Cellular uptake and biophysical properties of galactose and/or tryptophan containing cell-penetrating peptides

Glycosylated cell penetrating peptides (CPPs) have been conjugated to a peptide cargo and the efficiency of cargo delivery into wild type Chinese hamster ovary (CHO) and proteoglycan deficient CHO cells has been quantified by MALDI-TOF mass spectrometry and compared to tryptophan- or alanine containing CPPs. In parallel, the behavior of these CPPs in contact with model membranes has been characterized by different biophysical techniques: Differential Scanning and Isothermal Titration Calorimetries, Imaging Ellipsometry and Attenuated Total Reflectance IR spectroscopy. With these CPPs we have demonstrated that tryptophan residues play a key role in the insertion of a CPP and its conjugate into the membrane: galactosyl residues hampered the internalization when introduced in the middle of the amphipathic secondary structure of a CPP but not when added to the N-terminus, as long as the tryptophan residues were still present in the sequence. The insertion of these CPPs into membrane models was enthalpy driven and was related to the number of tryptophans in the sequence of these secondary amphipathic CPPs. Additionally, we have observed a certain propensity of the investigated CPP analogs to aggregate in contact with the lipid surface. (C) 2011 Elsevier B.V. All rights reserved.