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Photolysis of α-carboxy-2-nitrobenzyl (CNB) caged compounds, studied here by time-resolved IR and UV spectroscopy, involves at least two pathways. In one, a conventional 2-nitrobenzyl type rearrangement takes place to release the photoprotected species via rapid decay of an aci-nitro intermediate. The α-carboxylate moiety of the CNB group is retained and the final by-product from this pathway is 2-nitrosophenylglyoxylate. Direct measurements of product formation confirmed that release via this pathway is faster for CNB-caged compounds than for related caged compounds without an α-carboxylate substituent and a rationale for the faster release rate is proposed. In a second pathway, photodecarboxylation of the starting material occurs: this pathway leads only to a slow, minor release of the photoprotected species. The extent to which the latter pathway contributes is affected by the nature of buffer salts in the irradiated solution. It was more prominent in an amine-based buffer (MOPS) than in phosphate buffer. [ABSTRACT FROM AUTHOR]

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Purpose: Activation of the myocardial, ATP-dependent potassium current (IKATP) during ischemia causes shortening of the action potential duration thereby increasing dispersion of repolarization between ischemic and non-ischemic myocardium and predisposing to reentrant arrhythmias. The IKATP inhibitor HMR1098 allows selective block of the sarcolemmal myocardial KATP-channel in various animal species. Therefore, we studied the concentration and pH-dependence of HMR1098 in human ventricular myocytes.Methods: Human ventricular cardiomyocytes were isolated enzymatically. IKATP was measured with the patch-clamp technique in whole cell configuration at 35°C. Action potentials were recorded using Amphotericine B in perforated patch conditions. In voltage clamp experiments, the KATP-channel was activated by application of 1μM rilmakalim, a KATP-channel opener. In action potential recordings, 0.1 μM rilmakalim was used.Results: At physiological pH (pH = 7.3) half-maximal block of the rilmakalim-induced current occurred at 0.42 ± 0.008 μM HMR1098 (at 0 mV membrane potential); under acidic conditions as can be expected to be present under ischemic conditions (pH = 6.5), half-maximal block was achieved at markedly lower concentrations (IC50 = 0.24 ± 0.009 μM). In current clamp experiments, block of IKATP by HMR1098 was capable of reversing the action potential shortening induced by rilmakalim, and restored the action potential plateau.Conclusions: HMR1098 appears to be useful to prevent IKATP-induced shortening of the action potential in human ventricular myocardium. More acidic conditions, as observed in ischemia, increase the sensitivity to HMR1098, indicating a more potent effect in ischemic myocardium. Thus, HMR1098 may be a useful agent to prevent action potential shortening and dispersion of repolarization during ischemia, which may protect against ischemia induced ventricular arrhythmias. [ABSTRACT FROM AUTHOR]

This work represents the first SQUID (superconducting quantum interference device) magnetometry study on the effect of incorporating beryllium into the synthesis of the high temperature superconductor Y Ba2Cu3O7 [?] d (Y123). Through a biopolymer-mediated synthetic approach, the homogeneous nature of the precursor sol and the preferred nucleation and growth of the Y123 phase allow for the greatest possible yield of the superconducting phase. In contrast to a previous report, our finding, through crystallographic studies of the as-synthesized material, is that in spite of a beryllium excess being provided in the precursor, beryllium does not substitute into the Y123 crystal lattice, instead forming an associate phase which comes to dominate at high doping levels, to the detriment of the Y123 phase. In addition, we are able unambiguously to refute the previously reported increase in superconducting transition temperature at low beryllium doping levels. [ABSTRACT FROM AUTHOR]