No abstract

The dimers of terminal alkynes were synthesized through a room temperature reaction which used (diacetoxyiodo)benzene as oxidizing agent and acetonitrile as solvent. The structures were characterized by 1H NMR, 13C NMR. The electrochemical and spectrochemical properties of the compounds were also characterized by cyclic voltammetry and UV spectroscopy. Meanwhile, the single crystal X‐ray analysis of the model compound was discussed.Introduction of the thioaryl group in ortho position lead to the red shift of the UV absorption peaks, and the introduction of a large steric hindrance group reduced the influences of the intermolecular π‐π interactions on their electronic properties. Moreover the sulfur atom can form the stable S−Au bond with gold. These data indicated that compounds 3 b‐3 dare expected to be applied in the field of molecular wires.

Recently, a Na+-binding aptamer was reported to be embedded in a few RNA-cleaving DNAzymes, including NaA43, Ce13d, and NaH1. The Na+ aptamer consists of multiple GG stretches, which is a prerequisite for the formation of G-quadruplex (G4) structures. These DNAzymes require Na+ for activity but show no activity in the presence of K+ or other metal ions. Given that DNA can selectively bind K+ by forming a G4 structure, this work aims to answer whether this Na+ aptamer also uses a G4 to bind Na+. Through comparative ThT fluorescence spectrometry studies, while a control G4 DNA exhibited notable fluorescence enhancement up to 5 mM K+ with a Kd of 0.28 ± 0.06 mM, the Ce13d DNAzyme fluorescence was negligibly perturbed with similar concentrations of K+. Opposed to this, Ce13d displayed specific remarkable fluorescence decrease with low millimolar concentrations of Na+. NMR experiments at two different pH values suggest that Ce13d adopts a significantly different conformation or equilibrium of conformations in the presence of Na+ versus K+ and has a more stable structure in the presence of Na+. Additionally, absence of characteristic G4 peaks in one-dimensional 1H NMR suggest that G4 is not responsible for the Na+ binding. This hypothesis is confirmed by the absence of characteristic peaks in the CD spectra of this sequence. Therefore, we concluded that the aptamer must be selective for Na+ and that it binds Na+ using a structural element that does not contain G4.