9 research outputs found
New Class of Heterogeneous Helical Peptidomimetics
A new
class of unnatural heterogeneous foldamers is reported to
contain alternative α-amino acid and sulfono-γ-AA amino
acid residues in a 1:1 repeat pattern. Two-dimensional NMR data show
that two 1:1 α/sulfono-γ-AA peptides with diverse side
chains form analogous right-handed helical structures in solution.
The effects of sequence length, side chain, N-capping, and temperature
on folding propensity were further investigated using circular dichroism
and small-angle X-ray scattering
Solid-Phase Synthesis of γ-AApeptides Using a Submonomeric Approach
The solid-phase synthesis of γ-AApeptides using a novel submonomeric approach that utilizes an allyl protection is reported. The strategy successfully circumvents the necessity of preparing γ-AApeptide building blocks in order to prepare γ-AApeptide sequences. This method will maximize the potential of developing chemically diverse γ-AApeptide libraries and thereby facilitate the biological applications of γ-AApeptides in the future
Helical Antimicrobial Sulfono-γ-AApeptides
Host-defense
peptides (HDPs) such as magainin 2 have emerged as
potential therapeutic agents combating antibiotic resistance. Inspired
by their structures and mechanism of action, herein we report the
first example of antimicrobial helical sulfono-γ-AApeptide foldamers.
The lead molecule displays broad-spectrum and potent antimicrobial
activity against multi-drug-resistant Gram-positive and Gram-negative
bacterial pathogens. Time-kill studies and fluorescence microscopy
suggest that sulfono-γ-AApeptides eradicate bacteria by taking
a mode of action analogous to that of HDPs. Clear structure–function
relationships exist in the studied sequences. Longer sequences, presumably
adopting more-defined helical structures, are more potent than shorter
ones. Interestingly, the sequence with less helical propensity in
solution could be more selective than the stronger helix-forming sequences.
Moreover, this class of antimicrobial agents are resistant to proteolytic
degradation. These results may lead to the development of a new class
of antimicrobial foldamers combating emerging antibiotic-resistant
pathogens
Cellular Translocation of a γ-AApeptide Mimetic of Tat Peptide
Cell-penetrating peptides including the trans-activating
transcriptional
activator (Tat) from HIV-1 have been used as carriers for intracellular
delivery of a myriad of cargoes including drugs, molecular probes,
DNAs and nanoparticles. Utilizing fluorescence flow cytometry and
confocal fluorescence microscopy, we demonstrate that a γ-AApeptide
mimetic of Tat (48–57) can cross the cell membranes and enter
the cytoplasm and nucleus of cells, with efficiency comparable to
or better than that of Tat peptide (48–57). Deletion of the
four side chains of the γ-AApeptide attenuates translocation
capability. We also establish that the γ-AApeptide is even less
toxic than the Tat peptide against mammalian cells. In addition to
their low toxicity, γ-AApeptides are resistant to protease degradation,
which may prove to be advantageous over α-peptides for further
development of molecular transporters for intracellular delivery
Cellular Translocation of a γ-AApeptide Mimetic of Tat Peptide
Cell-penetrating peptides including the trans-activating
transcriptional
activator (Tat) from HIV-1 have been used as carriers for intracellular
delivery of a myriad of cargoes including drugs, molecular probes,
DNAs and nanoparticles. Utilizing fluorescence flow cytometry and
confocal fluorescence microscopy, we demonstrate that a γ-AApeptide
mimetic of Tat (48–57) can cross the cell membranes and enter
the cytoplasm and nucleus of cells, with efficiency comparable to
or better than that of Tat peptide (48–57). Deletion of the
four side chains of the γ-AApeptide attenuates translocation
capability. We also establish that the γ-AApeptide is even less
toxic than the Tat peptide against mammalian cells. In addition to
their low toxicity, γ-AApeptides are resistant to protease degradation,
which may prove to be advantageous over α-peptides for further
development of molecular transporters for intracellular delivery
Lipidated Cyclic γ‑AApeptides Display Both Antimicrobial and Anti-inflammatory Activity
Antimicrobial peptides (AMPs) are
host-defense agents capable of
both bacterial membrane disruption and immunomodulation. However,
the development of natural AMPs as potential therapeutics is hampered
by their moderate activity and susceptibility to protease degradation.
Herein we report lipidated cyclic γ-AApeptides that have potent
antibacterial activity against clinically relevant Gram-positive and
Gram-negative bacteria, many of which are resistant to conventional
antibiotics. We show that lipidated cyclic γ-AApeptides mimic
the bactericidal mechanism of AMPs by disrupting bacterial membranes.
Interestingly, they also harness the immune response and inhibit lipopolysaccharide
(LPS) activated Toll-like receptor 4 (TLR4) signaling, suggesting
that lipidated cyclic γ-AApeptides have dual roles as novel
antimicrobial and anti-inflammatory agents
Detecting Active Deconjugating Enzymes with Genetically Encoded Activity-Based Ubiquitin and Ubiquitin-like Protein Probes
Post-translational modification of proteins by Ubiquitin
(Ub) and
Ubiquitin-like proteins (Ubls) can be reversed by deconjugating enzymes,
which have been implicated in different pathways and associated with
various human diseases. To understand the activity and dynamics of
deconjugating enzymes, multiple synthetic and semi-synthetic Ub/Ubl
probes have been developed, and some of them have been applied to
screen inhibitors of deconjugating enzymes. Since these Ub/Ubl probes
are generally not cell-permeable, different strategies have been developed
to deliver Ub/Ubl probes to live cells. However, till now, no Ub/Ubl
probes can be expressed in live cells to directly report on the activities
of deconjugating enzymes in the most relevant cellular environment.
Here, we genetically encoded cross-linkable Ub/Ubl probes in live E. coli and HEK293T cells. These probes can cross-link
with deconjugating enzymes in vitro and in
vivo. Using these Ub probes combined with mass spectrometry,
we have successfully identified endogenous deconjugating enzymes in
live cells. We believe that these genetically encoded Ub/Ubl probes
are valuable for investigating biological functions of deconjugating
enzymes in physiological environments
Lipo-γ-AApeptides as a New Class of Potent and Broad-Spectrum Antimicrobial Agents
There is increasing demand to develop antimicrobial peptides
(AMPs)
as next generation antibiotic agents, as they have the potential to
circumvent emerging drug resistance against conventional antibiotic
treatments. Non-natural antimicrobial peptidomimetics are an ideal
example of this, as they have significant potency and in vivo stability.
Here we report for the first time the design of lipidated γ-AApeptides
as antimicrobial agents. These lipo-γ-AApeptides show potent
broad-spectrum activities against fungi and a series of Gram-positive
and Gram-negative bacteria, including clinically relevant pathogens
that are resistant to most antibiotics. We have analyzed their structure–function
relationship and antimicrobial mechanisms using membrane depolarization
and fluorescent microscopy assays. Introduction of unsaturated lipid
chain significantly decreases hemolytic activity and thereby increases
the selectivity. Furthermore, a representative lipo-γ-AApeptide
did not induce drug resistance in <i>S. aureus</i>, even
after 17 rounds of passaging. These results suggest that the lipo-γ-AApeptides
have bactericidal mechanisms analogous to those of AMPs and have strong
potential as a new class of novel antibiotic therapeutics
Nanorods Formed from a New Class of Peptidomimetics
Although peptide amphiphiles have been explored as nanomaterials
for different applications, nanostructures formed by hierarchical
molecular assembly of sequence-specific peptidomimetics are much less
developed. Such protein-like nanomaterials could enhance the current
application of peptide-based amphiphiles by enriching the diversity
of nanostructures, increasing <i>in vivo</i> stability for
biomedical applications, and facilitating the understanding of biomacromolecular
self-assembly. Herein we present a biomimetic γ-AApeptide amphiphile
which forms nanorods. Our results demonstrate the capability of γ-AApeptide
amphiphiles as a potential scaffold for the preparation of biomimetic
and bioinspired nanostructures. The programmability and biocompatibility
of γ-AApeptides could lead to novel nanomaterials for a wide
variety of applications