There is no relationship between ACT and PyMOL, so one wouldn't necessarily expect them to match in terms of how they name the resulting objects.  However, I suspect there may also be a difference of intent:

Based on a quick glance at PyMOL source code, PyMOL appears to convey a relative cell translation (based on centers of geometries), whereas ACT may be returning the computation formula.

In other words, PyMOL attempts to inform the user as to whether the generated symmetry-related atom selection is within the same cell as the query selection or in one of the adjacent cells (in a translational sense).  Thus in PyMOL, the (overall) nearest mates (with respect to the center of geometry) will usually have a translation of 00 00 00, and most of the time, nearby mates will vary +1 or -1 along a single translation.

I'm guessing ACT simply provides the symmetry operator and the effective translation applied to generate the nearby mate.  That's useful for recomputing the mate later on, but it doesn't tell the user anything about proximity.  PyMOL's approach is unhelpful for recomputing a mate, but one can tell from the object name alone which objects are likely to have the most extensive contacts and how they relate in a relative sense (with respect to cell translations away from the query selection).

Perhaps PyMOL could provide ACT-like naming through an optional setting?


-----Original Message-----
From: []
Sent: Thu 9/17/2009 4:52 PM
Subject: [PyMOL] Pymol Symmetry Mates Naming


I am encountering a problem with symmetry mates generated by pymol. It
seems that the naming system in pymol and ccp4-supported ACT program are
not consistent. I have tested several pdbs in P4212 space group and
attempted to figure out the relationship between these two, but failed. I
appreciate it if you could hint me out.

Some comparisons are listed below.

ACT:NSYM ( number of symmetry operation) followed by number of
translations of one unit cell along x,y,z.

PYMOL: the first two digits are the symmetry operation. The next six
digits correspond to the relative integral unit cell translation xxyyzz.

I figured that the symmetry operation( the first two digits in pymol) is
off by 1 compared to the first digit in ACT, but have no idea how the last
six digits relates to the ACT


pymol        ACT
01000000     21-10
02000000     3220
03000000     4010
05000000     6000
05000001     6001
pymol       ACT
000000-1    100-1
03000000    4000
01000000    20-10


01000000   21-10
00000001   1001
030000-1   401-1
070000-1   8110
07000000   8111
03000000   4010


Fang Sheng

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