Self-assembly of model collagen peptide amphiphiles

We have used cryo-transmission electron microscopy (cryo-TEM), small-angle neutron scattering (SANS), differential scanning calorimetry (DSC), and circular dichroism (CD) for microstructural characterization of amphiphiles that have a model collagen peptide headgroup. Single-tail amphiphiles and double-tail amphiphiles with short tails such as C12 and C14 formed spheroidal micelles. Further increase in tail length of the double-tail amphiphiles led to the formation of disklike micelles that aggregated to form a strandlike structure. SANS curves for double-tail amphiphiles were obtained at different contrasts by using different fractions of D₂O in the D₂O/H₂O mixture. SANS data analysis using the sphere method confirmed the structures imaged by cryo-TEM and provided a detailed structural characterization. CD data showed that the peptide's capacity to organize into a triple helix by intertwining with two neighboring molecules can be affected by increasing the tail length. Double-tail amphiphiles with tails such as C18 and C20 that are crystalline at room temperature disrupt the association of the triple helix at room temperature. Increasing the temperature to melt the crystalline tails helps restore the triple-helical conformation in the headgroups.