Probing the importance of lateral hydrophobic association in self-assembling peptide hydrogelators |
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Authors: | Karthikan Rajagopal Bulent Ozbas Darrin J Pochan Joel P Schneider |
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Institution: | (1) Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA;(2) Materials Science and Engineering Department, Delaware Biotechnology Institute, University of Delaware, Newark, DE 19716, USA |
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Abstract: | A class of peptides has been designed whose ability to self-assemble into hydrogel is dependent on their conformationally
folded state. Under unfolding conditions aqueous peptide solutions are freely flowing having the viscosity of water. When
folding is triggered by external stimuli, peptides adopt a β-hairpin conformation that self-assembles into a highly crosslinked
network of fibrils affording mechanically rigid hydrogels. MAX 1, a 20 residue, amphiphilic hairpin self-assembles via a mechanism
which entails both lateral and facial self-assembly events to form a network of fibrils whose local structure consists of
a bilayer of hairpins hydrogen bonded in the direction of fibril growth. Lateral self-assembly along the long axis of the
fibril is mainly facilitated by intermolecular hydrogen bonding between the strands of distinct hairpins and the formation
of hydrophobic contacts between residue side chains of laterally associating hairpins. Facial assembly is driven by the hydrophobic
collapse of the valine-rich faces of the amphiphilic hairpins affording a bilayer laminate. The importance of forming lateral
hydrophobic contacts during hairpin self-assembly and the relative contribution these interactions have towards nano-scale
morphology and material rigidity is probed via the study of: MAX1, a hairpin designed to exploit lateral hydrophobic interactions;
MAX 4, a peptide with reduced ability to form these interactions; and MAX5, a control peptide. CD spectroscopy and rheological
experiments suggest that the formation of lateral hydrophobic interactions aids the kinetics of assembly and contributes to
the mechanical rigidity of the hydrogel. Transmission electron microscopy (TEM) shows that these interactions play an essential
role in the self-assembly process leading to distinct nano-scale morphologies.
Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users. |
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Keywords: | Peptide Self-assembly Hydrogel Tissue engineering Design Viscoelastic |
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