ERK signaling promotes resistance to TRK kinase inhibition in NTRK fusion-driven glioma mouse models.

Pediatric-type high-grade gliomas frequently harbor gene fusions involving receptor tyrosine kinase genes, including neurotrophic tyrosine kinase receptor (NTRK) fusions. Clinically, these tumors show high initial response rates to tyrosine kinase inhibition but ultimately recur due to the accumulation of additional resistance-conferring mutations. Here, we developed a series of genetically engineered mouse models of treatment-naïve and -experienced NTRK1/2/3 fusion-driven gliomas.

Impact of Intramolecular Hydrogen Bonding on the Reactivity of Cupric Superoxide Complexes with O-H and C-H Substrates.

The dioxygen reactivity of a series of TMPA-based copper(I) complexes (TMPA=tris(2-pyridylmethyl)amine), with and without secondary-coordination-sphere hydrogen-bonding moieties, was studied at -135 °C in 2-methyltetrahydrofuran (MeTHF). Kinetic stabilization of the H-bonded [( TMPA)Cu (O )] cupric superoxide species was achieved, and they were characterized by resonance Raman (rR) spectroscopy. The structures and physical properties of [( TMPA)Cu (N )] azido analogues were compared, and the O reactivity of ligand-Cu complexes when an H-bonding moiety is replaced by a methyl group was contrasted.

Enhanced Rates of C-H Bond Cleavage by a Hydrogen-Bonded Synthetic Heme High-Valent Iron(IV) Oxo Complex.

Secondary coordination sphere interactions are critical in facilitating the formation, stabilization, and enhanced reactivity of high-valent oxidants required for essential biochemical processes. Herein, we compare the C-H bond oxidizing capabilities of spectroscopically characterized synthetic heme iron(IV) oxo complexes, FCmpd-II (F = tetrakis(2,6-difluorophenyl)porphyrinate), and a 2,6-lutidinium triflate (LutH) Lewis acid adduct involving ferryl O-atom hydrogen-bonding, FCmpd-II(LutH). Second-order rate constants utilizing C-H and C-D substrates were obtained by UV-vis spectroscopic monitoring, while products were characterized and quantified by EPR spectroscopy and gas chromatography (GC).

Ligand Identity-Induced Generation of Enhanced Oxidative Hydrogen Atom Transfer Reactivity for a Cu(O) Complex Driven by Formation of a Cu(OOH) Compound with a Strong O-H Bond.

A superoxide-bridged dicopper(II) complex, [Cu(XYLO)(O)] () (XYLO = binucleating -xylyl derivative with a bridging phenolate ligand donor and two bis(2-{2-pyridyl}ethyl)amine arms), was generated from chemical oxidation of the peroxide-bridged dicopper(II) complex [Cu(XYLO)(O)] (), using ferrocenium (Fc) derivatives, in 2-methyltetrahydrofuran (MeTHF) at -125 °C. Using MeFc, a ⇆ equilibrium was established, allowing for calculation of the reduction potential of as -0.525 ± 0.

Unprecedented direct cupric-superoxo conversion to a bis--oxo dicopper(III) complex and resulting oxidative activity.

Investigations of small molecule copper-dioxygen chemistry can and have provided fundamental insights into enzymatic processes (e.g., copper metalloenzyme dioxygen binding geometries and their associated spectroscopy and substrate reactivity).

Spin Interconversion of Heme-Peroxo-Copper Complexes Facilitated by Intramolecular Hydrogen-Bonding Interactions.

Synthetic peroxo-bridged high-spin (HS) heme-(μ-η:η-O)-Cu(L) complexes incorporating (as part of the copper ligand) intramolecular hydrogen-bond (H-bond) capabilities and/or steric effects are herein demonstrated to affect the complex's electronic and geometric structure, notably impacting the spin state. An H-bonding interaction with the peroxo core favors a low-spin (LS) heme-(μ-η:η-O)-Cu(L) structure, resulting in a reversible temperature-dependent interconversion of spin state (5 coordinate HS to 6 coordinate LS). The LS state dominates at low temperatures, even in the absence of a strong trans-axial heme ligand.

Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function.

Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H/4e reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements.

Direct Determination of Electron-Transfer Properties of Dicopper-Bound Reduced Dioxygen Species by a Cryo-Spectroelectrochemical Approach.

Direct experimental determination of redox properties of superoxo (O ) and peroxo (O ) embedded in dicopper complexes bearing an unsymmetrical binucleating ligand was achieved using cryo-electrochemistry and cryo-spectroelectrochemistry in dichloromethane. Cyclic voltammetry for dicopper(I) (1 ) oxidation to a Cu Cu mixed-valent species (1 ) under inert atmosphere at 193 K reveals slow heterogeneous electron-transfer kinetics, indicative of a large reorganization energy. Oxygenation of the dicuprous complex 1 gives the bridged peroxo dicopper(II) species 3 , which is reversibly oxidized to the superoxo complex 2 at E =0.

Activation of dioxygen by copper metalloproteins and insights from model complexes.

Nature uses dioxygen as a key oxidant in the transformation of biomolecules. Among the enzymes that are utilized for these reactions are copper-containing metalloenzymes, which are responsible for important biological functions such as the regulation of neurotransmitters, dioxygen transport, and cellular respiration. Enzymatic and model system studies work in tandem in order to gain an understanding of the fundamental reductive activation of dioxygen by copper complexes.

Copper(I)-Dioxygen Adducts and Copper Enzyme Mechanisms.

Primary copper(I)-dioxygen (O) adducts, cupric-superoxide complexes, have been proposed intermediates in copper-containing dioxygen-activating monooxygenase and oxidase enzymes. Here, mechanisms of C-H activation by reactive copper-(di)oxygen intermediates are discussed, with an emphasis on cupric-superoxide species. Over the past 25 years, many synthetically derived cupric-superoxide model complexes have been reported.

Mutation scanning in a single and a stacked genetically modified (GM) event by real-time PCR and high resolution melting (HRM) analysis.

Genetic mutations must be avoided during the production and use of seeds. In the European Union (EU), Directive 2001/18/EC requires any DNA construct introduced via transformation to be stable. Establishing genetic stability is critical for the approval of genetically modified organisms (GMOs).

A 3-fold-symmetric ligand based on 2-hydroxypyridine: regulation of ligand binding by hydrogen bonding.

A tripodal ligand based on 2-hydroxypyridine is presented. Cu-Cl adducts of H3thpa with Cu(I) and Cu(II) provide complexes featuring highly directed, intramolecular hydrogen-bonding interactions. An upper limit for the hydrogen-bonding free energy to Cu(I)-Cl was estimated at ∼18 kcal/mol.

Molecular profiling--a tool for addressing emerging gaps in the comparative risk assessment of GMOs.

Assessing the risks of genetically modified organisms (GMOs) is required by both international agreement and domestic legislation. Many view the use of the "omics" tools for profiling classes of molecules as useful in risk assessment, but no consensus has formed on the need or value of these techniques for assessing the risks of all GMOs. In this and many other cases, experts support case-by-case use of molecular profiling techniques for risk assessment.

Resolution of symptoms of chronic constipation in an 8-year-old male after chiropractic treatment.

Objective: This case report describes the history, treatment, and proposed explanation of a positive outcome in a patient with chronic constipation.

Clinical Features: An 8-year-old boy presented with chronic constipation. His mother reported that this had been a problem since the child's birth.