2 research outputs found
Charge Transfer through Modified Peptide Nucleic Acids
We studied the charge transfer properties of bipyridine-modified
peptide nucleic acid (PNA) in the absence and presence of ZnÂ(II).
Characterization of the PNA in solution showed that ZnÂ(II) interacts
with the bipyridine ligands, but the stability of the duplexes was
not affected significantly by the binding of ZnÂ(II). The charge transfer
properties of these molecules were examined by electrochemistry for
self-assembled monolayers of ferrocene-terminated PNAs and by conductive
probe atomic force microscopy for cysteine-terminated PNAs. Both electrochemical
and single molecular studies showed that the bipyridine modification
and ZnÂ(II) binding do not affect significantly the charge transfer
of the PNA duplexes
Effect of Backbone Flexibility on Charge Transfer Rates in Peptide Nucleic Acid Duplexes
Charge transfer (CT) properties are compared between
peptide nucleic
acid structures with an aminoethylglycine backbone (aeg-PNA) and those
with a γ-methylated backbone (γ-PNA). The common aeg-PNA
is an achiral molecule with a flexible structure, whereas γ-PNA
is a chiral molecule with a significantly more rigid structure than
aeg-PNA. Electrochemical measurements show that the CT rate constant
through an aeg-PNA bridging unit is twice the CT rate constant through
a γ-PNA bridging unit. Theoretical calculations of PNA electronic
properties, which are based on a molecular dynamics structural ensemble,
reveal that the difference in the CT rate constant results from the
difference in the extent of backbone fluctuations of aeg- and γ-PNA.
In particular, fluctuations of the backbone affect the local electric
field that broadens the energy levels of the PNA nucleobases. The
greater flexibility of the aeg-PNA gives rise to more broadening,
and a more frequent appearance of high-CT rate conformations than
in γ-PNA