please do

# The following script is a demonstration of how to
# manipulate selections to do a command
# functionnally equivalent to "Select Groups Close to
# another chain" of the Select menu.
# It is slower, but more flexible because you
# can choose the two chains concerned.


open pdb from download "4MDH.pdb"; 

$SELA = select in "4mdh" chain "A";
$SELB = select in "4mdh" chain "B";
color res of $SELA in red;
color res of $SELB in blue;
center on visible;

$SEL1 = select within 4.0 of $SELA;
$SEL2 = select within 4.0 of $SELB;

# as there is no "AND" (union) function we need
# to do this trick.

$SELA = $SEL1 - $SELA;
$SELB = $SEL2 - $SELB;
$SEL = $SELA + $SELB;

select $SEL;
show res,side of $SEL;

thank you


