Preferred Label : line repetition groups;
IUPAC definition : The possible symmetries of arrays extending in one direction with a fixed repeating
distance. linear polymer chains in the crystalline state must belong to one of the
line repetition groups. Permitted symmetry elements are: the identity operation (symbol
l); the translation along the chain axis (symbol t); the mirror plane orthogonal to
the chain axis (symbol m) and that containing the chain axis (symbol d); the glide
plane containing the chain axis (symbol c); the inversion centre, placed on the chain
axis (symbol i); the two-fold axis orthogonal to the chain axis (symbol 2); the helical,
or screw, symmetry where the axis of the helix coincides with the chain axis. In the
latter case, the symbol is s A * M / N, where s stands for the screw axis, A is the
class of the helix, * and / are separators, and M is the integral number of residues
contained in N turns, corresponding to the identity period (M and N must be prime
to each other). The class index A may be dropped if deemed unnecessary, so that the
helix may also be simply denoted as s M / N.;
Origin ID : L03564;
See also
The possible symmetries of arrays extending in one direction with a fixed repeating
distance. linear polymer chains in the crystalline state must belong to one of the
line repetition groups. Permitted symmetry elements are: the identity operation (symbol
l); the translation along the chain axis (symbol t); the mirror plane orthogonal to
the chain axis (symbol m) and that containing the chain axis (symbol d); the glide
plane containing the chain axis (symbol c); the inversion centre, placed on the chain
axis (symbol i); the two-fold axis orthogonal to the chain axis (symbol 2); the helical,
or screw, symmetry where the axis of the helix coincides with the chain axis. In the
latter case, the symbol is s A * M / N, where s stands for the screw axis, A is the
class of the helix, * and / are separators, and M is the integral number of residues
contained in N turns, corresponding to the identity period (M and N must be prime
to each other). The class index A may be dropped if deemed unnecessary, so that the
helix may also be simply denoted as s M / N.