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1.
Understanding oxygen fluctuation in a cancerous tumor is important for effective treatment, especially during radiotherapy. In this paper, ruthenium complexes bearing a nitroimidazole group are shown to report the oxygen status in tumor tissue directly. The nitroimidazole group was known to be accumulated in hypoxic tumor tissues. On the other hand, the ruthenium complex showed strong phosphorescence around 600 nm. The emission of ruthenium is quenched instantaneously by molecular oxygen due to energy transfer between triplet states of oxygen and ruthenium complex, but the emission is then recovered by the removal of oxygen. Thus, we could observe oxygen fluctuation in tumor tissue in a real‐time manner by monitoring the phosphorescence of the ruthenium complex. The versatility of the probe is demonstrated by monitoring oxygen fluctuation in living cells and tumor tissue planted in mice. The ruthenium complex promptly penetrated plasma membrane and accumulated in cells to emit its oxygen‐dependent phosphorescence. In vivo experiments revealed that the oxygen level in tumor tissue seems to fluctuate at the sub‐minute timescale.  相似文献   
2.
Despite the long history of polyaniline chemistry, backbone‐substituted polyanilines are limited. Here, we report the synthesis of pentiptycene‐incorporated polyanilines through acidic aniline oxidative polymerization with three pentiptycene derivatives, TA, DA, and TP, as nucleate additives. The reactivity of TA > DA ? TP, as evidenced by structural and property analysis of the corresponding polyaniline products, demonstrates a radical coupling mechanism and the formation of Dewar π‐complex intermediates for the chain propagation. In addition, the iptycene substituent effect on enhancing the electrochemical stability and charge storage capability of polyaniline are discussed with a clip model, namely, the threading of neighboring polyaniline chains through the U‐ and V‐shaped cavities of pentiptycene restricts lateral motions of the polymer chains and promotes interchain conductivity. Density function theory (DFT) calculations suggest a larger clipping effect for the U versus V cavities. Both the conclusion of a terminal planar p‐phenylenediamine (ppda) group being the key component of an effective nucleate and the concept of interchain clipping for enhanced electrochemical performance should facilitate the design and synthesis of novel polyanilines for electronic applications.  相似文献   
3.
Transport in Porous Media - A concise and accurate prediction method is required for membrane permeability in chemical engineering and biological fields. As a preliminary study on this topic, we...  相似文献   
4.
Carquinostatin A (CQS), a potent neuroprotective substance, is a unique carbazole alkaloid with both an ortho‐quinone function and an isoprenoid moiety. We identified the entire gene cluster responsible for CQS biosynthesis in Streptomyces exfoliatus through heterologous production of CQS and gene deletion. Biochemical characterization of seven CQS biosynthetic gene products (CqsB1–7) established the total biosynthetic pathway of CQS. Reconstitution of CqsB1 and CqsB2 showed that the synthesis of the carbazole skeleton involves CqsB1‐catalyzed decarboxylative condensation of an α‐hydroxyl‐β‐keto acid intermediate with 3‐hydroxybutyryl‐ACP followed by CqsB2‐catalyzed oxidative cyclization. Based on crystal structures and mutagenesis‐based biochemical assays, a detailed mechanism for the unique deprotonation‐initiated cyclization catalyzed by CqsB2 is proposed. Finally, analysis of the substrate specificity of the biosynthetic enzymes led to the production of novel carbazoles.  相似文献   
5.
Physics of the Solid State - Transition metal doped cesium lead halide (CsPbI3) perovskite compounds were studied for application in photovoltaic solar cells. Electronic structures, chemical shifts...  相似文献   
6.
This work examines the ozone electrogeneration(OE) at a binary coating of different nominal compositions(Pt)x-(TaOy)(100-x), where x(percentage in the precursor solution) varied between 1% and 100%, coated on titanium substrate prepared by a sol-gel technique. TheOE is performed in an artificial tap water at room temperature(25C). The percentages of Pt and TaOy in the coating significantly affect the electrocatalytic activity towards oxygen evolution. The oxygen evolution was retarded to a different extent based on the electrode composition. The largest retardation was obtained at the(Pt)10-(TaOy)90 electrode(ca. 480 m V positive shift) as compared with the(Pt)100-(TaOy)0 electrode.This was reflected in a high current efficiency(CE) ofOE(ca. 19.3%) at the former electrode. This value is considered to be among the highest values reported forOE at 25C in neutral media. The composite electrodes were characterized by voltammetric and surface techniques. A plausible explanation for the change of the efficiency ofOE with the electrode composition is given based on the electrochemical results.  相似文献   
7.
8.
Tandem C?C bond formation was achieved through silver‐catalyzed ring‐opening of cyclopropenes via carbene intermediates. The reaction of cyclopropenes in the presence of a silver catalyst gave indene derivatives under ambient conditions. In contrast, the insertion of organozinc reagents to silver carbene or allylic cation intermediates afforded allylmetal intermediates for the tandem allylation of carbonyl compounds.  相似文献   
9.
A series of xanthone and thioxanthone derivatives with aminoalkoxy substituents were synthesized as fluorescent indicators for a displacement assay in the study of small‐molecule–RNA interactions. The RNA‐binding properties of these molecules were investigated in terms of the improved binding selectivity to the loop region in the RNA secondary structure relative to 2,7‐bis(2‐aminoethoxy)xanthone (X2S) by fluorimetric titration and displacement assay. An 11‐mer double‐stranded RNA and a hairpin RNA mimicking the stem loop IIB of Rev response element (RRE) RNA of HIV‐1 mRNA were used. The X2S derivatives with longer aminoalkyl substituents showed a higher affinity to the double‐stranded RNA than the parent molecule. Introduction of a methyl group on the aminoethoxy moiety of X2S effectively modulated the selectivity to the RNA secondary structure. Methyl group substitution at the C1′ position suppressed the binding to the loop regions. Substitution with two methyl groups on the amino nitrogen atom resulted in reducing the affinity to the double‐stranded region by a factor of 40 %. The effect of methyl substitution on the amino nitrogen atom was also observed for a thioxanthone derivative. Titration experiments, however, suggested that thioxanthone derivatives showed a more prominent tendency of multiple binding to RNA than xanthone derivatives. The selectivity index calculated from the affinity to the double‐stranded and loop regions suggested that the N,N‐dimethyl derivative of X2S would be suitable for the screening of small molecules binding to RRE.  相似文献   
10.
We have developed two syntheses of vicenistatin and its analogues. Our first‐generation strategy included the rapid and sequential assembly of the macrocyclic lactam by using an intermolecular Horner–Wadsworth–Emmons reaction between the C3–C13 fragment and the C1–C2, C14–C19 fragment, followed by an intramolecular Stille coupling reaction. The second‐generation strategy utilized a ring‐closing metathesis of a hexaene intermediate to generate the desired 20‐membered macrolactam. This second‐generation strategy made it possible to prepare synthetic analogues of vicenistatin, including the C20‐ and/or C23‐demethyl analogues. Evaluation of the cytotoxic effect of these analogues indicated the importance of the fixed conformation of aglycon for determining the biological activity of the vicenistatins.  相似文献   
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