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Symmetry Expansion

Next is shown how to use Overlay to expand a structure by crystallographic symmetry. The example is the Bacteriochlorophyll-a containing protein which exists as a trimer but the asymmetric unit is a monomer. Sometimes it is useful to expand the coordinates out to the full trimer.

$tntbin/overlay << $eof
CELL 111.9 111.9 98.3 90 90 120
TRANSFORMATION three-fold OPERATOR -Y+1, X-Y, Z
INCLUDE bcl_phase7r.cor
RENAME CHAIN NULL  TO A

COPY    A|      B|
APPLY   B|

COPY    B|      C|
APPLY   C|

PUNCH test.cor ATOMC
$eof
if ($status >< 0) then exit 1

The symmetry operator and the coordinates are read. Just to clean up the appearance of the final coordinate file the original nameless chain is renamed to A. Then chain A is copied to B and B is transformed. Then B is copied to C and it too is transformed by the same operator. C, having been transformed twice, is now right where we want it.



Dale Edwin Tronrud
Thu Jul 6 23:24:57 PDT 2000