PHOSPHOLIPID MEMBRANE-PERMEABILITY OF PEPTIDE NUCLEIC-ACID

Phospholipid vesicles (liposomes) as membrane models have been used to study the penetration properties of peptide nucleic acid (PNA), a new DNA analog in which the nucleobases are attached to a pseudo-peptide backbone, The liposomes were characterised by carboxyfluorescein efflu x, light-scattering and cryogenic transmission electron microscopy. Th e liposome structure was found not to be affected by the incorporation of PNA or an oligonucleotide. Two 10-mer fluorescein-labelled PNAs we re found to have low efflux rates (half-times of 5.5 and 11 days), com parable to a 10-mer oligonucleotide (half-time of 7 days). We conclude that passive diffusion of unmodified PNA is not an effective way of t ransport into biological cells.