Dodecameric is a term pertaining to protein quaternary structure, and describes a protein complex with 12 protein subunits (protein chains). Dodecameric complexes can have a number of subunit 'topologies', but typically only a few of the theoretically possible subunit arrangements are observed in protein structures.
A dodecamer is a protein complex with 12 protein subunits.
A common subunit arrangement involves a tetrahedral distribution of subunit trimers (or 3-4-point symmetry). Another observed arrangement of subunits puts two rings of six subunits side by side along the six fold axis (or 2-6-point symmetry).