Amino acid–bile acid based molecules: extremely narrow surfactant nanotubes formed by a phenylalanine-substituted cholic acid

Abstract

An amino acid-substituted bile acid forms tubular aggregates with inner and outer diameters of about 3 and 6 nm. The diameters are unusually small for surfactant self-assembled tubes. The results enhance the spectrum of applications of supramolecular tubules and open up possibilities for investigating a novel class of biological amphiphiles.

Multi stimuli response of a single surfactant presenting a rich self-assembly behavior

“…37 Bile salt derivatives exhibit different self-assembly behaviours compared to their precursors. [38][39][40][41][42][43] They reveal efficient gelation properties 44,45 and present appealing stimuli dependent aggregation, especially in derivatives containing hydrophobic residues. 46,47 One such derivative, the naphthoilaminesubstituted cholic acid (HNaphC, Fig.…”

Twisted nanoribbons from a RGD-bearing cholic acid derivative

“…Molecules that arrange into tubules are often observed. In some cases, tubules can present stimuli-responsive features as well as tunable size or charge [35][36][37][38][39][40][41][42]. A plentitude of low molecular weight gelators formed by BA derivatives have been also investigated [30,[43][44][45][46].…”

A tryptophan-substituted cholic acid: Expanding the family of labelled biomolecules

“…For example, the functionalization of both the side chain and the tetracyclic system is observed to lead to efficient gelators in organic solvents as well as in aqueous solutions [22], and the possibility to enhance their efficiency by using catanionic mixtures of the derivatives was demonstrated [23], whereas the BAs functionalized in their rigid backbone, selfassemble into lamellae or tubules [24][25][26][27][28][29][30]. In particular, the selective substitution of one of the steroid hydroxyl groups by an adamantly group gives derivatives that self-organize in lamellar arrays [24], whereas the introduction of an aromatic residue gives compounds able to self-associate into tubular structures [26][27][28][29][30][31][32][33][34] showing sometimes unique features such as extremely narrow cross sections [27,28], thermo- [33,34] or pH-responsive aggregations [32] and catanionic controlled Page 3 of 25 A c c e p t e d M a n u s c r i p t 4 compositions [31]. Tubular structures are also formed by BA molecules substituted with monosaccharide residues through an unusual mechanism involving scrolls as intermediates [25], whereas vesicles are given by some Gemini derivatives [35].…”

“…1). The β-L-TrpC belongs to a new family of BA-based molecules bearing a hydrophobic amino acid residue on the steroid nucleus [27,28]. In particular, its synthesis and self-assembly characterization follow the one of a tryptophan-substituted deoxycholic acid recently reported [45], thus extending the family of Trp-substituted BA molecules.…”