Unexpected Coupling Research Articles

Chemistry of Unsaturated Group 6 Metal Complexes with Bridging Hydroxy and Methoxycarbyne Ligands. 6. C−E Bond Formation and C−O Bond Cleavage Processes in the Reactions of [Mo2(η5-C5H5)2(μ-COMe)(μ-PCy2)(μ-CO)] with Several p-Block Elements (E) and Their Hydride Derivatives

The unsaturated complex [Mo2Cp2(μ-COMe)(μ-PCy2)(μ-CO)] (1) reacts with several HERn molecules (HERn = HSPh, HPHPh, HSnPh3) in toluene at 263−288 K to give the corresponding derivatives [Mo2Cp2(μ-ERn)(μ-PCy2)(CO)2]. A related reaction takes place in toluene at 263 K with the diphosphite (EtO)2POP(OEt)2 to give a mixture of the diethoxyphosphide derivatives [Mo2Cp2(μ-PCy2){μ-P(OEt)2}(CO)2] and [Mo2Cp(η5-C5H4CH2Ph)(μ-PCy2){μ-P(OEt)2}(CO)2], the latter incorporating a benzyl group from the solvent, and with iodine (in dichloromethane at room temperature) to give first the iodide complex [Mo2Cp2(μ-I)(μ-PCy2)(CO)2] and then the triiodide derivative [Mo2Cp2(μ-I)I2(μ-PCy2)(CO)2]. In all of the above reactions, neat demethylation of the methoxycarbyne ligand takes place. In contrast, the silanes HSiPh3 and H2SiPh2 (unreactive toward 1 in refluxing toluene) react slowly under visible−UV irradiation at room temperature to give in good yields the novel complexes [Mo2Cp2{μ-C(2-C6H4SiPh2OMe)}(μ-PCy2)(μ-CO)] and [Mo2Cp2(μ-CSiPh2OMe)(μ-PCy2)(μ-CO)], having arylcarbyne and silylcarbyne ligands, respectively, the latter resulting from the overall elimination of H2 and insertion of Ph2SiC6H4 and SiPh2 fragments, respectively, into the strong C−OMe bond of the carbyne ligand. The reactions of 1 with elemental selenium and sulfur involve the incorporation of three to four chalcogen atoms to the dimetal center under mild conditions, to give respectively the carbene-seleniolate derivative [Mo2Cp2{μ-C(OMe)C(O)Se}(μ-PCy2)(μ-Se2)] and the O-methyldithiocarbonate [Mo2Cp2(μ-PCy2){μ-S2C(OMe)}(S)2], the latter derived from an unexpected coupling of two sulfur atoms to the carbyne ligand.

Ramanujan Dietary Complements: Quantitative Identification of Optimal Protein Couplings for Vegan and Vegetarian Diets

A balanced vegetarian or vegan diet requires eating not only enough protein, but also the correct relative proportions of amino acids. Traditional pairings of legumes and grains, or grains and milk provide an approximately balanced diet, however among specific foods there is significant variation in the relative amino acid proportions. To identify optimal protein complements, we have developed an analytical tool called Ramanujan. Using amino acid profiles provided by the USDA database, we use Ramanujan to identify single foods and two‐, and three‐component food couplings that yield an amino acid profile most similar to a standard protein source of raw egg white. The results identify both traditional and unexpected couplings, and in so doing provide a novel, data‐driven resource to balance amino acid consumption in vegetarian diets.

Pd-catalyzed cross-coupling of carboxylic acids with nitroethane via combination of decarboxylation and dehydrogenation

An unexpected coupling reaction of arene carboxylic acid with nitroethane via a combination of decarboxylation and dehydrogenation is described. The method provides exclusively (E)-beta-nitrostyrenes.

Promyelocytic leukemia protein specifically augments the activation of NFAT (136.11)

Abstract Promyelocytic leukemia (PML) protein is a tumor suppressor with complicated action mechanisms not yet fully understood. Nuclear factor of activated T cells (NFAT) is an important factor for T cell functions. In this study, we found that PML specifically enhanced the transcription activation of NFAT. In PML-null mouse embryonic fibroblasts, no transcription activity of NFAT could be detected. There was a selective requirement of PML isoform in NFAT activation: PML-I and PML-VI, but not PML-IV, increased NFAT transactivation. PML specifically promoted the expression of many, but not all, NFAT targeted genes, including TNF Ą, TRAIL and Cbl-b. A specific binding of PML to NFATc was found by GST pull down assay and immuno-precipitation. The interaction of PML with NFATc in vivo was further confirmed by ChIP and DNA affinity precipitation assay (DAPA) analysis. Knockdown of PML was associated with reduced nuclear presence of NFAT. The unexpected coupling of PML with NFAT reveals a novel mechanism underlying the diverse physiological functions of PML.

Density Functional Theory Calculation of Bonding and Charge Parameters for Molecular Dynamics Studies on [FeFe] Hydrogenases.

We have developed and tested molecular mechanics parameters for [FeS] clusters found in known [FeFe] hydrogenases. Bond stretching, angle bending, dihedral and improper torsion parameters for models of the oxidized and reduced catalytic H-cluster, [4Fe4S](+,2+)Cys4, [4Fe4S](+,2+)Cys3His, and [2Fe2S](+,2+)Cys4, were calculated solely from Kohn-Sham density functional theory and Natural Population Analysis. Circumsphere analysis of the cubane clusters in the energy-minimized structure of the full Clostridium pasteurianum hydrogenase I showed the resulting metallocluster structures to be similar to known cubane structures. All clusters were additionally stable in molecular dynamics simulations over the course of 1.0 ns in the fully oxidized and fully reduced enzyme models. Normal modes calculated by quasiharmonic analysis from the dynamics data show unexpected couplings among internal coordinate motions, which may reflect the effects of the protein structure on metallocluster dynamics.

Physiological integration of roots and shoots in plant defense strategies links above‐ and belowground herbivory

Roots play a critical, but largely unappreciated, role in aboveground anti-herbivore plant defense (e.g. resistance and tolerance) and root-leaf connections may therefore result in unexpected coupling between above- and belowground consumers. Using the tobacco (Nicotiana tabacum) system we highlight two examples of this phenomenon. First, the secondary metabolite nicotine is produced in roots, yet translocated aboveground for use as a foliar resistance trait. We demonstrate that nematode root herbivory interferes with foliar nicotine dynamics, resulting in positive effects on aboveground phytophagous insects. Notably, nematode-induced facilitation only occurred on nicotine-producing plants, and not on nicotine-deficient mutants. In the second case, we use stable isotope and invertase enzyme analyses to demonstrate that foliar herbivory elicits a putative tolerance response whereby aboveground nutritional reserves are allocated to roots, resulting in facilitation of phytoparasitic nematodes. Thus, plants integrate roots in resistance and tolerance mechanisms for leaf defense, and such root-leaf connections inherently link the dynamics of above- and belowground consumers.

Selective activation of NFAT by promyelocytic leukemia protein

Promyelocytic leukemia (PML) protein is a tumor suppressor with complicated action mechanisms not yet fully understood. In this study, we found that the nuclear factor of activated T cell (NFAT) is an unexpected partner of PML: PML specifically enhanced the transcription activation of NFAT. In PML-null mouse embryonic fibroblasts, no transcription activity of NFAT could be detected. There was a selective requirement of PML isoform in NFAT activation: PML-I and PML-VI, but not PML-IV, increased NFAT transactivation. PML specifically promoted the expression of many, but not all, NFAT-targeted genes. We found a specific binding of PML to NFATc. The interaction of PML with NFATc in vivo was further confirmed by chromatin immunoprecipitation and DNA affinity precipitation assay analysis. The unexpected coupling of PML with NFAT reveals a novel mechanism underlying the diverse physiological functions of PML.

Evolutionary coupling between the deleteriousness of gene mutations and the amount of non-coding sequences

The phenotypic effects of random mutations depend on both the architecture of the genome and the gene–trait relationships. Both levels thus play a key role in the mutational variability of the phenotype, and hence in the long-term evolutionary success of the lineage. Here, by simulating the evolution of organisms with flexible genomes, we show that the need for an appropriate phenotypic variability induces a relationship between the deleteriousness of gene mutations and the quantity of non-coding sequences maintained in the genome. The more deleterious the gene mutations, the shorter the intergenic sequences. Indeed, in a shorter genome, fewer genes are affected by rearrangements (duplications, deletions, inversions, translocations) at each replication, which compensates for the higher impact of each gene mutation. This spontaneous adjustment of genome structure allows the organisms to retain the same average fitness loss per replication, despite the higher impact of single gene mutations. These results show how evolution can generate unexpected couplings between distinct organization levels.

Polymorphism in an unexpected caesium complex of 5-hydroxyhydurilic acid

Vigorous reaction of barbituric acid with caesium hydroxide in water resulted in an unexpected coupling product, 5-hydroxyhydurilic acid, complexed to caesium, giving poly[[caesium-mu5-5-hydroxyhydurilato] hemihydrate], {[Cs(C8H5N4O7)].0.5H2O}n. This was obtained in two different polymorphic forms, depending on the method of crystal growth. Slow solvent evaporation yielded an orthorhombic polymorph, (I), which crystallized in the space group Pnab (non-standard setting of Pbcn), with the uncoordinated water molecule lying on a crystallographic twofold axis. The water molecule is sandwiched into cavities within the structure and is securely held in place by N-HO and O-HO hydrogen bonding. Polymorph (II) is monoclinic, although the unit-cell parameters are similar to those of polymorph (I), and it crystallizes in the space group C2/c, with the uncoordinated water molecule again lying on the twofold axis and secured by hydrogen bonding. The differences between the two polymorphs, both of which have nine-coordinate caesium and a similar first-shell environment of all structural components, are in the overall arrangement of the cations, anions and water molecules, and in the shape of the cavities, revealed by inspecting and comparing crystal-packing diagrams.

Simple Design Formula for Parallel Plate Mode Suppression by Ground Via-Holes in Multi-Layered Packages

In a multi-layered RF circuit, it is important to avoid unexpected coupling caused by a parallel plate mode excited between different ground layers. Ground via-holes that short-circuit different ground layers are used for suppressing this mode. Quantitative evaluation of relations between suppression effect and ground via-hole disposition is required for optimal design. In this paper, a simple design formula that describes the suppression ratio is derived by mode-matching technique. The results of comparison with an FEM simulation validate our proposed formula. It is shown that the technique is indispensable for designing optimal disposition of via-holes to minimize the area of the ground via-holes for desired performance.

Assessment of predictions of the response of the Hualien containment model during forced vibration tests

Blind predictions for the response of the 1/4-scale reinforced concrete Hualien (Taiwan) containment model during forced vibration tests are compared with the observed data. The predictions obtained by the CLASSI approach reflect the experimental conditions prior to and after backfill of the soil surrounding the embedded foundation. The experimental data show a strong and unexpected coupling between the response in the NS and EW directions which is not present in the results for the axisymmetric theoretical models. Also, significant differences can be seen between the experimental responses in the two orthogonal horizontal directions which minimize cross-axis coupling. Although these differences are not accounted for in the theoretical models, the discrepancies between predictions and observations are within the uncertainty of the structural and geotechnical data. The obtained differences between predictions and observations give an excellent measure of the prediction error that can be expected in this type of analysis from uncertainty in the data. A detailed assessment of the initial structural and geotechnical data based on extensive comparisons with the results of previous identification studies is also presented. Finally, comparisons between the observed response and calculations based on revised models for the structure and the soil show that current methods of analysis can account accurately for the observed response.

Unexpected Coupling of Cp and Two RNC Ligands at a {Mo2(μ-SMe)3} Nucleus

Reaction of the bis-isonitrile complex [Mo2Cp2(μ-SMe)3(t-BuNC)2](BF4) (1) with n-BuLi (in hexane) produced the dealkylated derivative [Mo2Cp2(μ-SMe)3(t-BuNC)(CN)] (2) in quantitative yield. However...

Unexpected coupling between an eta5-indenyl ligand and alkenyl-vinylidene fragments: synthesis of unprecedented (eta6-indene)ruthenium(II) metallacycles.

Vinylidene complexes [Ru[=C=C(H)CR1R2CH2C(Me)=CH2](eta5-C9H7)(PPh3)2][BF4] undergo an intramolecular coupling between the alkenyl-vinylidene fragment and the eta5-indenyl ligand to afford indene-metallacyclic compounds (6a,b) in which the resulting functionalised indene group is eta6-coordinated to the metal.

Novel Organophosphorus Cage Compound Produced by an Unexpected Oxidative Coupling of 1,2,4-Triphosphole: Crystal and Molecular Structures of Two Isomers of Formula P6C4Bu t4 CHSiMe3

Li(P3C2But2) reage com BrCH(SiMe3)2, via adicao oxidativa, formando um novo composto organofosforado de formula molecular P6C4But4 CHSiMe3 (1). O composto 1 foi caracterizado espectroscopicamente e sua estrutura molecular determinada atraves de difracao de raios X de monocristais. Juntamente com 1, foi caracterizado outro composto (2) com a mesma formula molecular, mas apresentando uma estrutura completamente saturada.

Role of Rpn11 metalloprotease in deubiquitination and degradation by the 26S proteasome.

The 26S proteasome mediates degradation of ubiquitin-conjugated proteins. Although ubiquitin is recycled from proteasome substrates, the molecular basis of deubiquitination at the proteasome and its relation to substrate degradation remain unknown. The Rpn11 subunit of the proteasome lid subcomplex contains a highly conserved Jab1/MPN domain-associated metalloisopeptidase (JAMM) motif-EX(n)HXHX(10)D. Mutation of the predicted active-site histidines to alanine (rpn11AXA) was lethal and stabilized ubiquitin pathway substrates in yeast. Rpn11(AXA) mutant proteasomes assembled normally but failed to either deubiquitinate or degrade ubiquitinated Sic1 in vitro. Our findings reveal an unexpected coupling between substrate deubiquitination and degradation and suggest a unifying rationale for the presence of the lid in eukaryotic proteasomes.

An Unexpected Coupling - Isomerization Sequence as an Entry to Novel Three-Component-Pyrazoline Syntheses This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. We thank Prof. Dr. H. Mayr for his generous support.

An Unexpected Coupling - Isomerization Sequence as an Entry to Novel Three-Component-Pyrazoline Syntheses This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. We thank Prof. Dr. H. Mayr for his generous support.

Glutamate-89 in subunit II of cytochrome bo3 from Escherichia coli is required for the function of the heme-copper oxidase.

Recent electrostatics calculations on the cytochrome c oxidase from Paracoccus denitrificans revealed an unexpected coupling between the redox state of the heme-copper center and the state of protonation of a glutamic acid (E78II) that is 25 A away in subunit II of the oxidase. Examination of more than 300 sequences of the homologous subunit in other heme-copper oxidases shows that this residue is virtually totally conserved and is in a cluster of very highly conserved residues at the "negative" end (bacterial cytoplasm or mitochondrial matrix) of the second transmembrane helix. The functional importance of several residues in this cluster (E89II, W93II, T94II, and P96II) was examined by site-directed mutagenesis of the corresponding region of the cytochrome bo(3) quinol oxidase from Escherichia coli (where E89II is the equivalent of residue E78II of the P. denitrificans oxidase). Substitution of E89II with either alanine or glutamine resulted in reducing the rate of turnover to about 43 or 10% of the wild-type value, respectively, whereas E89D has only about 60% of the activity of the control oxidase. The quinol oxidase activity of the W93V mutant is also reduced to about 30% of that of the wild-type oxidase. Spectroscopic studies with the purified E89A and E89Q mutants indicate no perturbation of the heme-copper center. The data suggest that E89II (E. coli numbering) is critical for the function of the heme copper oxidases. The proximity to K362 suggests that this glutamic acid residue may regulate proton entry or transit through the K-channel. This hypothesis is supported by the finding that the degree of oxidation of the low-spin heme b is greater in the steady state using hydrogen peroxide as an oxidant in place of dioxygen for the E89Q mutant. Thus, it appears that the inhibition resulting from the E89II mutation is due to a block in the reduction of the heme-copper binuclear center, expected for K-channel mutants.

1H, 13C and 19F NMR Studies of the Diels-Alder Adduct of p-Fluoranil with Phencyclone. II. Hindered Phenyl Rotations and Anisotropic Effects in a Model Compound for Drugs

The Diels-Alder adduct of phencyclone, compound 1, with p-fluoranil, compound 3, has been prepared in refluxing toluene. The adduct, compound 2, has been examined by 1H, 13C and 19F NMR spectroscopy at 300, 75 and 282 MHz, respectively. At ambient temperature, the unsubstituted bridgehead phenyl groups in adduct 2 are found to exhibit hindered rotation, resulting in slow exchange limit (SEL) 1H NMR spectra. Full aryl proton assignments are made based on 1D and 2D (COSY45) NMR. The 19F NMR (proton coupled) reveals one of the two 19F signals to be a triplet. This resonance collapses to a singlet in the proton decoupled 19F spectrum, implying an unexpected long range 1H-19F coupling. For the 13C NMR spectrum, tentative assignments are presented. Data for compound 2 as a model compound for drugs are discussed in terms of the hindered aryl rotation and evidence of magnetic anisotrppic effects.

AC loss measurements of the experiments on a single inner vertical coil (EXSIV) for the Large Helical Device

The AC losses of the Inner Vertical (IV) coil have been measured during the Experiments on a Single Inner Vertical coil (EXSIV). The IV coils are the smallest poloidal coils of the Large Helical Device (LHD) and their inner and outer diameters are 3.2 m and 4.2 m, respectively. The coil consists of 16 pancake coils wound with the cable-in-conduit conductors (CICC) whose strands are NbTi/Cu without any surface coating. The AC losses were measured with a calorimetric method during excitation tests and current shut-off tests. In addition to the usual inter-strand coupling losses with short time constants, unexpected coupling losses were observed due to the coupling current of a long time constant.

Unexpected Coupling Reaction of 9-Lithiobromomethylene-9H-fluorene with 6,6-Dicyclopropylfulvene

Unexpected Coupling Reaction of 9-Lithiobromomethylene-9H-fluorene with 6,6-Dicyclopropylfulvene