60 research outputs found
Cyclopentane-Peptide Nucleic Acids for Qualitative, Quantitative, and Repetitive Detection of Nucleic Acids
We report the development of chemically modified peptide
nucleic
acids (PNAs) as probes for qualitative and quantitative detection
of DNA. The remarkable stability of PNAs toward enzymatic degradation
makes this class of molecules ideal to develop as part of a diagnostic
device that can be used outside of a laboratory setting. Using an
enzyme-linked reporter assay, we demonstrate that excellent levels
of detection and accuracy for anthrax DNA can be achieved using PNA
probes with suitable chemical components designed into the probe.
In addition, we report on DNA-templated cross-linking of PNA probes
as a way to preserve genetic information for repetitive and subsequent
analysis. This report is the first detailed examination of the qualitative
and quantitative properties of chemically modified PNA for nucleic
acid detection and provides a platform for studying and optimizing
PNA probes prior to incorporation into new technological platforms
Influence of Hydrophobic Face Amino Acids on the Hydrogelation of β‑Hairpin Peptide Amphiphiles
Hydrophobic residues provide much
of the thermodynamic driving
force for the folding, self-assembly, and consequent hydrogelation
of amphiphilic β-hairpin peptides. We investigate how the identity
of hydrophobic side chains displayed from the hydrophobic face of
these amphiphilic peptides influences their behavior to expound on
the design criteria important to gel formation. Six peptides were
designed that globally incorporate valine, aminobutyric acid, norvaline,
norleucine, phenylalanine, or isoleucine on the hydrophobic face of
the hairpin to study how systematic changes in hydrophobic content,
β-sheet propensity, and aromaticity affect gelation. Circular
dichroism (CD) spectroscopy indicates that hydrophobic content, rather
than β-sheet propensity, dictates the temperature- and pH-dependent
folding and assembly behavior of these peptides. Transmission electron
microscopy (TEM) and small-angle neutron scattering (SANS) show that
the local morphology of the fibrils formed via self-assembly is little
affected by amino acid type. However, residue type does influence
the propensity of peptide fibrils to undergo higher order assembly
events. Oscillatory rheology shows that the mechanical rigidity of
the peptide gels is highly influenced by residue type, but there is
no apparent correlation between rigidity and residue hydrophobicity
nor β-sheet propensity. Lastly, the large planar aromatic side
chain of phenylalanine supports hairpin folding and assembly, affording
a gel characterized by a rate of formation and storage modulus similar
to the parent valine-containing peptide
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