Protein transduction: unrestricted delivery into all cells?

Several proteins can traverse biological membranes through protein transduc tion. Small sections of these proteins (10-16 residues long;) are responsib le for this. Linking these domains covalently to compounds, peptides, antis ense peptide nucleic acids or 40-nm iron beads, or as in-frame fusions with full-length proteins, lets them enter any cell type in a receptor- and tra nsporter-independent fashion. Moreover, several of these fusions, introduce d into mice, were delivered to all tissues, even crossing the blood-brain b arrier. These domains thus might let us address new questions and evert hel p in the treatment of human disease.