A tetrodotoxin-sensitive persistent sodium current, IpNa, was found in guinea pig ventricular myocytes by whole-cell patch clamping. This current was characterized in cells derived from the basal ...left ventricular subendocardium, midmyocardium, and subepicardium. Midmyocardial cells show a statistically significant (P <0.05) smaller IpNa than subendocardial and subepicardial myocytes. There was no significant difference in IpNa current density between subepicardial and subendocardial cells. Computer modeling studies support a role of this current in the dispersion of action potential duration across the ventricular wall.
The two enantiomerically pure bridging ligands (±)-ctpy-x-ctpy have been prepared employing a two-fold stereospecific alkylation reaction of the enantiomerically pure, chiral terpyridyl-type ligands ...(±)-ctpy. The reaction of each of the enantiomerically pure bridging ligands with Fe2+ gives rise to chiral coordination polymers whose formation and stoichiometry were followed spectrophotometrically. An assignment of the absolute configuration of the formed helical polymeric structures was carried out on the basis of circular dichroism studies. Highly ordered domains (as determined from STM imaging) of the enantiomerically pure chiral redox polymers could be prepared via the interfacial reaction, over an HOPG substrate, of the bridging ligand in CH2Cl2 and FeSO4 in water. The degree of polymerization was estimated to be up to 60 from analysis of the STM images of the highly ordered domains on HOPG. The helicality of the domains was compared to the configuration obtained from the circular dichroism studies. The electrochemical properties of the polymers were investigated using cyclic voltammetry and the results compared to those of the respective monomeric complexes. The redox behavior of the iron centers in the polymer was comparable to that of the monomeric complex Fe((−)-ctpy)2(PF6)2 as well as to that of Fe(tpy)2(PF6)2. The polymeric materials undergo electrodeposition following the two-electron reduction of each bridging ligand unit (one electron per terpyridine group). No ligand-mediated metal−metal interactions were evident from the cyclic voltammetric measurements, suggesting that the metal centers act independently. Moreover, oxidation of the metal centers within the polymeric materials did not give rise to electrodeposition.
We report the synthesis and photophysical properties of two different photonic devices. The first system describes dinuclear metal complexes with a rigid and linear bridging ligand (PAP) that ...contains an adamantane spacer. We discuss the correlation between the nature of the bridging ligand and the electrochemical as well as photophysical properties of the metal complexes. Two interesting observations can already be pointed out: (i) the lifetime of the intermediate electron-transfer product Ru
III–PAP–Os
II is very long (130 μs); and (ii) for the first time in a dinuclear Ru/Os system, the rate constant of energy transfer from the Ru(II) to the Os(II) unit is faster than the rate of the electron transfer from the Ru(II) to the Os(III) unit. The second system represents a photonic switch which is built up by two subunits, a rhenium complex as the active switching part and an anthracene moiety as detector. We discuss the synthesis, the reversibility of the switch and the energy transfer properties of the new system.
Cubane Cross‐Coupling and Cubane–Porphyrin Arrays Bernhard, Stefan S. R.; Locke, Gemma M.; Plunkett, Shane ...
Chemistry : a European journal,
January 24, 2018, 2018-01-24, 20180124, Letnik:
24, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Invited for the cover of this issue is the group of Mathias O. Senge at Trinity College Dublin. The image depicts cubanes and new methods to attach functionalities onto the cubane core. Read the full ...text of the article at 10.1002/chem.201704344.
“Our interest in cubane arose not only from its aesthetic beauty, but also from its interesting properties.” Read more about the story behind the cover in the Cover Profile and about the research itself on page 1026 ff. (DOI: 10.1002/chem.201704344).
The preparation and characterization of an amperometric 2,4,6-trinitrotoluene (TNT) biosensor based on the surface immobilization of a maltose binding protein (MBP) nitroreductase (NR) fusion ...(MBP−NR) onto an electrode modified with an electropolymerized film of N-(3-pyrrol-1-ylpropyl)-4,4‘-bipyridine (PPB) are described. The MBP domain of MBP−NR exhibits a high and specific affinity toward electropolymerized films of PPB with the immobilized enzyme retaining virtually all of its enzymatic activity. Under similar conditions, the wild-type NR enzyme (i.e., without the MBP domain) loses most of its enzymatic activity. The kinetics of the catalytic reaction between the biosensor and TNT and 2,4-dinitrotoluene (DNT) were characterized using rotated disk electrode and cyclic voltammetry techniques, and values of 1.4 × 104 and 7.1 × 104 M-1 s-1 were obtained for TNT and DNT, respectively. The apparent Michaelis−Menten constants (K M) for MBP−NR in solution and on the surface, using TNT as substrate, were determined to be 27 and 95 μM, respectively. The corresponding value for “wild-type” NR in solution containing TNT was 78 μM, which is very close to the value obtained for MBP−NR on the surface. The limits of detection for both TNT and DNT were estimated to be 2 μM, and the sensitivities were determined to be 205 and 222 nA/μM, respectively.
Transient and variable phenomena in astrophysical sources are of particular importance to understand the underlying gamma-ray emission processes. In the very-high energy gamma-ray domain, transient ...and variable sources are related to charged particle acceleration processes that could for instance help understanding the origin of cosmic-rays. The imaging atmospheric Cherenkov technique used for gamma-ray astronomy above ~ 100 GeV is well suited for detecting such events. However, the standard analysis methods are not optimal for such a goal and more sensitive methods are specifically developed in this publication. The sensitivity improvement could therefore be helpful to detect brief and faint transient sources such as Gamma-Ray Bursts.
Cubane–aryl systems can now be achieved by using an improved nickel‐catalyzed redox‐active ester coupling strategy. After systematic investigations, the key obstacle of cubane cross‐coupling was ...identified and circumvented by altering the electron density of the transition metal through an adjusted choice of ligand. Furthermore, Sonogashira coupling of alkynyl‐arm‐extended cubanes was demonstrated by the synthesis of cubane–porphyrin arrays, proving the general compatibility of cubanes and Pd‐catalyzed cross‐coupling reactions. More information can be found in the Communication by M. O. Senge et al. on page 1026.
Enjoying the sun: The cover illustrates the potential of heterobimetallic AuI/RuII complexes to facilitate the P arylation of H‐phosphonates with diazonium salts, while visible light kicks off the ...dual gold and photoredox catalytic cycle. The underlying structure of the catalysts’ coordinating ligand system is accessible by a novel postfunctionalization approach, and the stereochemistry can be controlled by the order of metal coordination and click reaction. More information can be found in the Research Article by F. Breher and co‐workers (DOI: 10.1002/chem.202201856).
For most neurodegenerative diseases the precise duration of an individual cell's death is unknown, which is an obstacle when counteractive measures are being considered. To address this, we used the ...rd1 mouse model for retinal neurodegeneration, characterized by phosphodiesterase-6 (PDE6) dysfunction and photoreceptor death triggered by high cyclic guanosine-mono-phosphate (cGMP) levels. Using cellular data on cGMP accumulation, cell death, and survival, we created mathematical models to simulate the temporal development of the degeneration. We validated model predictions using organotypic retinal explant cultures derived from wild-type animals and exposed to the selective PDE6 inhibitor zaprinast. Together, photoreceptor data and modeling for the first time delineated three major cell death phases in a complex neuronal tissue: (1) initiation, taking up to 36 h, (2) execution, lasting another 40 h, and finally (3) clearance, lasting about 7 h. Surprisingly, photoreceptor neurodegeneration was noticeably slower than necrosis or apoptosis, suggesting a different mechanism of death for these neurons.
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