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Synthesis and Properties of a pH‐Insensitive Fluorescent Nitric Oxide Cheletropic Trap (FNOCT)

The synthesis and properties of the new fluorescent nitric oxide cheletropic trap (FNOCT) 14 , designed for the trapping and quantification of nitric oxide (NO) production in chemical and biological systems, is described (Scheme 3). The dicarboxylic acid 14 and the corresponding bis[(acetyloxy)methyl] ester derivative 15 of the FNOCT contain a 2‐methoxy‐substituted phenanthrene group as fluorophoric unit. The fluorescence of the reduced NO adduct of this FNOCT (λ_exc 320 nm, λ_em 380 nm) is pH‐independent. Trapping experiments were carried out in aqueous buffer solution at pH 7.4 with nitric oxide being added as a bolus as well as being released from the NO donor compound MAHMA NONOate (= (1Z)‐1‐{methyl[6‐(methylammonio)hexyl]amino}diazen‐1‐ium‐1,2‐diolate), indicating a trapping efficiency of ca. 50%. In a biological application, nitric oxide was scavenged from a culture of lipopolysaccharide‐stimulated rat alveolar macrophages. Under the applied conditions, a production of 11.1 ± 1.5 nmol of NO per hour and per 10⁵ cells was estimated.     

Spatiotemporal Control of CRISPR/Cas9 Function in Cells and Zebrafish using Light‐Activated Guide RNA

We developed a new method for the conditional regulation of CRISPR/Cas9 activity in mammalian cells and zebrafish embryos using photochemically activated, caged guide RNAs (gRNAs). Caged gRNAs are generated by substituting four nucleobases evenly distributed throughout the 5′‐protospacer region with caged nucleobases during synthesis. Caging confers complete suppression of gRNA:dsDNA‐target hybridization and rapid restoration of CRISPR/Cas9 function upon optical activation. This tool offers simplicity and complete programmability in design, high spatiotemporal specificity in cells and zebrafish embryos, excellent off‐to‐on switching, and stability by preserving the ability to form Cas9:gRNA ribonucleoprotein complexes. Caged gRNAs are novel tools for the conditional control of gene editing, thereby enabling the investigation of spatiotemporally complex physiological events by obtaining a better understanding of dynamic gene regulation.     

Spatiotemporal Control of CRISPR/Cas9 Function in Cells and Zebrafish using Light-Activated Guide RNA

We developed a new method for the conditional regulation of CRISPR/Cas9 activity in mammalian cells and zebrafish embryos using photochemically activated, caged guide RNAs (gRNAs). Caged gRNAs are generated by substituting four nucleobases evenly distributed throughout the 5′-protospacer region with caged nucleobases during synthesis. Caging confers complete suppression of gRNA:dsDNA-target hybridization and rapid restoration of CRISPR/Cas9 function upon optical activation. This tool offers simplicity and complete programmability in design, high spatiotemporal specificity in cells and zebrafish embryos, excellent off-to-on switching, and stability by preserving the ability to form Cas9:gRNA ribonucleoprotein complexes. Caged gRNAs are novel tools for the conditional control of gene editing, thereby enabling the investigation of spatiotemporally complex physiological events by obtaining a better understanding of dynamic gene regulation.     

Simulation of pressure pulsations in the breathing circuit of a deep-sea diving system by using the four-pole method

A method for calculating pressure pulsations in compressor and engine manifolds known as the “four-pole method” is applied to the breathing circuit of a deep-sea diving system. The response of the diver's helmet to the input of two banks of compressors is formulated. A computer is used to solve the response equation and generate the sound pressure level spectrum in the helmet. Results are shown to be in good agreement with experimental data. The computer simulation is used to examine the effects of such parameters as diver's depth, breathing gas flow rate, cylinder bank phasing and system geometry.