1. Directed self-assembly of dipeptides to form ultrathin hydrogel membranes
Eleanor K Johnson, Dave J Adams, Petra J Cameron J Am Chem Soc. 2010 Apr 14;132(14):5130-6. doi: 10.1021/ja909579p.
The dipeptide amphiphile Fmoc-Leu-Gly-OH has been induced to self-assemble into thin surface-supported hydrogel gel films and gap-spanning hydrogel membranes. The thickness can be closely controlled, giving films/membranes from tens of nanometers to millimeters thick. SEM and TEM have confirmed that the dipeptides self-assemble to form fibers, with the membranes resembling a dense "mat" of entangled fibers. The films and membranes were stable once formed. The films could be reversibly dried and collapsed, then reswollen to regain the gel structure.
2. Synergistic stiffening in double-fiber networks
Wolf H Rombouts, Marcel Giesbers, Jan van Lent, Frits A de Wolf, Jasper van der Gucht Biomacromolecules. 2014 Apr 14;15(4):1233-9. doi: 10.1021/bm401810w. Epub 2014 Mar 17.
Many biological materials are composite structures, interpenetrating networks of different types of fibers. The composite nature of such networks leads to superior mechanical properties, but the origin of this mechanical synergism is still poorly understood. Here we study soft composite networks, made by mixing two self-assembling fiber-forming components. We find that the elastic moduli of the composite networks significantly exceed the sum of the moduli of the two individual networks. This mechanical enhancement is in agreement with recent simulations, where it was attributed to a suppression of non-affine deformation modes in the most rigid fiber network due to the reaction forces in the softer network. The increase in affinity also causes a loss of strain hardening and an increase in the critical stress and stain at which the network fails.
3. Self-assembly and gelation properties of glycine/leucine Fmoc-dipeptides
Claire Tang, Rein V Ulijn, Alberto Saiani Eur Phys J E Soft Matter. 2013 Oct;36(10):111. doi: 10.1140/epje/i2013-13111-3. Epub 2013 Oct 3.
Self-assembly of aromatic peptide amphiphiles is known to be driven by a combination of π-π stacking of the aromatic moieties and hydrogen bonding between the peptide backbones, with possible stabilisation from the amino acid side chains. Phenylalanine-based Fmoc-dipeptides have previously been reported for their characteristic apparent pKa transitions, which were shown to coincide with significant structural and morphological changes that were peptide sequence dependent. Here, phenylalanine was replaced by leucine and the effect on the self-assembling behaviour of Fmoc-dipeptides was measured using potentiometry, fluorescence and infrared spectroscopy, transmission electron microscopy, X-ray scattering and shear rheometry. This study provides additional cues towards the elucidation of the sequence-structure relationship in self-assembling aromatic peptide amphiphiles.
