The surfactant-like peptide (Ala)(6)(Arg) is found to self-assemble into 3 nm-thick sheets in aqueous solution. Scanning transmission electron microscopy measurements of mass per unit area indicate a layer structure based on antiparallel dimers. At higher concentration the sheets wrap into unprecedented ultrathin helical ribbon and nanotube architectures.
A new synthetic tripeptide-based hydrogel has been discovered at physiological pH and temperature. This hydrogel has been thoroughly characterized using different techniques including field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, small- and wide-angle X-ray diffraction analyses, FT-IR, circular dichroism, and rheometric analyses. Moreover, this gel exhibits thixotropy and injectability. This hydrogel has been used for entrapment and sustained release of an antibiotic vancomycin and vitamin B12 at physiological pH and temperature for about 2 days. Interestingly, MTT assay of these gelator molecules shows almost 100% cell viability of this peptide gelator, indicating its noncytotoxicity.
Synthetic tripeptide based noncytotoxic hydrogelators have been discovered for releasing an anticancer drug at physiological pH and temparature. Interestingly, gel stiffness, drug release capacity and proteolytic stability of these hydrogels have been successfully modulated by incorporating d-amino acid residues, indicating their potential use for drug delivery in the future.
The self-assembled structure of toll-like receptor agonist lipopeptides containing the CSK4 peptide sequence is examined in aqueous solution. A remarkable dependence of morphology on the number of attached hexadecyl lipid chains is demonstrated, with spherical micelle structures for mono- and di-lipidated structures observed, but flexible wormlike micelles for the homologue containing three lipid chains. The distinct modes of assembly may have an important influence on the bioactivity of this class of lipopeptide.
We investigate the properties of
an antimicrobial surfactant-like
peptide (Ala)6(Arg), A6R, containing a cationic
headgroup. The interaction of this peptide with zwitterionic (DPPC)
lipid vesicles is investigated using a range of microscopic, X-ray
scattering, spectroscopic, and calorimetric methods. The β-sheet
structure adopted by A6R is disrupted in the presence of
DPPC. A strong effect on the small-angle X-ray scattering profile
is observed: the Bragg peaks from the DPPC bilayers in the vesicle
walls are eliminated in the presence of A6R and only bilayer
form factor peaks are observed. All of these observations point to
the interaction of A6R with DPPC bilayers. These studies
provide insight into interactions between a model cationic peptide
and vesicles, relevant to understanding the action of antimicrobial
peptides on lipid membranes. Notably, peptide A6R exhibits
antimicrobial activity without membrane lysis.
Transitions in nanostructure driven by pH are observed for a selfassembling peptide amphiphile (PA) with a cationic pentapeptide headgroup. At pH 3, the PA forms flat tape-like structures, while at pH 4 the PA assembles into twisted right handed structures. These twisted structures transform again to flat tape-like structures at pH 7. In complete contrast, spherical micelles are observed at pH 2. These changes in response to pH may be relevant to biological and pharmaceutical applications of this PA in skincare.
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