Editing Property Selectors (section)

===Alternate Locations===
====Select All Alternate Locations====
*To select '''all''' residues with alternate locations (alt, alt loc), simply do:
<source lang="python">
select aa, not alt ""
</source>
Try it on 1CBN.

====Select All Alternate Locations Except the A-Locations====
* To select and remove all atoms with alternate locations (ALT, alt loc) that aren't the '''A''' record try the following.  This removes all alt locations that are not the original '''A''' location.  For example given the following pdb record,
<source lang="python" line="1">
ATOM    949  N   ARG A 124       6.039   8.484   9.313  1.00  9.82           N
ATOM    950  CA  ARG A 124       5.839   7.071   8.980  1.00 10.05           C
ATOM    951  C   ARG A 124       6.009   6.809   7.493  1.00  9.18           C
ATOM    952  O   ARG A 124       5.803   7.715   6.648  1.00  9.06           O
ATOM    953  CB  ARG A 124       4.437   6.660   9.425  1.00 10.61           C
ATOM    954  CG AARG A 124       4.381   6.539  10.955  0.50 12.54           C
ATOM    955  CG BARG A 124       4.170   6.743  10.930  0.50 14.58           C
ATOM    956  CD AARG A 124       2.996   6.418  11.561  0.50 11.86           C
ATOM    957  CD BARG A 124       2.700   7.091  11.242  0.50 17.41           C
ATOM    958  NE AARG A 124       2.110   7.506  11.144  0.50 13.01           N
ATOM    959  NE BARG A 124       2.229   6.746  12.588  0.50 19.94           N
ATOM    960  CZ AARG A 124       0.912   7.729  11.654  0.50 12.21           C
ATOM    961  CZ BARG A 124       2.123   5.510  13.067  0.50 21.42           C
ATOM    962  NH1AARG A 124       0.433   6.958  12.627  0.50 12.93           N
ATOM    963  NH1BARG A 124       2.470   4.470  12.319  0.50 24.35           N
ATOM    964  NH2AARG A 124       0.185   8.735  11.188  0.50 11.89           N
ATOM    965  NH2BARG A 124       1.658   5.310  14.313  0.50 18.28           N
</source>
the command below will remove the (not A so) B-locations (lines 7, 9, 11, 13, 15, 17).
<source lang="python">
# select & remove all non A altlocs
remove not (alt ''+A)
# reset the PDB information
alter all, alt=''
</source>

See also, [[removeAlt]] for a script to do this for you.