Quasiparticle scattering and local density of states in the d-density wave phase

We study the effects of single-impurity scattering on the local density of states in the high-$T_c$ cuprates. We compare the quasiparticle interference patterns in three different ordered states: d-wave superconductor (DSC), d-density wave (DDW), and coexisting DSC and DDW (DSC-DDW). In the coexisting state, at energies below the DSC gap, the patterns are almost identical to those in the pure DSC state with the same DSC gap. However, they are significantly different for energies greater than or equal to the DSC gap. This transition at an energy around the DSC gap can be used to test the nature of the superconducting state of the underdoped cuprates by scanning tunneling microscopy. Furthermore, we note that in the DDW state the effect of the coherence factors is stronger than in the DSC state. The new features arising due to DDW ordering are discussed.Comment: 6 page, 5 figures (Higher resolution figures are available by request

Tubulin isoform composition tunes microtubule dynamics

Microtubules polymerize and depolymerize stochastically, a behavior essential for cell division, motility and differentiation. While many studies advanced our understanding of how microtubule-associated proteins tune microtubule dynamics in trans, we have yet to understand how tubulin genetic diversity regulates microtubule functions. The majority of in vitro dynamics studies are performed with tubulin purified from brain tissue. This preparation is not representative of tubulin found in many cell types. Here we report the 4.2Å cryo-EM structure and in vitro dynamics parameters of α1B/βI+βIVb microtubules assembled from tubulin purified from a human embryonic kidney cell line with isoform composition characteristic of fibroblasts and many immortalized cell lines. We find that these microtubules grow faster and transition to depolymerization less frequently compared to brain microtubules. Cryo-EM reveals that the dynamic ends of α1B/βI+βIVb microtubules are less tapered and that these tubulin heterodimers display lower curvatures. Interestingly, analysis of EB1 distributions at dynamic ends suggests no differences in GTP cap sizes. Lastly, we show that the addition of recombinant α1A/βIII tubulin, a neuronal isotype overexpressed in many tumors, proportionally tunes the dynamics of α1B/βI+βIVb microtubules. Our study is an important step towards understanding how tubulin isoform composition tunes microtubule dynamics

A New Strategy for Glioblastoma Treatment: In Vitro and In Vivo Preclinical Characterization of Si306, a Pyrazolo[3,4-d]Pyrimidine Dual Src/P-Glycoprotein Inhibitor

20siopenOverexpression of P-glycoprotein (P-gp) and other ATP-binding cassette (ABC) transporters in multidrug resistant (MDR) cancer cells is responsible for the reduction of intracellular drug accumulation, thus decreasing the efficacy of chemotherapeutics. P-gp is also found at endothelial cells' membrane of the blood-brain barrier, where it limits drug delivery to central nervous system (CNS) tumors. We have previously developed a set of pyrazolo[3,4-d]pyrimidines and their prodrugs as novel Src tyrosine kinase inhibitors (TKIs), showing a significant activity against CNS tumors in in vivo. Here we investigated the interaction of the most promising pair of drug/prodrug with P-gp at the cellular level. The tested compounds were found to increase the intracellular accumulation of Rho 123, and to enhance the efficacy of paclitaxel in P-gp overexpressing cells. Encouraging pharmacokinetics properties and tolerability in vivo were also observed. Our findings revealed a novel role of pyrazolo[3,4-d]pyrimidines which may be useful for developing a new effective therapy in MDR cancer treatment, particularly against glioblastoma.openFallacara, Anna Lucia; Zamperini, Claudio; Podolski-Renić, Ana; Dinić, Jelena; Stanković, Tijana; Stepanović, Marija; Mancini, Arianna; Rango, Enrico; Iovenitti, Giulia; Molinari, Alessio; Bugli, Francesca; Sanguinetti, Maurizio; Torelli, Riccardo; Martini, Maurizio; Maccari, Laura; Valoti, Massimo; Dreassi, Elena; Botta, Maurizio; Pešić, Milica; Schenone, SilviaFallacara, Anna Lucia; Zamperini, Claudio; Podolski-Renić, Ana; Dinić, Jelena; Stanković, Tijana; Stepanović, Marija; Mancini, Arianna; Rango, Enrico; Iovenitti, Giulia; Molinari, Alessio; Bugli, Francesca; Sanguinetti, Maurizio; Torelli, Riccardo; Martini, Maurizio; Maccari, Laura; Valoti, Massimo; Dreassi, Elena; Botta, Maurizio; Pešić, Milica; Schenone, Silvi

The Role of Actin Turnover in Retrograde Actin Network Flow in Neuronal Growth Cones

The balance of actin filament polymerization and depolymerization maintains a steady state network treadmill in neuronal growth cones essential for motility and guidance. Here we have investigated the connection between depolymerization and treadmilling dynamics. We show that polymerization-competent barbed ends are concentrated at the leading edge and depolymerization is distributed throughout the peripheral domain. We found a high-to-low G-actin gradient between peripheral and central domains. Inhibiting turnover with jasplakinolide collapsed this gradient and lowered leading edge barbed end density. Ultrastructural analysis showed dramatic reduction of leading edge actin filament density and filament accumulation in central regions. Live cell imaging revealed that the leading edge retracted even as retrograde actin flow rate decreased exponentially. Inhibition of myosin II activity before jasplakinolide treatment lowered baseline retrograde flow rates and prevented leading edge retraction. Myosin II activity preferentially affected filopodial bundle disassembly distinct from the global effects of jasplakinolide on network turnover. We propose that growth cone retraction following turnover inhibition resulted from the persistence of myosin II contractility even as leading edge assembly rates decreased. The buildup of actin filaments in central regions combined with monomer depletion and reduced polymerization from barbed ends suggests a mechanism for the observed exponential decay in actin retrograde flow. Our results show that growth cone motility is critically dependent on continuous disassembly of the peripheral actin network

U.S. Department of Energy Polymer Electrolyte Membrane Fuel Cell Catalyst Development Activities

The U.S. Department of Energy's (DOE's) Fuel Cell Technologies Program supports research and development of electrocatalysts for polymer electrolyte membrane fuel cells. R&amp;D projects address cost, durability, and performance with the goal of reducing or eliminating platinum group metals from the catalysts. The projects' strategies include: ultra-low platinum loading, platinum alloy catalysts, novel architectures, and non-PGM catalysts. The deposition of Pt monolayers on Pd nanoparticles was improved by displacement of Pd by Pt; the catalyst activity is comparable to those fabricated using Cu underpotential deposition. The specific activity of nanoparticles can be improved by ~4x using ternary alloys. Catalysts, prepared with excess non-noble elements that are removed during processing, i.e., dealloying, attain a mass activity exceeding that of commercial catalysts. Extended catalyst surfaces on nanotubes, nanowires, and metal oxides have been developed. Results from DOE's catalyst projects will be discussed in detail.</jats:p