Morphology, energetics and growth kinetics of diphenylalanine fibres

Diphenylalanine (FF) has been shown to self-assemble from water into heterogeneous fibres that are among the stiffest biomaterials known. How and why the fibres form has, however, not been clear. In this work, the nucleation and growth of FF fibres was investigated in a combined experimental and theoretical study. Scanning electron microscopy and optical microscopy showed FF fibre morphology to be hollow tubes of varying widths with occasional endcaps. Molecular dynamics simulations of FF nanostructures based on the bulk crystalline geometry demonstrated that axial growth stablilises the fibres and that structures with different widths show similar stabilities, in accord with the wide range of fibre widths observed experimentally. Linear dichroism (LD) spectroscopy was used to determine the thermal stability of the fibres, showing that FF solutions are fully monomeric at 70 degrees C and that fibres begin to form at similar to 40 degrees C upon cooling. The LD kinetic studies indicated a nucleation-driven assembly with subsequent fibre growth, but a secondary nucleation process is required to explain the data.

Automated summary

The study revealed that diphenylalanine (FF) can self-assemble into stiff fibers with hollow tube morphology of varying widths, which show similar stabilities despite different diameters. Thermal stability analysis using linear dichroism spectroscopy showed that FF solutions are monomeric at 70 degrees C and begin to form fibers around 40 degrees C. The kinetics studies suggest a nucleation-driven assembly process with subsequent fiber growth, requiring a secondary nucleation process to explain the data.