Effect of the spacer on the structure and self-assembly of FF peptide mimetics

We have designed and synthesized a series of FF peptide mimetics with conformationally rigid and flexible spacers to study the effect of spacers on their structure and self-assembly. The results help in understanding biomolecular aggregation and provide a strategy to obtain fractal pattern materials. From X-ray single crystal analysis, the m-diaminobenzene appended FF peptide mimetic adopts a duplex structure stabilized by multiple intermolecular hydrogen bonds. There is also a water molecule bridging between two strands of the duplex. Moreover, the duplex is stabilized by three face-to-face, face-to-edge and edge-to-edge π-π interactions. The duplex formation is also supported by mass spectrometry. In higher order packing, the dimeric subunits further self-assembled to form a complex sheet-like structure stabilized by multiple intermolecular hydrogen bonding and π-π stacking interactions. Moreover, the 1,4-butadiene and m-xylylenediamine appended FF peptide mimetics form stimuli-responsive organogels in a wide range of solvents including methanol. The rheology data of FF peptide mimetic gels as a function of angular frequency and oscillatory strain also supported the formation of strong physically crosslinked gels. The FE-SEM images of the xerogels obtained from different organic solvents show that the network morphology of FF peptide mimetics varies depending on the nature of the solvents.