  In the framework of the polymer reference interaction site model (PRISM)
extended to incorporate the centers of mass (CM) of the groups of monomers
constitutive of the macromolecules as auxiliary sites, a general relationship
between the monomer-monomer and CM-CM pair correlation functions is derived for
arbitrary mixtures of macromolecules of arbitrary structure. It extends
previous results for homopolymer fluids and should be useful to develop
semi-analytic coarse-grained descriptions of complex fluids.
