Control over Multiple Nano‐ and Secondary Structures in Peptide Self‐Assembly

Herein, we report the rich morphological and conformational versatility of a biologically active peptide (PEP‐1), which follows diverse self‐assembly pathways to form up to six distinct nanostructures and up to four different secondary structures through subtle modulation in pH, concentration and temperature. PEP‐1 forms twisted β‐sheet secondary structures and nanofibers at pH 7.4, which transform into fractal‐like structures with strong β‐sheet conformations at pH 13.0 or short disorganized elliptical aggregates at pH 5.5. Upon dilution at pH 7.4, the nanofibers with twisted β‐sheet secondary structural elements convert into nanoparticles with random coil conformations. Interestingly, these two self‐assembled states at pH 7.4 and room temperature are kinetically controlled and undergo a further transformation into thermodynamically stable states upon thermal annealing: whereas the twisted β‐sheet structures and corresponding nanofibers transform into 2D sheets with well‐defined β‐sheet domains, the nanoparticles with random coil structures convert into short nanorods with α‐helix conformations. Notably, PEP‐1 also showed high biocompatibility, low hemolytic activity and marked antibacterial activity, rendering our system a promising candidate for multiple bio‐applications.