(245e) The Role of Alpha-Helix Formation In the Self-Assembly of Protein-Analogous Micelles

Alpha-helical structure in a peptide chain has been shown to affect the geometry of self-assembled systems containing these molecules. In a related phenomenon, incorporation of a polypeptide into a self-assembled system has been shown to affect the helix-coil transition relative to the free polypeptide. This work presents a quantitative model of the interaction between self-assembly and the helix-coil transition in micelles formed from hydrophobic hydrocarbon tails and water-soluble polypeptides. Such structures are termed protein-analogous micelles and can exist in spherical, cylindrical, or flat geometries as dictated by thermodynamic considerations.

This work shows that alpha-helix formation is stabilized by the micellization process while the amount of stabilization increases with the strength of attraction between hydrophobic tails. Helix formation drives the micelle to form structures with less curvature than would be expected if the polypeptide existed in a random-coil state. A transition in protein-analogous micelles is expected from spherical to cylindrical micelles as helical content of the polypeptide headgroup increases. This prediction is verified experimentally for a protein-analogous micelle in which helical content is controlled using pH. These results aid the design of protein-analogous micelles to produce a desired shape.