We studied a number of physicochemical parameters of transfection-active peptide-DNA complexes including size, aggregation behaviour and circular dichroism (CD) spectra. These data were brought in relationship to the transfection activity of these peptides in order to better understand the mechanism of peptide-mediated gene transfer. A DNA binding oligolysine (K16) and a peptide comprising K16 with an added peptide loop containing the arbitrary sequence RAD not known as a receptor ligand were used. Whereas the K16-DNA complex at 88% charge neutralization of the DNA phosphates collapsed into small toroidal particles with a diameter of 200 nm by dynamic light scattering, K16-cRAD did not. Instead, large aggregates were observed. CD spectra showed that the K16-DNA complexes were in a -ψ state observed at liquid crystalline phases. Increasing positive charge by addition of further K16 or disturbing the -ψ state by introducing the RAD-peptide loop resulted in increasing instability indicated by aggregation and loss of the -ψ CD spectrum of the complexes. Transfection experiments indicated that the aggregated material was the transfection-active component.
|Number of pages||8|
|Journal||Biochimica et Biophysica Acta - Gene Structure and Expression|
|Publication status||Published - 7 Jun 2002|
- Atomic force microscopy
- Circular dichroism spectroscopy
- Dynamic light scattering
- Peptide-DNA complex