Insights into the Coassembly of Hydrogelators and Surfactants Based on Aromatic Peptide Amphiphiles

Abstract

The coassembly of small molecules is a useful means of increasing the complexity and functionality of their resultant supramolecular constructs in a modular fashion. In this study, we explore the assembly and coassembly of serine surfactants and tyrosine-leucine hydrogelators, capped at the N-termini with either fluorenyl-9-methoxycarbonyl (Fmoc) or pyrene. These systems all exhibit self-assembly behavior, which is influenced by aromatic stacking interactions, while the hydrogelators also exhibit β-sheet-type arrangements, which reinforce their supramolecular structures. We provide evidence for three distinct supramolecular coassembly models; cooperative, disruptive, and orthogonal. The coassembly mode adopted depends on whether the individual constituents (I) are sufficiently different, such that effective segregation and orthogonal assembly occurs; (II) adhere to a communal mode of self-assembly; or (III) act to compromise the assembly of one another via incorporation and disruption. We find that a greater scope for controllable coassembly exists within orthogonal systems; which show minimal relative changes in the native gelator's supramolecular structure by Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and fluorescence spectroscopy. This is indicative of the segregation of orthogonal coassembly constituents into distinct domains, where surfactant chemical functionality is presented at the surface of the gelator's supramolecular fibers. Overall, this work provides new insights into the design of modular coassembly systems, which have the potential to augment the chemical and physical properties of existing gelator systems.

Tunable Supramolecular Gel Properties by Varying Thermal History

“…Previously,b yu sing sub-gelation concentrations, we have observed that Fmoc-YL demonstrates ap ositive CD peak at approximately 305 nm, in addition to strong shorter wavelengths ignals centered around2 75 nm which may include a contribution from the tyrosine residues. [9] Upon increasing pregelation temperatures, positive peaks in the 275 and 305 nm regions invert to an egative signal ( Figure 3c), with the inversion point coinciding with the lowest relative mobility of fluorenyl and tyrosine residues observed by NMR spectroscopy (333-343K). Additionally,C Ds pectra of pre-gelation solutions at elevated temperatures ( Figure S4,S upporting Information) show that Fmoc-YLs olutions have an egative CD signal at relatively low temperatures (313-333 K) with intensity reduced at elevated temperatures (343 and 353 K).…”

Tunable Supramolecular Hydrogels for Selection of Lineage-Guiding Metabolites in Stem Cell Cultures

“…proteins or peptide motifs) [28][29][30] In order to tailor suitable materials, we made use of a two-component co-assembly approach comprising a peptide based gelator (the structural element) and a surfactant-like molecule that presents carboxylate functionality to the surface of fibres 31 , enabling subsequent cross-linking upon exposure to divalent cations (Ca 2+ ) present in tissue culture media. Specifically, when fluorenyl-9-methoxycarbonyldiphenylalanine, Fmoc-F2 24,32,33 was co-assembled with surfactant-like Fmoc-serine (Fmoc-S), the polar serine side chains were presented at the surface of the fibres (Fig 1a).…”

On the Role of Chirality in Guiding the Self‐Assembly of Peptides

“…Noncovalent interactions are collectively strong enough to form highly organized self‐assembled 3D supramolecular structures with a dynamic error correction property . However, controlling the self‐assembly of a multicomponent system in one pot is rather challenging . In contrast, the Adams group reported the self‐sorting behavior of two molecules by regulating the solution pH .…”