Low-molecular-weight synthetic molecules that mimic the activity of na
tive biological macromolecules have therapeutic potential, utility in
large-scale production of biopharmaceuticals, and the capacity to act
as probes to study molecular recognition events. We have developed a n
onpeptidyl mimic for Staphylococcus aureus Protein A (SpA). The specif
ic recognition and complexation elements between the B domain (Fb) of
SpA and the Fc fragment of IgG were identified from the x-ray crystall
ographic structure, Computer-aided molecular modeling was used to desi
gn a series of biomimetic molecules around the Phe132-Tyr133 dipeptide
involved in its binding to IgG. One of the ligands binds IgG competit
ively with SpA in solution and when immobilized on agarose beads, with
an affinity constant of 10(5)-10(6) M-1. The immobilized artificial P
rotein A was used to purify IgG from human plasma and murine IgG from
ascites fluid, and to remove bovine IgG from fetal calf serum.