A method for preparation of a new stable Cu(I) catalyst supported on weakly acidic polyacrylate resin without additional stabilizing ligands is described. A simple and efficient methodology for Ullmann Cu(I) catalyzed C-N cross coupling reactions using this original catalyst is reported. Coupling reactions of 4-chloropyridinium chloride with anilines containing electron donating (EDG) or electron withdrawing (EWG) groups, naphthalen-2-amine and piperazine, respectively, are successfully demonstrated.
- MeSH
- 2-Naphthylamine chemistry MeSH
- Acrylic Resins chemistry MeSH
- Aniline Compounds chemistry MeSH
- Electrons * MeSH
- Catalysis MeSH
- Hydrogen-Ion Concentration MeSH
- Copper chemistry MeSH
- Equipment Reuse MeSH
- Piperazines chemistry MeSH
- Pyridinium Compounds chemical synthesis MeSH
- Green Chemistry Technology MeSH
- Publication type
- Journal Article MeSH
Based on the kinetics of interaction between a receptor and G-protein, a myriad of possibilities may result. Two extreme cases are represented by: 1/Collision coupling, where an agonist binds to the free receptor and then the agonist-receptor complex "collides" with the free G-protein. 2/Pre-coupling, where stable receptor/G-protein complexes exist in the absence of agonist. Pre-coupling plays an important role in the kinetics of signal transduction. Odd-numbered muscarinic acetylcholine receptors preferentially couple to G(q/11), while even-numbered receptors prefer coupling to G(i/o). We analyzed the coupling status of the various subtypes of muscarinic receptors with preferential and non-preferential G-proteins. The magnitude of receptor-G-protein coupling was determined by the proportion of receptors existing in the agonist high-affinity binding conformation. Antibodies directed against the C-terminus of the α-subunits of the individual G-proteins were used to interfere with receptor-G-protein coupling. Effects of mutations and expression level on receptor-G-protein coupling were also investigated. Tested agonists displayed biphasic competition curves with the antagonist [(3)H]-N-methylscopolamine. Antibodies directed against the C-terminus of the α-subunits of the preferential G-protein decreased the proportion of high-affinity sites, and mutations at the receptor-G-protein interface abolished agonist high-affinity binding. In contrast, mutations that prevent receptor activation had no effect. Expression level of preferential G-proteins had no effect on pre-coupling to non-preferential G-proteins. Our data show that all subtypes of muscarinic receptors pre-couple with their preferential classes of G-proteins, but only M(1) and M(3) receptors also pre-couple with non-preferential G(i/o) G-proteins. Pre-coupling is not dependent on agonist efficacy nor on receptor activation. The ultimate mode of coupling is therefore dictated by a combination of the receptor subtype and the class of G-protein.
- MeSH
- CHO Cells MeSH
- Cricetulus MeSH
- Guanosine 5'-O-(3-Thiotriphosphate) metabolism MeSH
- Carbachol metabolism MeSH
- Kinetics MeSH
- Binding, Competitive MeSH
- Cricetinae MeSH
- Humans MeSH
- Mutation MeSH
- N-Methylscopolamine metabolism MeSH
- GTP-Binding Proteins metabolism MeSH
- Receptors, Muscarinic genetics metabolism MeSH
- Animals MeSH
- Check Tag
- Cricetinae MeSH
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, N.I.H., Extramural MeSH
The catalytic versatility of cytochrome P450 monooxygenases is remarkable. Here, we present mechanistic and structural characterizations of TleB from Streptomyces blastmyceticus and its homolog HinD from Streptoalloteichus hindustanus, which catalyze unusual intramolecular C-N bond formation to generate indolactam V from the dipeptide N-methylvalyl-tryptophanol. In vitro analyses demonstrated that both P450s exhibit promiscuous substrate specificity, and modification of the N13-methyl group resulted in the formation of indole-fused 6/5/6 tricyclic products. Furthermore, X-ray crystal structures in complex with substrates and structure-based mutagenesis revealed the intimate structural details of the enzyme reactions. We propose that the generation of a diradical species is critical for the indolactam formation, and that the intramolecular C(sp2)-H amination is initiated by the abstraction of the N1 indole hydrogen. After indole radical repositioning and subsequent removal of the N13 hydrogen, the coupling of the properly-folded diradical leads to the formation of the C4-N13 bond of indolactam.
Gap junction connexin channels are important determinants of myocardial conduction and synchronization that is crucial for coordinated heart function. One of the main risk factors for cardiovascular events that results in heart attack, congestive heart failure, stroke as well as sudden arrhythmic death is hypertension. Mislocalization and/or dysfunction of specific connexin-43 channels due to hypertension-induced myocardial remodeling have been implicated in the occurrence of life-threatening arrhythmias and heart failure in both, humans as well as experimental animals. Recent studies suggest that down-regulation of myocardial connexin-43, its abnormal distribution and/or phosphorylation might be implicated in this process. On the other hand, treatment of hypertensive animals with cardioprotective drugs (e.g. statins) or supplementation with non-pharmacological compounds, such as melatonin, omega-3 fatty acids and red palm oil protects from lethal arrhythmias. The antiarrhythmic effects are attributed to the attenuation of myocardial connexin-43 abnormalities associated with preservation of myocardial architecture and improvement of cardiac conduction. Findings uncover novel mechanisms of cardioprotective (antihypertensive and antiarrhythmic) effects of compounds that are used in clinical settings. Well-designed trials are needed to explore the antiarrhythmic potential of these compounds in patients suffering from hypertension.
- MeSH
- Anti-Arrhythmia Agents pharmacology therapeutic use MeSH
- Antioxidants pharmacology therapeutic use MeSH
- Hypertension drug therapy metabolism pathology MeSH
- Connexin 43 metabolism MeSH
- Humans MeSH
- Melatonin pharmacology therapeutic use MeSH
- Gap Junctions ultrastructure MeSH
- Myocardium ultrastructure MeSH
- Plant Oils pharmacology therapeutic use MeSH
- Fatty Acids, Omega-3 pharmacology therapeutic use MeSH
- Heart drug effects MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Review MeSH
We aimed to explore whether specific high-sucrose intake in older female rats affects myocardial electrical coupling protein, connexin-43 (Cx43), protein kinase C (PKC) signaling, miR-1 and miR-30a expression, and susceptibility of the heart to malignant arrhythmias. Possible benefit of the supplementation with melatonin (40 μg/ml/day) and omega-3 polyunsaturated fatty acids (Omacor, 25 g/kg of rat chow) was examined as well. Results have shown that 8 weeks lasting intake of 30% sucrose solution increased serum cholesterol, triglycerides, body weight, heart weight, and retroperitoneal adipose tissues. It was accompanied by downregulation of cardiac Cx43 and PKCε signaling along with an upregulation of myocardial PKCδ and miR-30a rendering the heart prone to ventricular arrhythmias. There was a clear benefit of melatonin or omega-3 PUFA supplementation due to their antiarrhythmic effects associated with the attenuation of myocardial Cx43, PKC, and miR-30a abnormalities as well as adiposity. The potential impact of these findings may be considerable, and suggests that high-sucrose intake impairs myocardial signaling mediated by Cx43 and PKC contributing to increased susceptibility of the older obese female rat hearts to malignant arrhythmias.
- MeSH
- Anti-Arrhythmia Agents metabolism pharmacology MeSH
- Connexin 43 metabolism MeSH
- Dietary Sucrose adverse effects MeSH
- Rats MeSH
- Melatonin metabolism pharmacology MeSH
- MicroRNAs metabolism MeSH
- Myocardium metabolism MeSH
- Obesity chemically induced complications drug therapy metabolism MeSH
- Fatty Acids, Omega-3 metabolism pharmacology MeSH
- Rats, Wistar MeSH
- Protein Kinase C-delta metabolism MeSH
- Protein Kinase C-epsilon metabolism MeSH
- Signal Transduction drug effects MeSH
- Heart drug effects MeSH
- Arrhythmias, Cardiac etiology MeSH
- Animals MeSH
- Check Tag
- Rats MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
The mechanism of oxidative coupling of two naphthol molecules to form binaphthol catalyzed by Cu(OH)ClTMEDA (TMEDA=N,N,N',N'-tetramethylethylenediamine) was approached by means of a gas-phase model system. Concise evidence is provided that the coupling reaction proceeds in clusters with two Cu(II) centers, whereby the intermediacy of free naphthoxy radicals in the coupling step is avoided. In the absence of TMEDA, the cluster is bound via a bridging counterion and the coupling reaction is followed by cluster cleavage. The coordination of one or two TMEDA molecules to the reactive complex results in more efficient coupling of naphthol molecules, and moreover, the binuclear cluster is also conserved after the reaction is completed. The effect of TMEDA is twofold: First, it supports clustering of copper and, second, as a ligand bound to a copper center in the reactive complex, it weakens the bond between copper and the naphtholato ligand such that the naphtholato unit is more prone to undergo C--C coupling. Furthermore, a pronounced counterion effect is found that correlates well with condensed-phase data: weakly bridging counterions (e.g., NO3(-)) yield less stable dicopper clusters and the coupling reaction hardly occurs, whereas better bridging counterions (e.g., Cl(-) or Br(-)) provide more stable clusters that make the coupling reaction more efficient.
The hypodactylous (hd) locus impairs limb development and spermatogenesis, leading to male infertility in rats. We show that the hd mutation is caused by an insertion of an endogenous retrovirus into intron 10 of the Cntrob gene. The retroviral insertion in hd mutant rats disrupts the normal splicing of Cntrob transcripts and results in the expression of a truncated protein. During the final phase of spermiogenesis, centrobin localizes to the manchette, centrosome, and the marginal ring of the spermatid acroplaxome, where it interacts with keratin 5-containing intermediate filaments. Mutant spermatids show a defective acroplaxome marginal ring and separation of the centrosome from its normal attachment site of the nucleus. This separation correlates with a disruption of head-tail coupling apparatus, leading to spermatid decapitation during the final step of spermiogenesis and the absence of sperm in the epididymis. Cntrob may represent a novel candidate gene for presently unexplained hereditary forms of teratozoospermia and the "easily decapitated sperm syndrome" in humans.
- MeSH
- Sperm Tail metabolism MeSH
- Blotting, Far-Western MeSH
- Centrosome metabolism MeSH
- Microscopy, Electron MeSH
- Endogenous Retroviruses genetics MeSH
- Epididymis metabolism MeSH
- Fluorescent Antibody Technique MeSH
- Sperm Head metabolism MeSH
- Genes, Homeobox genetics MeSH
- Homeodomain Proteins metabolism MeSH
- Introns genetics MeSH
- Keratin-5 genetics metabolism MeSH
- Rats MeSH
- Mutation genetics MeSH
- Infertility, Male genetics metabolism MeSH
- Reverse Transcriptase Polymerase Chain Reaction MeSH
- Cell Cycle Proteins physiology MeSH
- Spermatids metabolism MeSH
- Spermatogenesis genetics MeSH
- Protein Transport genetics MeSH
- Animals MeSH
- Check Tag
- Rats MeSH
- Male MeSH
- Animals MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
Sleep manifests itself by the spontaneous emergence of characteristic oscillatory rhythms, which often time-lock and are implicated in memory formation. Here, we analyze a neural mass model of the thalamocortical loop in which the cortical node can generate slow oscillations (approximately 1 Hz) while its thalamic component can generate fast sleep spindles of σ-band activity (12-15 Hz). We study the dynamics for different coupling strengths between the thalamic and cortical nodes, for different conductance values of the thalamic node's potassium leak and hyperpolarization-activated cation-nonselective currents, and for different parameter regimes of the cortical node. The latter are listed as follows: (1) a low activity (DOWN) state with noise-induced, transient excursions into a high activity (UP) state, (2) an adaptation induced slow oscillation limit cycle with alternating UP and DOWN states, and (3) a high activity (UP) state with noise-induced, transient excursions into the low activity (DOWN) state. During UP states, thalamic spindling is abolished or reduced. During DOWN states, the thalamic node generates sleep spindles, which in turn can cause DOWN to UP transitions in the cortical node. Consequently, this leads to spindle-induced UP state transitions in parameter regime (1), thalamic spindles induced in some but not all DOWN states in regime (2), and thalamic spindles following UP to DOWN transitions in regime (3). The spindle-induced σ-band activity in the cortical node, however, is typically the strongest during the UP state, which follows a DOWN state "window of opportunity" for spindling. When the cortical node is parametrized in regime (3), the model well explains the interactions between slow oscillations and sleep spindles observed experimentally during Non-Rapid Eye Movement sleep. The model is computationally efficient and can be integrated into large-scale modeling frameworks to study spatial aspects like sleep wave propagation.
- Publication type
- Journal Article MeSH
- MeSH
- Adenosine-5'-(N-ethylcarboxamide) MeSH
- Antidepressive Agents, Second-Generation pharmacology MeSH
- Apoptosis drug effects MeSH
- Cytochrome P-450 CYP2D6 MeSH
- Enzyme-Linked Immunosorbent Assay MeSH
- Fluoxetine * pharmacology MeSH
- Type C Phospholipases drug effects MeSH
- Glioma MeSH
- Cytochrome P-450 CYP2D6 Inhibitors MeSH
- Culture Media MeSH
- Cells, Cultured MeSH
- Lymphocytes cytology MeSH
- Synaptic Transmission * drug effects MeSH
- GTP-Binding Protein alpha Subunits, Gq-G11 MeSH
- GTP-Binding Proteins * drug effects MeSH
- Selective Serotonin Reuptake Inhibitors pharmacology MeSH
- Signal Transduction MeSH
- In Vitro Techniques MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
