| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Biomaterial Interfaces | Tuesday Sessions |
| Session BI-TuM |
| Session: | Biomaterial & Wet Interface Characterization |
| Presenter: | Johannes Franz, Max Planck Institute for Polymer Research |
| Authors: | J. Franz, Max Planck Institute for Polymer Research D. Schach, Max Planck Institute for Polymer Research J.E. Baio, Oregon State University D.J. Graham, University of Washington, USA D.G. Castner, University of Washington, USA M. Bonn, Max Planck Institute for Polymer Research T. Weidner, Max Planck Institute for Polymer Research, Germany |
| Correspondent: | Click to Email |
The cell membrane is the most important biological surface as its interaction with peptides is an integral part of transport, communication, energy transduction and survivability. However, an intrinsic difficulty in monitoring peptide interaction with membranes is the required surface sensitivity. Sum frequency generation (SFG) vibrational spectroscopy is well suited to study protein monolayers at lipid surfaces[1] because of its inherent surface specificity and is used to investigate molecular interactions of peptides with model membranes. In this study, three different peptides are shown to interact with model membranes in very different ways.
The internalization mechanism of the negatively charged cell-penetrating peptide SAP(E) is proposed as an aggregation on the cell surface followed by an endocytic uptake. Our data suggest peptide affinity is strongly dependent on the lipid headgroup charge with phosphocholine having the strongest interaction with SAP(E). Moreover, the interaction is limited to the headgroup region with no further insertion observable proving the first step of the proposed uptake mechanism. These findings were supported with complementary surface-sensitive UHV-techniques, i.e. X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS).
In contrast, viral fusion proteins can disrupt membranes and escape from endosomes when triggered at low pH. We are interested in the interaction of GALA, a peptide mimicking viral fusion proteins. While the peptide is unfolded and inactive around neutral pH, the sequence folds into its active α‑helical state at lower pH and causes membrane leakage. We follow GALA activity at the molecular level and probe peptide folding as well as the disturbance and hydration of individual leaflets within model bilayers.
Besides binding to and shredding bilayers, peptides can also help stabilize lipid membranes. For example, bovine serum albumin and specific antifreeze proteins can maintain cell membrane integrity at low temperatures. We briefly discuss preliminary results about the effects of protein-lipid interactions on the temperature stability of lipid mono- and bilayers.
[1] Chen, X., Chen, Z., BBA 1758 (2006), 1257-1273.