainbow',  "((" + objSel1 + " and n. CA) or (n. CA and " + objSel2 +" )) and not notUsedForAln")
# Delete the selection of atoms not used for alignment
# If you would like to keep this selection intact,
# just comment "cmd.delete" line and
# uncomment the "cmd.disable" line below.
cmd.delete("notUsedForAln")
# cmd.disable("notUsedForAln")

print "\nColorByRMSD completed successfully.\nObjects are now colored by C-alpha RMS deviation.\n"

cmd.extend("colorByRMSD", colorByRMSD)
```