Ultrafast UV pump/IR probe studies of C-H activation in linear,cyclic, and aryl hydrocarbons

The photochemical C-H activation reactions of eta(3)-TpRh(CO)(2) (Tp = HB-Pz(3), Pz = 3,5-dimethylpyrazolyl) and CpRh(CO)(2) (Cp = C(5)H(5)) have been studied in a series of linear, cyclic, and aromatic hydrocarbon solvents on a femtosecond to microsecond time scale. These results have revealed that the structure of the hydrocarbon substrate affects the final C-H bond activation step, which is in accordance with the known preference of bond activation toward primary C-H sites. In the case of aromatic C-H activation, the reaction is divided into parallel channels involving sigma- and pi-solvated intermediates. Results for the analogous CpRh(CO)(2) molecule have shown that the coordination of the cyclopentadienyl ligand does not play a direct role in the dynamics of the reaction, in contrast to the C-H activation mechanism observed in eta(3)-TpRh(CO)(2) studies.     

Identification of Tumor Initiating Cells with a Small‐Molecule Fluorescent Probe by Using Vimentin as a Biomarker

Tumor initiating cells (TICs) have been implicated in clinical relapse and metastasis of a variety of epithelial cancers, including lung cancer. While efforts toward the development of specific probes for TIC detection and targeting are ongoing, a universal TIC probe has yet to be developed. We report the first TIC‐specific fluorescent chemical probe, TiY, with identification of the molecular target as vimentin, a marker for epithelial‐to‐mesenchymal transition (EMT). TiY selectively stains TICs over differentiated tumor cells or normal cells, and facilitates the visualization and enrichment of functionally active TICs from patient tumors. At high concentration, TiY also shows anti‐TIC activity with low toxicity to non‐TICs. With the unexplored target vimentin, TiY shows potential as a first universal probe for TIC detection in different cancers.     

Functionalization of zeolite ZSM-5 by hydrosilylation and acetone coupling: synthesis, MAS NMR, and theory

We report a two-step postsynthetic functionalization reaction of zeolite HZSM-5 that proceeds with high selectivity at room temperature. In the first step the framework acid sites of the zeolite are reacted with phenylsilane to replace the acidic proton with a hydrosilyl (-SiH3) group covalently linked to the framework. This group readily couples to acetone in a second step to form a framework-bound hydrosilyl isopropyl ether that is thermally stable at 473 K, but decomposes in the presence of moisture. We characterized these reactions using 29Si, 1H, and 13C MAS NMR, as appropriate. Theoretical modeling using density functional theory and cluster models of the zeolite acid site confirmed that both steps were exothermic and provided theoretical chemical shift values in excellent agreement with experiment.     

Impedance Analysis of Single Melanoma Cells in Microfluidic Devices

The electrical impedance analysis of single cells can provide information on cells’ pathological condition in various environments. Cell electrical properties are affected by factors such as the location, adhesion, and size of the cell. The proposed microfluidic device captures a single cell, maintains growth conditions, and allows single‐melanoma‐cell impedance to be measured using an impedance analyzer and a function generator. The rate of impedance variation (ROIV) can be used to determine cell growth conditions. Cellular apoptosis affects cell size and membrane surface area, and thus the electrical properties of cells. At 24 h without Antrodia cinnamomea (AC) addition, ROIV was 15.23 %, 17.04 %, and 12.60 % at temperatures of 34 °C, 37 °C, and 40 °C, respectively. At 24 h and 37 °C, ROIV was 17.04 %, 40.37 %, and 45.02 % for AC concentrations of 0, 20, and 40 µL/mL, respectively. The results show that the cell impedance variation of cells cultured without AC is much lower than that of cells cultured with AC. Regarding cellular morphology, with AC addition, the cells shrank obviously after 24 h, whereas they barely shrank without AC addition.     

Fluorescent Hydroxylamine Derived from the Fragmentation of PAMAM Dendrimers for Intracellular Hypochlorite Recognition

Herein, a promising sensing approach based on the structure fragmentation of poly(amidoamine) (PAMAM) dendrimers for the selective detection of intracellular hypochlorite (OCl^?) is reported. PAMAM dendrimers were easily disrupted by a cascade of oxidations in the tertiary amines of the dendritic core to produce an unsaturated hydroxylamine with blue fluorescence. Specially, the novel fluorophore was only sensitive to OCl^?, one of reactive oxygen species (ROS), resulting in an irreversible fluorescence turn‐off. The fluorescent hydroxylamine was selectively oxidised by OCl^? to form a labile oxoammonium cation that underwent further degradation. Without using any troublesomely synthetic steps, the novel sensing platform based on the fragmentation of PAMAM dendrimers, can be applied to detect OCl^? in macrophage cells. The results suggest that the sensing approach may be useful for the detection of intracellular OCl^? with minimal interference from biological matrixes.     

Core-level positive-ion and negative-ion fragmentation of gaseous and condensed HCCl3 using synchrotron radiation

We investigated the dissociation dynamics of positive-ion and negative-ion fragments of gaseous and condensed HCCl(3) following photoexcitation of Cl 2p electrons to various resonances. Based on ab initio calculations at levels HF/cc-pVTZ and QCISD/6-311G?, the first doublet structures in Cl L-edge x-ray absorption spectrum of HCCl(3) are assigned to transitions from the Cl (2P(3/2),(1/2)) initial states to the 10a(1)(?) orbitals. The Cl 2p → 10a(1)(?) excitation of HCCl(3) induces a significant enhancement of the Cl(+) desorption yield in the condensed phase and a small increase in the HCCl(+) yield in the gaseous phase. Based on the resonant photoemission of condensed HCCl(3), excitations of Cl 2p electrons to valence orbitals decay predominantly via spectator Auger transitions. The kinetic energy distributions of Cl(+) ion via the Cl 2p → 10a(1)(?) excitation are shifted to higher energy ～0.2 eV and ～0.1 eV relative to those via the Cl 2p → 10e(?) excitation and Cl 2p → shape resonance excitation, respectively. The enhancement of the yields of ionic fragments at specific core-excited resonance states is assisted by a strongly repulsive surface that is directly related to the spectator electrons localized in the antibonding orbitals. The Cl(-) anion is significantly reinforced in the vicinity of Cl 2p ionization threshold of gaseous HCCl(3), mediated by photoelectron recapture through post-collision interaction.