Bridged β3-Peptide Inhibitors of p53-hDM2 Complexation: Correlation between Affinity and Cell Permeability

beta-peptides possess several features that are desirable in peptidomimetics: they are easily synthesized, fold into stable secondary structures in physiologic buffers, and resist proteolysis. They can also bind to a diverse array of proteins to inhibit their Interactions with alpha-helical ligands. beta-peptides are usually not cell-permeable, however, and this feature limits their utility as research tools and potential therapeutics. Appending an Arg(8) sequence to a beta-peptide improves Uptake but adds considerable mass. We previously reported that embedding, a small cationic patch within a PPII, alpha-, or beta-peptide helix improves uptake without the addition of significant mass. In another mass-neutral strategy, Verdine, Walensky, and others have reported that insertion of a hydrocarbon bridge between the i and i + 4 positions of an alpha-helix also increases cell Uptake. Here we describe a series of beta-peptides containing diether and hydrocarbon bridges and compare them on the basis of cell uptake and localization, affinities for hDM2, and 14-helix structure. Our results highlight the relative merits of the cationic-patch and hydrophobic-bridge strategies for improving beta-peptide Uptake and identify a surprising correlation between uptake efficiency and hDM2 affinity.