chemical-vapor-deposition-an-organic-magnet-vanadium

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

Recent progress in the field of organic materials has yielded devices such as organic light emitting diodes (OLEDs) which have advantages not found in ...

The Ohio State University

Zero-Mode Waveguides were first introduced for Fluorescence Correlation Spectroscopy at micromolar dye concentrations. We show that combining zero-mode waveguides with fluorescence correlation spectroscopy in a continuous flow mixer avoids the compression of the FCS signal due to fluid transport at channel velocities up to approximately 17 mm/s. We derive an analytic scaling relationship [equation: see text] converting this flow velocity insensitivity to improved kinetic rate certainty in time-resolved mixing experiments. Thus zero-mode waveguides make FCS suitable for direct kinetics measurements in rapid continuous flow.

Single molecule correlation spectroscopy in continuous flow mixers with zero-mode waveguides.

The bacterial flagellar motor is a highly efficient rotary machine used by many bacteria to propel themselves. It has recently been shown that at low speeds its rotation proceeds in steps. Here we propose a simple physical model, based on the storage of energy in protein springs, that accounts for this stepping behavior as a random walk in a tilted corrugated potential that combines torque and contact forces. We argue that the absolute angular position of the rotor is crucial for understanding step properties and show this hypothesis to be consistent with the available data, in particular the observation that backward steps are smaller on average than forward steps. We also predict a sublinear speed versus torque relationship for fixed load at low torque, and a peak in rotor diffusion as a function of torque. Our model provides a comprehensive framework for understanding and analyzing stepping behavior in the bacterial flagellar motor and proposes novel, testable predictions. More broadly, the storage of energy in protein springs by the flagellar motor may provide useful general insights into the design of highly efficient molecular machines.

Steps in the bacterial flagellar motor.

We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E. coli motor at various pH and temperature conditions. In particular, the dramatic drop of torque at high rotation speeds (the "knee") is shown to arise from saturation of the proton flux. Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads. This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions.

Modeling torque versus speed, shot noise, and rotational diffusion of the bacterial flagellar motor.

Combination therapy of paclitaxel (taxol) with natural anti-tumor agents that are capable of inhibiting survival signals may provide a rational molecular basis for novel chemotherapeutic strategies. Our previous study showed that icariside II (IS), derived from Herba Epimedii, inhibited the proliferation of melanoma cells in vivo and in vitro through the regulation of apoptosis. In this report, the combination effects of paclitaxel and IS were investigated in human melanoma A375 cells. As compared to the treatment with paclitaxel alone, the co-administration of IS and paclitaxel resulted in an enhancement of apoptosis as revealed by WST-8 and PI assays. Meanwhile, Western blot analysis showed that the co-administration of IS and paclitaxel resulted in increases of cleaved caspase-3, one of the terminal pro-apoptotic proteins. In melanoma, IL-8 and VEGF are positively correlated with disease stage and a high probability of progression. We demonstrated that treatment of A375 cells with IS in combination with paclitaxel resulted in a significant decrease in the production of IL-8 and VEGF, compared with paclitaxel alone. Recent studies suggest that TLR4-MyD88-ERK signaling may be a novel target for reversing chemoresistance to paclitaxel. Our flow cytometry and Western blot data showed that paclitaxel activated TLR4-MyD88-ERK signaling and that IS treatment could effectively inhibit this paclitaxel-induced activation of TLR4-MyD88-ERK signaling. In conclusion, this study demonstrated for the first time that IS could potentiate paclitaxel-induced apoptosis in melanoma cells. These effects were mediated, at least in part, by inhibiting the activation of the TLR4 signal transduction pathways. These findings support further preclinical evaluation of IS as a new potential anti-tumor agent.

Icariside II potentiates paclitaxel-induced apoptosis in human melanoma A375 cells by inhibiting TLR4 signaling pathway.

The preparation and characterization of a new thin-film organic-based magnet V[MeTCEC]x (V = vanadium; MeTCEC = methyl tricaynoethylenecarboxylate) via low-temperature chemical vapor deposition (50 °C) is reported. These thin films exhibit room-temperature magnetic ordering and semiconducting behavior, demonstrating the ability of tuning their magnetic, and potentially spintronic, functionality via chemical modification of the organic ligand.

Article	Year
Single molecule correlation spectroscopy in continuous flow mixers with zero-mode waveguides. Optics express\| PubMed ID: 18607415	2008
Steps in the bacterial flagellar motor. PLoS computational biology\| PubMed ID: 19851449	2009
Modeling torque versus speed, shot noise, and rotational diffusion of the bacterial flagellar motor. Physical review letters\| PubMed ID: 20366231	2009
Icariside II potentiates paclitaxel-induced apoptosis in human melanoma A375 cells by inhibiting TLR4 signaling pathway. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association\| PubMed ID: 22743248	2012
Thin-film deposition of an organic magnet based on vanadium methyl tricyanoethylenecarboxylate. Advanced materials (Deerfield Beach, Fla.)\| PubMed ID: 25327816	2014

Howard Yu

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