4 research outputs found
Design and Construction of Supramolecular Nanobeacons for Enzyme Detection
Molecular beacons are typically water-soluble molecules that can convert specific chemical reactions or binding events into measurable optical signals, providing a noninvasive means to help understand cellular and subcellular activities at the molecular level. However, the soluble form of the current molecular beacon design often leads to their poor stability and facile degradation by nonspecific enzymes, and as a result, this undesired activation could give rise to false signals and thus poses a limitation for accurate detection of enzymatic activities. Here we report a proof-of-concept design and synthesis of a new type of supramolecular nanobeacon that is resistant to nonspecific enzymatic degradation in the self-assembled state but can be effectively cleaved by the target enzyme in the monomeric form. Our results show that the nanobeacon with a GFLG peptide linker could serve as an indicator for the presence of a lysosomal enzyme, cathepsin B
Enhanced Cellular Entry and Efficacy of Tat Conjugates by Rational Design of the Auxiliary Segment
Conjugation with a cell penetrating
peptide such as Tat presents
an effective approach to improve the intracellular accumulation of
molecules with low membrane permeability. This strategy, however,
leads to a reduced cellular entry of molecules that can cross cell
membrane effectively. We report here that covalent linkage of an additional
hydrophobic unit that mimics a hydrophobic domain near the Tat sequence
can further improve the cellular uptake of the parental conjugate
into cancer cells regardless of the membrane permeability of the unconjugated
molecule. Both fluorescent imaging and flow cytometry measurements
confirmed the effect of palmitoylation on the increased internalization
of the Tat conjugates with either 5-carboxyfluorescein (5-FAM), a
nonmembrane penetrating dye, or doxorubicin, an anticancer cancer
drug that can readily diffuse across cell membranes. In the case of
the Tat–doxorubicin conjugate, palmitoylation improves the
conjugate’s anticancer activity in both drug sensitive and
resistant cervical cancer cell lines. We further demonstrate that
modification of a Tat–5-FAM conjugate with a hydrophobic quencher
could not only efficiently quench the fluorescence outside of cancer
cell but also facilitate its entry into MCF-7 breast cancer cells.
These results highlight the importance of rational molecular design
of using peptide conjugation chemistry in cancer therapeutics and
diagnostics
Cellular Uptake and Cytotoxicity of Drug–Peptide Conjugates Regulated by Conjugation Site
Conjugation of anticancer drugs to
hydrophilic peptides such as
Tat is a widely adopted strategy to improve the drug’s solubility,
cellular uptake, and potency against cancerous cells. Here we report
that attachment of an anticancer drug doxorubicin to the <i>N</i>- or <i>C</i>-terminal of the Tat peptide can have a significant
impact on their cellular uptake and cytotoxicity against both drug-sensitive
and drug-resistant cancer cells. We observed higher cellular uptake
by both cell lines for <i>C</i>-terminal conjugate relative
to the <i>N</i>-terminal analogue. Our results reveal that
the <i>C</i>-terminal conjugate partially overcame the multidrug
resistance of cervical cancer cells, while the <i>N</i>-terminal
conjugate showed no significant improvement in cytotoxicity when compared
with free doxorubicin. We also found that both <i>N</i>-
and <i>C</i>-conjugates offer a mechanism to circumvent
drug efflux associated with multidrug resistance
Amino Acid Sequence in Constitutionally Isomeric Tetrapeptide Amphiphiles Dictates Architecture of One-Dimensional Nanostructures
The switching of
two adjacent amino acids can lead to differences
in how proteins fold thus affecting their function. This effect has
not been extensively explored in synthetic peptides in the context
of supramolecular self-assembly. Toward this end, we report here the
use of isomeric peptide amphiphiles as molecular building blocks to
create one-dimensional (1D) nanostructures. We show that four peptide
amphiphile isomers, with identical composition but a different sequence
of their four amino acids, can form drastically different types of
1D nanostructures under the same conditions. We found that molecules
with a peptide sequence of alternating hydrophobic and hydrophilic
amino acids such as VEVE and EVEV self-assemble into flat nanostructures
that can be either helical or twisted. On the other hand, nonalternating
isomers such as VVEE and EEVV result in the formation of cylindrical
nanofibers. Furthermore, we also found that when the glutamic acid
is adjacent to the alkyl tail the supramolecular assemblies appear
to be internally flexible compared to those with valine as the first
amino acid. These results clearly demonstrate the significance of
peptide side chain interactions in determining the architectures of
supramolecular assemblies