The effects of stacking interactions on the oxidation potentials of single strand oligonucleotides containing up to four consecutive adenines, alternated with thymines and cytosines in different sequences and ratios, have been determined by means of differential pulse voltammetry. Voltammetric measurements point toward the establishment in solution of structured oligonucleotide conformations, in which the nucleobases are well stacked altogether. Molecular dynamics simulations confirm that finding, indicating that single strands assume geometrical parameters characteristic of the B-DNA form. The analysis of the voltammetric signals in terms of a simple effective tight binding quantum model leads one to infer a robust set of parameters for treating hole transfer in one-electron-oxidized DNA containing adenines and thymines.
Spiky/hollow metal
nanoparticles have applications across a broad
range of fields. However, the current bottom-up methods for producing
spiky/hollow metal nanoparticles rely heavily on the use of strongly
adsorbing surfactant molecules, which is undesirable because these
passivate the product particles’ surfaces. Here we report a
high-yield surfactant-free synthesis of spiky hollow Au–Ag
nanostars (SHAANs). Each SHAAN is composed of >50 spikes attached
to a hollow ca. 150 nm diameter cubic core, which makes SHAANs highly
plasmonically and catalytically active. Moreover, the surfaces of
SHAANs are chemically exposed, which gives them significantly enhanced
functionality compared with their surfactant-capped counterparts,
as demonstrated in surface-enhanced Raman spectroscopy (SERS) and
catalysis. The chemical accessibility of the pristine SHAANs also
allows the use of hydroxyethyl cellulose as a weakly bound stabilizing
agent. This produces colloidal SHAANs that remain stable for >1
month
while retaining the functionalities of the pristine particles and
allows even single-particle SERS to be realized.
The UV-vis and the IR spectra of derivativized adenosine in dichloromethane have been recorded during potentiostatic oxidation at an optically transparent thin layer electrode. Oxidized adenosine shows a broad Zundel like absorption extending from 2800 up to 3600 cm(-1), indicating that a proton transfer process is occurring. Theoretical computations predict that proton transfer is indeed favored in oxidized 1:1 self-association complexes and allow to assign all the observed transient spectroscopic signals.
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