Self-Absorption and Luminescence Quantum Yields of Dye-Zeolite L Composites

Electronic absorption and fluorescence spectra based on transmission measurements of thin layers obtained from new perylene−zeolite L composites and new dye1,dye2−zeolite L sandwich composites, the latter acting as antenna systems, have been investigated and analyzed. The influence of extra- and intraparticle self-absorption on the spectral shape and fluorescence quantum yield is discussed in detail. Due to its intraparticle origin, self-absorption and re-emission can often not be avoided in organized systems such as dye−zeolite L composites where a high density of chromophores is a prerequisite for obtaining the desired photophysical properties. We show, however, that it can be avoided or at least minimized by preparing dye1,dye2−zeolite L sandwich composites where donors are present in a much larger amount than the acceptors because they act as antenna systems.

Charge Transport in Photoswitchable Dimethyldihydropyrene-Type Single-Molecule Junctions

The conductance properties of a photoswitchable dimethyldihydropyrene (DHP) derivative have been investigated for the first time in single-molecule junctions using the mechanically controllable break junction technique. We demonstrate that the reversible structure changes induced by isomerization of a single bispyridine-substituted DHP molecule are correlated with a large drop of the conductance value. We found a very high ON/OFF ratio (>104) and an excellent reversibility of conductance switching.

Single-Molecule Conductance of Functionalized Oligoynes: Length Dependence and Junction Evolution

We report a combined experimental and theoretical investigation of the length dependence and anchor group dependence of the electrical conductance of a series of oligoyne molecular wires in single-molecule junctions with gold contacts. Experimentally, we focus on the synthesis and properties of diaryloligoynes with n = 1, 2, and 4 triple bonds and the anchor dihydrobenzo[b]thiophene (BT). For comparison, we also explored the aurophilic anchor group cyano (CN), amino (NH2), thiol (SH), and 4-pyridyl (PY). Scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single-molecule conductance characteristics. The BT moiety is superior as compared to traditional anchoring groups investigated so far. BT-terminated oligoynes display a 100% probability of junction formation and possess conductance values which are the highest of the oligoynes studied and, moreover, are higher than other conjugated molecular wires of similar length. Density functional theory (DFT)-based calculations are reported for oligoynes with n = 1−4 triple bonds. Complete conductance traces and conductance distributions are computed for each family of molecules. The sliding of the anchor groups leads to oscillations in both the electrical conductance and the binding energies of the studied molecular wires. In agreement with experimental results, BT-terminated oligoynes are predicted to have a high electrical conductance. The experimental attenuation constants βH range between 1.7 nm−1 (CN) and 3.2 nm−1 (SH) and show the following trend: βH(CN) < βH(NH2) < βH(BT) < βH(PY) ≈ βH(SH). DFT-based calculations yield lower values, which range between 0.4 nm−1 (CN) and 2.2 nm−1 (PY).

Oligo(aryleneethynylene)s with Terminal Pyridyl Groups: Synthesis and Length Dependence of the Tunneling-to-Hopping Transition of Single-Molecule Conductances

The synthesis is reported of a new series of oligo(aryleneethynylene) (OAE) derivatives of up to ca. 6 nm in molecular length (OAE9) using iterative Pd-mediated Sonogashira cross-coupling methodology. The oligo-p-phenyleneethynylene cores of the molecular wires are functionalized at both termini with pyridyl units for attachment to gold leads. The molecular structures determined by single-crystal X-ray analysis are reported for OAE4, OAE5, OAE7, and OAE8a. The charge transport characteristics of derivatives OAE3–OAE9 in single-molecular junctions have been studied using the mechanically controlled break junction technique. The data demonstrate that the junction conductance decreases with increasing molecular length. A transition from coherent transport via tunneling to a hopping mechanism is found for OAE wires longer than ca. 3 nm.

Benzo1,2-b:4,5-b 'difuran-based sensitizers for dye-sensitized solar cells

Two BDF-based organic sensitizers, as first examples for their use in dye-sensitized solar cells, are prepared and characterized. They yield promising power conversion efficiencies of up to 5.5 and high open circuit voltages up to 0.82 V. This work demonstrates that the BDF chromophore acts as an effective donor in organic sensitizers.

Vascular cell adhesion molecule 1 expression by biliary epithelium promotes persistence of inflammation by inhibiting effector T-cell apoptosis

Chronic hepatitis occurs when effector lymphocytes are recruited to the liver from blood and retained in tissue to interact with target cells, such as hepatocytes or bile ducts (BDs). Vascular cell adhesion molecule 1 (VCAM-1; CD106), a member of the immunoglobulin superfamily, supports leukocyte adhesion by binding a4b1 integrins and is critical for the recruitment of monocytes and lymphocytes during inflammation. We detected VCAM-1 on cholangiocytes in chronic liver disease (CLD) and hypothesized that biliary expression of VCAM-1 contributes to the persistence of liver inflammation. Hence, in this study, we examined whether cholangiocyte expression of VCAM-1 promotes the survival of intrahepatic a4b1 expressing effector T cells. We examined interactions between primary human cholangiocytes and isolated intrahepatic T cells ex vivo and in vivo using the Ova-bil antigen-driven murine model of biliary inflammation. VCAM-1 was detected on BDs in CLDs (primary biliary cirrhosis, primary sclerosing cholangitis, alcoholic liver disease, and chronic hepatitis C), and human cholangiocytes expressed VCAM-1 in response to tumor necrosis factor alpha alone or in combination with CD40L or interleukin-17. Liver-derived T cells adhered to cholangiocytes in vitro by a4b1, which resulted in signaling through nuclear factor kappa B p65, protein kinase B1, and p38 mitogen-activated protein kinase phosphorylation. This led to increased mitochondrial B-cell lymphoma 2 accumulation and decreased activation of caspase 3, causing increased cell survival. We confirmed our findings in a murine model of hepatobiliary inflammation where inhibition of VCAM-1 decreased liver inflammation by reducing lymphocyte recruitment and increasing CD8 and T helper 17 CD4 Tcell survival. Conclusions: VCAM-1 expression by cholangiocytes contributes to persistent inflammation by conferring a survival signal to a4b1 expressing proinflammatory T lymphocytes in CLD.

Targeting of the MET receptor tyrosine kinase by small molecule inhibitors leads to MET accumulation by impairing the receptor downregulation.

The MET receptor tyrosine kinase is deregulated primarily via overexpression or point mutations in various human cancers and different strategies for MET inhibition are currently evaluated in clinical trials. We observed by Western blot analysis and by Flow cytometry that MET inhibition by different MET small molecule inhibitors surprisingly increases in a dose-dependent manner total MET levels in treated cells. Mechanistically, this inhibition-related MET accumulation was associated with reduced Tyr1003 phosphorylation and MET physical association with the CBL ubiquitin ligase with concomitant decrease in MET ubiquitination. These data may suggest careful consideration for design of anti-MET clinical protocols.