Abstract: Permeable Switch Region I and II peptides in the range of 9 to 25 amino acid residues in length are provided for specifically inhibiting signaling through G? subunits. In addition, compositions and methods for inhibiting platelet aggregation and ?11b?3 integrin activation using the Switch Region I and II peptides are provided.

Abstract: The invention allows the generation and screening of a large population of peptides for the presence of peptides which bind a particular macromolecule or macromolecular complex with high affinity, and further allows the favored net synthesis of analyzable quantities of such peptides, by using as the "trap" a macromolecule or macromolecular complex for which binding of the peptide is desired. The starting mixture is preferably spiked with a peptide having some affinity for the target macromolecule so that mutation of the spike or "lead" peptide is favored. The development of improved binding peptides through scrambling may be dynamically monitored by initially binding the target with an insolubilized ligand, and then looking for an increase in the concentration of the target in the soluble phase as a result of the displacement of the reference ligand by scrambled peptides.