An increased flux of potassium ions into the mitochondrial matrix through the ATP-sensitive potassium channel (mitoKATP) has been shown to provide protection against ischemia-reperfusion injury. Recently, it was proposed that the mitochondrial-targeted isoform of the renal outer medullary potassium channel (ROMK) protein creates a pore-forming subunit of mitoKATP in heart mitochondria. Our research focuses on the properties of mitoKATP from heart-derived H9c2 cells. For the first time, we detected single-channel activity and describe the pharmacology of mitoKATP in the H9c2 heart-derived cells. The patch-clamping of mitoplasts from wild type (WT) and cells overexpressing ROMK2 revealed the existence of a potassium channel that exhibits the same basic properties previously attributed to mitoKATP. ROMK2 overexpression resulted in a significant increase of mitoKATP activity. The conductance of both channels in symmetric 150/150 mM KCl was around 97 ± 2 pS in WT cells and 94 ± 3 pS in cells overexpressing ROMK2. The channels were inhibited by 5-hydroxydecanoic acid (a mitoKATP inhibitor) and by Tertiapin Q (an inhibitor of both the ROMK-type channels and mitoKATP). Additionally, mitoKATP from cells overexpressing ROMK2 were inhibited by ATP/Mg2+ and activated by diazoxide. We used an assay based on proteinase K to examine the topology of the channel in the inner mitochondrial membrane and found that both termini of the protein localized to the mitochondrial matrix. We conclude that the observed activity of the channel formed by the ROMK protein corresponds to the electrophysiological and pharmacological properties of mitoKATP.
We report for the
first time on in situ transduction of electrochemical
responses of ion-selective electrodes, operating under non-zero-current
conditions, to emission change signals. The proposed novel-type PVC-based
membrane comprises a dispersed redox and emission active ion-to-electron
transducer. The electrochemical trigger applied induces a redox process
of the transducer, inducing ion exchange between the membrane and
the solution, resulting also in change of its emission spectrum. It
is shown that electrochemical signals recorded for ion-selective electrodes
operating under voltammetric/coulometric conditions correlate with
emission intensity changes recorded in the same experiments. Moreover,
the proposed optical readout offers extended linear response range
compared to electrical signals recorded in voltammetric or coulometric
mode.
H2O2 is a versatile chemical and can be generated by the oxygen reduction reaction (ORR) in proton donor solution in molecular solvents or room temperature ionic liquids (IL). We investigated this reaction at interfaces formed by eleven hydrophobic ILs and acidic aqueous solution as a proton source with decamethylferrocene (DMFc) as an electron donor. H2O2 is generated in colorimetrically detectable amounts in biphasic systems formed by alkyl imidazolium hexafluorophosphate or tetraalkylammonium bis(trifluoromethylsulfonyl)imide ionic liquids. H2O2 fluxes were estimated close to liquid|liquid interface by scanning electrochemical microscopy (SECM). Contrary to the interfaces formed by hydrophobic electrolyte solution in a molecular solvent, H2O2 generation is followed by cation expulsion to the aqueous phase. Weak correlation between the H2O2 flux and the difference between DMFc/DMFc+ redox potential and 2 electron ORR standard potential indicates kinetic control of the reaction.
A new concept of
easy to make, potentially disposable potentiometric
sensors is presented. A thermoprocessable carbon black-loaded, electronically
conducting, polylactide polymer composite was used to prepare substrate
electrodes of user’s defined shape/arrangement applying a 3D
pen in a hot melt process. Covering of the carbon black-loaded polylactide
3D-drawn substrate electrode with a PVC-based ion-selective membrane
cocktail results in spontaneous formation of a zip-lock structure
with a large contact area. Thus, obtained ion-selective electrodes
offer sensors of excellent performance, including potential stability
expressed by SD of the mean value of potential recorded equal to ±1.0
mV (n = 6) within one day and ±1.5 mV (n = 6) between five days. The approach offers also high
device-to-device potential reproducibility: SD of mean value of E
0 equal to ±1.5 mV (n =
5).
This paper is dedicated to the occasion of 65 th birthday of Hubert H. Girault to recognize his contribution to electrochemistry of liquid j liquid interfaces and fruitful collaboration.
The applicability of emission readout of ion‐selective electrodes, containing fluorimetrically active polyoctylthiophene in the membrane, operating under chronopotentiometric mode was studied. The electrochemical and optical signals were collected in the same experiment and compared. In both modes a change in recorded signal: potential or emission in time was observed while a constant current was applied to the sensor. The recorded signals (chronopotentiometric, fluoro‐chronopotentiometric curves and calculated transition times) were dependent on the concentration of potassium ions. The transition times calculated from electrochemical signals were linearly dependent on the concentration of potassium ions in solution within the range: 0.1–0.7 mM. Optically read transition times were also linearly dependent on concentration within the same range, however, they were shorter than those recorded electrochemically. This difference is attributed to various effects represented by the transition time: concentration increase of reduced form of the conducting polymer in the optical mode or depletion of potassium ions close to the membrane surface, in the electrochemical mode.
The applicability of model polydiacetylenes (PDAs) in hydrogen ions sensitive optodes was tested. Nanofibers mats were electrospun using a mixture of polyvinyl chloride (PVC) and polycaprolactone (PCL) together with 10, 12‐tricosadiynoic acid (TCDA) or 10,12‐pentacosadiynoic acid (PCDA). After the polymerization the mats were applied in colorimetric and fluorimetric pH sensors. The PDAs were formed by photopolymerization with a UV lamp (254 nm), resulting in a change of mats color from white to dark blue. The morphology of both fiber mats is similar (SEM images), and the average diameters of fibers were estimated as equal to 228±73 and 248±61 nm for TCDA and PCDA, respectively. As the pH increases, the color of the fiber mat changes from blue to red and the process can be followed visually. The result obtained by computer image analysis showed a sigmoidal increase in the intensity of red and a decrease in the intensity of blue color with increasing pH. A similar sigmoidal response is observed for the dependence of the emission intensity on the pH. Changes in the recorded signal occur in the pH range from 7 to 8.5 or from 8 to 9.5 for mats with TCDA and PCDA, respectively. Both readout modes can be successfully used for pH sensing with proposed nanofibrous mats in the range of pH close to the physiological pH range.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.