Cathodes switchable

Cheng and co-workers recently reported Fc-cyclopeptides 12-15 (Scheme 5.4) and showed that they acted as redox-switchable cation receptors [26]. These Fc-cyclopeptides exhibited strong anodic shifts of their electrode potentials in the presence of alkaline earth metals and lanthanides. The extent of the anodic shift can be correlated with the charge density of the metal ion with a bias toward binding of lanthanides, alkaline earth metals, and the least sensitivity to alkaline metals [26]. Chowdhury et al, reported the syntheis and interaction of cychc Fc-Histidine conjagates 16 with metal ions (Scheme 5.5). Electrochemical measurements showed that the compound exhibited cathodic shifts in the order Na Li K+>Cs which in the order of their ionic sizes and suggest that the observed shift relates to the cavity of the compound [27]. 

Miller, L. L., and Zhou, Q. X., Poly(A -methylpyrrolium) poly(styrenesulfonate). A conductive electrically switchable cation exchanger that cathodically binds and an-odically releases dopamine, Macromolecules, 20, 1594-1597 (1987). 

Fig. 10 (A) Polarization curves of the biofuel cell with the pH-switchable 02-cathode obtained at different pH values generated in situ by the enzyme logic network (a) pH ca. 6, (b) pH ca. 4, (c) pH ca. 6. Inset The reversible changes of the open-circuit voltage produced by the cell at the variable pH. (B) Electrical power density generated by the biofuel cell on different load resistances at different pH values generated in situ by the enzyme logic network (a) pH ca. 6, (b) pH ca. 4, (c) pH ca. 6. Inset The reversible changes of the maximum power density produced by the biofuel cell at the variable pH, (C) The maximum power density produced by the biofuel cell as the function of different combinations of the input signals. (Adapted from ref. 76 with permission).

Fig. 4.62. hQh-ICR hybrid instrumentation. This instrument is equipped with an ESI-to-MALDI switchable ion source that makes use of a two-stage ion funnel (d), ) to focus ions into a RF hexapole ion guide (h, ). The ions then pass a quadmpole ( ) that may either be mn as band pass (q) or as mass-selective device (Q) and then reach a multifunctional RF hexapole ion trap (h, ) where they can be i) accumulated, ii) coUisionally activated, or Hi) reacted with radical anions from the NCI source to effect ETD as required. For mass analysis the ions are then guided via an RF-oiily hexapole ( ) into the ICR cell ( ) where a hollow cathode ( ) is attached for BCD. Schematic of Bruker Solarix instrument series by courtesy of Bruker Daltonik, Bremen. 

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