Jeffrey E. Chen

Rheb is in a high activation state and inhibits B-Raf kinase in mammalian cells

Rheb (Ras homolog enriched in brain) is a member of the Ras family of proteins, and is in the immediate Ras/Rap/Ral subfamily. We found in three different mammalian cell lines that Rheb was highly activated, to levels much higher than for Ras or Rap 1, and that Rhebs activation state was unaffected by changes in growth conditions. Rhebs high activation was not secondary to unique glycine to arginine, or glycine to serine substitutions at positions 14 and 15, corresponding to Ras residues 12 and 13, since Rheb R14G and R14G, S15G mutants had similarly high activation levels as wild type Rheb. These data are consistent with earlier work which showed that purified Rheb has similar GTPase activity as Ras, and suggest a relative intracellular deficiency of Rheb GTPase activating proteins (GAPs) compared to Rheb activators. Further evidence for relatively low intracellular GAP activity was that increased Rheb expression led to a marked increase in Rheb activation. Rheb, like Ras and Rap1, bound B-Raf kinase, but in contrast to Ras and Rap 1, Rheb inhibited B-Raf kinase activity and prevented B-Raf-dependent activation of the transcription factor Elk-1. Thus, Rheb appears to be a unique member of the Ras/Rap/Ral subfamily, and in mammalian systems may serve to regulate B-Raf kinase activity.

A metal-free, high nitrogen-doped nanoporous graphitic carbon catalyst for an effective aerobic HMF-to-FDCA conversion

We report a metal-free catalysis of the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acids (FDCA), employing zeolitic-imidazole framework (ZIF-8) derived, nitrogen-doped nanoporous carbon (denoted as NNC) as an effective heterogeneous catalyst. The effect of high graphitic nitrogen loading in the NNC on the catalytic production of FDCA was demonstrated and discussed.

Medical Marijuana and Chronic Pain: a Review of Basic Science and Clinical Evidence.

Cannabinoid compounds include phytocannabinoids, endocannabinoids, and synthetics. The two primary phytocannabinoids are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), with CB1 receptors in the brain and peripheral tissue and CB2 receptors in the immune and hematopoietic systems. The route of delivery of cannabis is important as the bioavailability and metabolism are very different for smoking versus oral/sublingual routes. Gold standard clinical trials are limited; however, some studies have thus far shown evidence to support the use of cannabinoids for some cancer, neuropathic, spasticity, acute pain, and chronic pain conditions.

De Novo Synthesis of Gold-Nanoparticle-Embedded, Nitrogen-Doped Nanoporous Carbon Nanoparticles (Au@NC) with Enhanced Reduction Ability

A de novo synthesis of gold‐nanoparticle‐embedded, nitrogen‐doped nanoporous carbon nanoparticles (Au@NC) was investigated in this work. Chloroauroic acid was encapsulated inside zeolitic imidazolate framework‐8 (ZIF‐8) nanoparticles during the synthesis and later reduced into gold nanoparticles. The as‐synthesized gold‐nanoparticle‐embedded ZIF‐8 (Au@ZIF‐8) was then carbonized into Au@NC to enhance the stability of the nanoporous support. The results show that Au@NC exhibits a porous structure containing 3 wt % of gold. 2‐Methylimidazole provided an abundant amount of nitrogen (19 wt %) on the carbon matrix, which resulted in a hydrophilic and positively charged surface that is useful for the reduction of 4‐nitrophenol. The results of the catalytic reaction indicate that synthesized Au@NC could act as an effective catalyst with a turnover frequency (TOF) of 1185 g−1 s−1, which is higher than that of conventional naked Au nanoparticles (TOF: 339 g−1 s−1) and that of Au nanoparticles on activated carbon (TOF: 89 g−1 s−1). We propose that the enhanced performance of Au@NC resulted from homogeneous distribution of Au nanoparticles along with the hydrophilic and positively charged nitrogen‐doped carbon surface.

Synthesis of magnetic mesoporous titania colloidal crystals through evaporation induced self-assembly in emulsion as effective and recyclable photocatalysts.

This study illustrates the directed self-assembly of mesoporous TiO2 with magnetic properties due to its colloidal crystal structure with Fe3O4. The Fe3O4 nanoparticles were synthesized using co-precipitation techniques to a size of 28.2 nm and a magnetic saturation of 66.9 emu g(-1). Meanwhile, mesoporous titania nanoparticles (MTNs) with a particle diameter of 373 nm, a specific surface area of 236.3 m(2) g(-1), and a pore size of 2.8 nm were prepared by controlling the rate of hydrolysis. Magnetic colloidal crystals (a diameter of 10.2 μm) were formed by the aggregation of Fe3O4 and MTNs caused by the interface phenomena during solvent evaporation in emulsion. Even the anatase octahedrite produced from the colloidal crystal after a hydrothermal reaction retained a magnetic saturation of 2.8 emu g(-1). This study also investigates the photodegradation activity of our synthesized material as a photocatalyst, while utilizing its capability for magnetic separation to prove its usefulness in catalyst recycling.

Prussian Blue-Derived Synthesis of Hollow Porous Iron Pyrite Nanoparticles as Platinum-Free Counter Electrodes for Highly Efficient Dye-Sensitized Solar Cells

Iron pyrite has long been an attractive material for environmental and energy applications, but is hampered by a lack of control over morphology and purity. Hollow porous iron pyrite nanoparticles were synthesized by a direct sulfurization of iron oxide derived from Prussian blue. The high efficiencies of these hollow porous iron pyrite nanoparticles as effective dye-sensitized solar cell counter electrodes were demonstrated, with an efficiency of 7.31 %.

Proteomics studies of the interactome of RNA polymerase II C-terminal repeated domain.

AbstractBackgroundEukaryotic RNA polymerase II contains a C-terminal repeated domain (CTD) consisting of 52 consensus heptad repeats of Y1S2P3T4S5P6S7 that mediate interactions with many cellular proteins to regulate transcription elongation, RNA processing and chromatin structure. A number of CTD-binding proteins have been identified and the crystal structures of several protein-CTD complexes have demonstrated considerable conformational flexibility of the heptad repeats in those interactions. Furthermore, phosphorylation of the CTD at tyrosine, serine and threonine residues can regulate the CTD-protein interactions. Although the interactions of CTD with specific proteins have been elucidated at the atomic level, the capacity and specificity of the CTD-interactome in mammalian cells is not yet determined.ResultsA proteomic study was conducted to examine the mammalian CTD-interactome. We utilized six synthetic peptides each consisting of four consensus CTD-repeats with different combinations of serine and tyrosine phosphorylation as affinity-probes to pull-down nuclear proteins from HeLa cells. The pull-down fractions were then analyzed by MUDPIT mass spectrometry, which identified 100 proteins with the majority from the phospho-CTD pull-downs. Proteins pulled-down by serine-phosphorylated CTD-peptides included those containing the previously defined CTD-interacting domain (CID). Using SILAC mass spectrometry, we showed that the in vivo interaction of RNA polymerase II with the mammalian CID-containing RPRD1B is disrupted by CID mutation. We also showed that the CID from four mammalian proteins interacted with pS2-phosphorylated but not pY1pS2-doubly phosphorylated CTD-peptides. However, we also found proteins that were preferentially pulled-down by pY1pS2- or pY1pS5-doubly phosphorylated CTD-peptides. We prepared an antibody against tyrosine phosphorylated CTD and showed that ionizing radiation (IR) induced a transient increase in CTD tyrosine phosphorylation by immunoblotting. Combining SILAC and IMAC purification of phospho-peptides, we found that IR regulated the phosphorylation at four CTD tyrosine sites in different ways.ConclusionUpon phosphorylation, the 52 repeats of the CTD have the capacity to generate a large number of binding sites for cellular proteins. This study confirms previous findings that serine phosphorylation stimulates whereas tyrosine phosphorylation inhibits the protein-binding activity of the CTD. However, tyrosine phosphorylation of the CTD can also stimulate other CTD-protein interactions. The CTD-peptide affinity pull-down method described here can be adopted to survey the mammalian CTD-interactome in various cell types and under different biological conditions.

Intrathecal Ziconotide: Complications and Clinical Considerations

Ziconotide (Prialt) is available for intrathecal therapy for severe nociceptive and neuropathic chronic pain. It is a synthetic deviate of an omega-conotoxin, which is an N-type voltage-gated calcium channel inhibitor. It can be used alone or with combination therapy. The initial starting dose for ziconotide infusion is less than or equal to 2.4 mcg/day or 0.1 mcg/h and is recommended to be titrated slowly to help avoid adverse effects such as confusion and memory impairment.