Sequence/structure relationships in aromatic dipeptide hydrogels formed under thermodynamic control by enzyme-assisted self-assembly

Hughes, Meghan and Frederix, Pim W. J. M. and Raeburn, Jaclyn and Birchall, Louise S. and Sadownik, Jan and Coomer, Fiona C. and Lin, I-Hsin and Cussen, Edmund J. and Hunt, Neil T. and Tuttle, Tell and Webb, Simon J. and Adams, Dave J. and Ulijn, Rein V. (2012) Sequence/structure relationships in aromatic dipeptide hydrogels formed under thermodynamic control by enzyme-assisted self-assembly. Soft Matter, 8 (20). pp. 5595-5602. ISSN 1744-683X

Abstract

Self-assembled supramolecular structures of peptide derivatives often reflect a kinetically trapped state rather than the thermodynamically most favoured structure, which presents a challenge when trying to elucidate the molecular design rules for these systems. In this article we use thermodynamically controlled self-assembly, driven by enzymatic condensation of amino acid derivatives, to elucidate chemical composition/nanostructure relationships for four closely related Fmoc-dipeptide-methyl esters which form hydrogels; SF, SL, TF and TL. We demonstrate that each of the four systems self-assemble to form extended arrays of beta-sheets which interlock via pi-stacking of Fmoc-moieties, yet with subtle differences in molecular organisation as supported by rheology, fluorescence emission spectroscopy, infrared spectroscopy, X-ray diffraction analysis and molecular mechanics minimisation.

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