The engineering of membrane-permeable peptides.

Reversible lipid attachment was investigated as a means to deliver small peptides into cells. Two labile straight chain alkyl motifs were developed: a cysteine dodecane disulfide (Cdd) building block and a tyrosine- or serine-myristate ester. Both moieties are cleaved on cell internalization and are compatible with Fmoc solid phase peptide synthesis. A series of fluorophore-labeled peptides that varied in lipophilic content, net charge, and charge distribution were synthesized. The peptides were screened for cellular uptake efficiency as monitored by fluorescence microscopy. Effective peptide transport is based on a distributed net positive charge introduced as lysine residues at the C and/or N terminus of the peptide and the presence of a hydrophobic domain exhibiting an estimated log P4.0. The incorporation of labile lipid motifs into peptides enhances lipophilic character of the peptides and contributes to cellular uptake with minimal alteration to the native sequence.