Tubular to spherical mesoscopic self‐assembly of C‐ and N‐termini capped dileucines

Abstract

Among the plethora of aromatic and aliphatic dipeptide sequences that are successfully employed in nanoarchitecture and nanotechnology, dileucines (Leu‐Leu) is known for its self‐sorting behavior like diphenylalanine (Phe‐Phe), the most explored motif till date. However, only a few reports demonstrate the effects of capping groups on Leu‐Leu self‐assembly. Hence, to understand the effect of hydrophobic substituent on C‐/N‐termini, a series of Leu‐Leu derivatives are prepared and their self‐assembled morphology is evaluated. Spherical and tubular mesoscopic morphologies of C‐ and N‐termini capped Leu‐Leu owing to H‐bonding, π‐π stacking and van der Waals interactions are reported. Attachment of alkynes (propyne) at C‐termini results in micro‐tubes and rods for Boc‐Leu‐Leu‐Propyne and Fc‐Leu‐Leu‐Propyne, respectively. Hollow morphology was observed and substantiated by TEM and confocal microscopy. These micro‐tubes and micro‐rods transform into spherical nanoparticles after click conjugation at C‐termini which clearly show the effect of chemical modification on their self‐assembly. Therefore, subtle variations of capping groups result in remarkable changes of self‐assembled morphology, which suggests that the terminal capping is an important factor for rational design of short peptide‐based biomaterial.

Synthesis, characterization, and investigation of capacitance and redox properties of self-assembled Phe–Phe with ferrocene conjugates

“…It is also well known that ferrocene can enhance the electrochemical behavior by conjugating with peptides. 36–39 To investigate this, we performed cyclic voltammetry (CV) studies. The CV study on control ferrocene peptide Fc–Phe–Phe–propyne ( 4 ) in the absence of the conjugation of the nucleoside showed a clear reversible redox behavior (Fig.…”

“…Thus, ferrocene forms a nanorod self-assembled structure when conjugated with amino acids and it changes from nanorods to perfect spherical structures after an incubation time of one week in a 50% EtOH/water solution. 38…”

Effect of Stereochemistry and Hydrophobicity on the Self‐Assembly of Phe‐Phe‐Nucleoside Conjugates

“…It is known that the initially formed (kinetic control) nanospheres get closer and connect to each other to form thermodynamically stable rods upon incubation. [33,[39][40][41][42][43][44][45] The timedependent self-assembly of peptides 11-13 was followed using FESEM imaging. Even after 8 days, no further growth into rods Scheme 6.…”

“…It is known that the initially formed (kinetic control) nanospheres get closer and connect to each other to form thermodynamically stable rods upon incubation. [ 33,39–45 ] The time‐dependent self‐assembly of peptides 11–13 was followed using FESEM imaging. Even after 8 days, no further growth into rods or into any other structural features was observed, with structures remaining as spheres (Figure S21, Supporting Information).…”

Cyclic dipeptides: Biological activities and self‐assembled materials

“…Peptide strand length and subtle chemical modification of C-and N-termini both have a remarkable effect on self-assembled morphology. [72][73] For example, four cyclo(L-Lys-L-Glu) derivatives self-assembled into gels in different organic solvents. Introduction of carboxylic acid and Fmoc group enhanced the ability of gelation in PBS, which could be attributed to hydrogen bonds and π-stacking interactions provided by fluorenyl.…”