3 research outputs found
Reversible Native Chemical Ligation: A Facile Access to Dynamic Covalent Peptides
The
broad interest of using reversible covalent bonds in chemistry,
in particular at its interfaces with biology and materials science,
has been recently established through numerous examples in the literature.
However, the challenging exchange of peptide fragments using a dynamic
covalent
peptide bond has not yet been achieved without enzymatic catalysis
because of its high thermodynamic stability. Here we show that peptide
fragments can be exchanged by a chemoselective and reversible native
chemical ligation (NCL) which can take place at <i>N</i>-(methyl)-cysteine residues. This very mild reaction is efficient
in aqueous solution, is buffered at physiological pH in the presence
of dithiothreitol (DTT), and shows typical half-times of equilibration
in the 10 h range
Precision Templating with DNA of a Virus-like Particle with Peptide Nanostructures
We report here the preparation of
filamentous virus-like particles
by the encapsulation of a linear or circular double-stranded DNA template
with preassembled mushroom-shaped nanostructures having a positively
charged domain. These nanostructures mimic the capsid proteins of
natural filamentous viruses and are formed by self-assembly of coiled-coil
peptides conjugated at opposite termini with cationic segments and
poly(ethylene glycol) (PEG) chains. We found that a high molecular
weight of PEG segments was critical for the formation of monodisperse
and uniformly shaped filamentous complexes. It is proposed that electrostatic
attachment of the nanostructures with sufficiently long PEG segments
generates steric forces that increase the rigidity of the neutralized
DNA template. This stiffening counterbalances the natural tendency
of the DNA template to condense into toroids or buckle multiple times.
The control achieved over both shape and dimensions of the particles
offers a strategy to create one-dimensional supramolecular nanostructures
of defined length containing nucleic acids
Coassembled Cytotoxic and Pegylated Peptide Amphiphiles Form Filamentous Nanostructures with Potent Antitumor Activity in Models of Breast Cancer
Self-assembled peptide amphiphiles (PAs) consisting of hydrophobic, hydvrogen-bonding, and charged hydrophilic domains form cylindrical nanofibers in physiological conditions and allow for the presentation of a high density of bioactive epitopes on the nanofiber surface. We report here on the use of PAs to form multifunctional nanostructures with tumoricidal activity. The combination of a cationic, membrane-lytic PA coassembled with a serum-protective, pegylated PA was shown to self-assemble into nanofibers. Addition of the pegylated PA to the nanostructure substantially limited degradation of the cytolytic PA by the protease trypsin, with an 8-fold increase in the amount of intact PA observed after digestion. At the same time, addition of up to 50% pegylated PA to the nanofibers did not decrease the <i>in vitro</i> cytotoxicity of the cytolytic PA. Using a fluorescent tag covalently attached to PA nanofibers we were able to track the biodistribution in plasma and tissues of tumor-bearing mice over time after intraperitoneal administration of the nanoscale filaments. Using an orthotopic mouse xenograft model of breast cancer, systemic administration of the cytotoxic pegylated nanostructures significantly reduced tumor cell proliferation and overall tumor growth, demonstrating the potential of multifunctional PA nanostructures as versatile cancer therapeutics