Microfluidic Channel Flow Cell for Simultaneous Cryoelectrochemical Electron Spin Resonance

Crystal violet as an i-motif structure probe for reversible and label-free pH-driven electrochemical switch

A simple pH-induced electrochemical switch based on an i-motif structure is developed by using crystal violet as a selective electrochemical probe for the i-motif structure. Thiol-modified cytosine-rich single-strand oligonucleotide (C-rich ssDNA) can be self-assembled on the gold electrode surface via gold-sulfur interaction. Crystal violet is employed as an electrochemical probe for the i-motif structure because of its capability of binding with the i-motif structure through an end-stacking mode. In acidic aqueous solution, crystal violet may approach the electrode surface owing to the formation of the i-motif structure, resulting in an obvious signal, so-called "ON" state. Whereas in neutral or basic aqueous solution, the i-motif structure unfolds to dissociative single strand, which causes crystal violet to leave from the electrode surface, and a weak signal is obtained, so-called "OFF" state. In addition, in the range of pH 4.6-7.3, the increase in current has a good linear relationship (R=0.989) with pH value in the testing solutions. This pH-driven electrochemical switch has the advantages of simplicity, sensitivity, high selectivity, and good reversibility. Furthermore, it provides a possible platform for pH measurement.

The world as viewed by and with unpaired electrons

Recent advances in electron paramagnetic resonance (EPR) include capabilities for applications to areas as diverse as archeology, beer shelf life, biological structure, dosimetry, in vivo imaging, molecular magnets, and quantum computing. Enabling technologies include multifrequency continuous wave, pulsed, and rapid scan EPR. Interpretation is enhanced by increasingly powerful computational models.

Crystal violet as a G-quadruplex-selective probe for sensitive amperometric sensing of lead

A sensitive and selective amperometric sensing platform for lead (Pb(2+)) was developed based on a Pb(2+)-induced G-rich DNA conformational switch from a random-coil to G-quadruplex (G4) with crystal violet as the G4-binding indicator.

Reversed redox generation of silyl radicals in a four-electrode flow-through EPR spectroelectrochemical cell

A flow-through four-electrode EPR spectroelectrochemical cell was developed which allowed the observation of silyl radical formation in apparently multielectron electrochemical processes, in which these species could not be detected directly because of the high driving force of their further reduction/oxidation leading to non-paramagnetic products. Silyl radicals thus generated were characterized by spin trapping with alpha-phenyl-N-tert-butyl nitrone (PBN), intramolecular spin trapping or by direct detection. The overall multielectron process is realized in the first, generating, compartment of the cell and the ionic species formed are then transformed into the corresponding radicals in the second compartment via a one-electron redox process in the opposite direction, e.g. two-electron reductions of Ph(3)SiCl or Et(3)SiCl followed by one-electron oxidation of the resulting Ph(3)Si(-) or Et(3)Si(-) anions (+2e/-e process). These radical species were then identified as their secondary paramagnetic products or by their spin trapping with PBN. Using (2-[cyclohex-3-enyl]ethyl)dimethyl chlorosilane in this process, the formation of the silicon-centered radical and its intramolecular addition across the internal double bond were evidenced by spin trapping. The reduction of electrophilic silicon intermediates issued from the oxidation of Ph(3)SiSiPh(3) (-2e/+2e process) resulted in Ph(3)Si* radicals trapped with PBN. The reduction of the electrochemically prepared persistent dication of a stable disilene, thiatetrasilacyclopentene, allowed generation of a disilene cation radical characterized by EPR.