Ditryptophan Conjugation Triggers Conversion of Biotin Fibers into Soft Spherical Structures

Abstract

Trigger happy: Biotin and its methyl ester form long fibers in solution, which are transformed into soft spherical structures upon simple conjugation with ditryptophan dipeptide (see picture). Such morphogenesis is not achieved in a controlled fashion by other aromatic amino acids.

Modulating peptide amphiphile morphology by gold nanocolloids

“…Ga + ions were used to mill these soft structures and SEM micrographs revealed that these structures are hollow from inside ( Fig. 8) [40].…”

“…The sample was directly mounted on the stage under native conditions and images were taken with the help of focused-ion-beam/scanning electron microscope dual beam system (NOVA 600 NANOLAB, D97 FEI). The milling process of soft material depends upon three important things viz beam current, accelerating voltage and mill depth to minimize surface artifacts [40].…”

“…All peptide conjugates were synthesized by established lab protocol [37][38][39][40] using simple solution phase fragment condensation methodologies using Boc chemistry and in the presence of HOBt (ESI). Purity of final product was checked by analytical RP-HPLC (conditions for all purifications: 0.1% trifluoroacetic acid in water (eluent A) to 0.1% trifluoroacetic acid in acetonitrile (eluent B) (0-60% in 45 min), flow: 1 mL/min, column: Agilent's Eclipse XDB-C18, 4.6 Â 250 mm at RT).…”

“…Curiously, unlike self-assembling dipeptides made from aromatic amino acid such as phenylalanine, ditryptophan is unable to form ordered structures in solution [36]. However, introduction of suitable chemical modifications to augment non-covalent interactions, by employing flexible or rigid scaffolds or conjugation to other biomolecules, affords well-defined soft structures and notably, these soft structures are responsive toward external stimuli, such as presence of biologically active cations or brief exposure to sunlight [37][38][39][40][41].…”

Mannosylated self-assembled structures for molecular confinement and gene delivery applications

“…As a result of our investigations, we have discovered peptide-based supramolecular ensembles where some of them respond to colchicine, physiologically relevant cations, and covalently attached structure modifiers [12][13][14][15].…”