Biophysical characterization of a β-peptide bundle:: Comparison to natural proteins

We recently described the high-resolution X-ray structure of a helical bundle composed of eight copies of the beta-peptide Zwit-1F. Like many proteins in Nature, the Zwit-1F octamer contains parallel and antiparallel helices, extensive inter-helical electrostatic interactions, and a solvent-excluded hydrophobic core. Here we explore the stability of the Zwit-1F octamer using circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AU), differential scanning calorimetry (DSC), and NMR. These studies demonstrate that the thermodynamic and kinetic properties of Zwit-1F closely resemble those of alpha-helical bundle proteins. Together these studies should provide a model for the design of beta-peptide proteins with biological functions.