Genes involved in <Emphasis Type="Italic">Drosophila</Emphasis>glutamate receptor expression and localization

Background  

A clear picture of the mechanisms controlling glutamate receptor expression, localization, and stability remains elusive, possibly due to an incomplete understanding of the proteins involved. We screened transposon mutants generated by the ongoing Drosophila Gene Disruption Project in an effort to identify the different types of genes required for glutamate receptor cluster development.     

Rhenium ethoxy- and hydroxycarbene complexes with thiophene substituents

Reaction of mono- and dilithiated thiophene (a), bithiophene (b) and 2,5-dibromothiophene (c) with [Re(2)(CO)(10)] afforded, after subsequent alkylation with triethyloxonium tetrafluoroborate, tetra- and binuclear Fischer carbene complexes, [Re(2)(CO)(9){C(OEt){C(4)H(2)S}(n)X}], n = 1, X = H (1a); n = 2, X = H (1b); n = 1, X = Br (1c); n = 1, X = C(OEt)Re(2)(CO)(9), (2a); n = 2, X = C(OEt)Re(2)(CO)(9) (2b), as major products. The dirhenium acylate intermediates from this reaction not only gave the expected novel ethoxycarbene complexes with alkylation but after rhenium-rhenium bond breaking afforded a number of minor products. The (1)H NMR spectrum of the crude reaction mixture revealed the formation of four metal hydride complexes and aldehydes. Protonation with HBF(4) instead of alkylation with Et(3)OBF(4) significantly increased the yields of the hydride complexes, which enabled the positive identification of three of these complexes. In addition to the known compounds [Re(CO)(5)H] and [Re(3)(CO)(14)H] (3), a unique complex displaying a hydroxycarbene fragment connected to an acyl fragment via an O-H···O hydrogen bond and a Re···H···Re bond linking the two Re centers, [(μ-H){Re(CO)(4)C(OH){C(4)H(2)S}(n)H}{Re(CO)(4)C(O){C(4)H(2)S}(n)H}], n = 1 (4a) or n = 2 (4b), were isolated. The formation of thiophene aldehydes, H{C(O)}(m){C(4)H(2)S}(n)C(O)H (m = 0 or 1 and n = 1 or 2), were observed and the novel monocarbene complexes with terminal aldehyde groups, [Re(2)(CO)(9){C(OEt){C(4)H(2)S}(n)C(O)H}], n = 1 (5a) and n = 2 (5b) could be isolated. A higher yield of 5b was obtained after stirring crystals of 2b in wet THF. The crystal structures of 1a, 2a, 4a and 5b are reported.     

Ultrathin layer chromatography on nanostructured thin films

Ultrathin layer chromatography (UTLC) is a relatively new variant of thin layer chromatography, with a 10mum thick monolithic silica sorbent layer that gives faster separations with lower limits of detection and reduced analyte and solvent volumes. We have produced UTLC plates with controllable nanostructure and thickness, and show that the layer separation characteristics depends on the film nanostructure. We also show that layers made with in-plane anisotropic nanostructures will exhibit a decoupling effect, where the analyte spots do not develop in the same direction as the solvent front movement. The added layer morphology and material selection adds a degree of freedom to UTLC, and may have applications in multi-dimensional TLC.     

Giant Hysteretic Sorption of CO2: In Situ Crystallographic Visualization of Guest Binding within a Breathing Framework at 298 K

A dynamic Zn^II‐MOF has been shown to exhibit extreme breathing behavior under gas pressure. The very narrow pore form of the activated framework opens up in the presence of carbon dioxide, thus making it a suitable material for CO₂ capture. Sorption of CO₂ at 298 K and relatively high pressure clearly shows a two‐step isotherm with giant hysteresis for the second step. In‐situ single‐crystal diffraction analysis was carried out under CO₂ gas pressure at 298 K using an environmental gas cell in order to visualize the interaction between CO₂ and the host framework. The results are well supported by pressure‐gradient differential scanning calorimetry (P‐DSC) and variable‐pressure powder X‐ray analysis. Theoretical calculations have been carried out in order to further back up the crystallographic data.     

Axial and equatorial carbene ligands of dimanganese and dirhenium monocarbene complexes: Synthesis, characterisation and structural studies

The binuclear alkoxycarbene complexes [M₂(CO)₉{C(OEt)C₄H₃Y}] (M = Mn, Y = S(1), O(2); Re, Y = S(3), O(4)) were synthesised and characterised, giving axial carbene ligands for the dimanganese complexes, and equatorial carbene ligands for the dirhenium complexes. Aminolysis of these complexes with ammonia and n-propylamine yielded complexes [M₂(CO)₉{C(NHR)C₄H₃Y}] (R = H, M = Mn, Y = S(5), O(6); Re, Y = S(7), O(8); R = propyl, M = Mn, Y = S(9), O(10); Re, Y = S(11), O(12)). For the smaller NH₂-substituted carbene ligands, the X-ray structures determined showed equatorial carbene ligands for both dimanganese and dirhenium complexes, while the NHPr-substituted carbene complexes retained the original configurations of the precursor alkoxy carbene complex, indicating that the steric effects of both the M(CO)₅-fragment and the carbene ligand substituent can affect the coordination site of the carbene ligands of Group VII transition metal complexes in the solid state.     

Strict inequality for critical values of Potts models and random-cluster processes

We prove that the critical value _c of a ferromagnetic Potts model is astrictly decreasing function of the strengths of interaction of the process. This is achieved in the (more) general context of the random-cluster representation of Fortuin and Kasteleyn, by deriving and utilizing a formula which generalizes the technique known in percolation theory as Russo's formula. As a byproduct of the method, we present a general argument for showing that, at any given point on the critical surface of a multiparameter process, the values of a certain critical exponent do not depend on the direction of approach of that point. Our results apply to all random-cluster processes satisfying the FKG inequality.G.R.G. acknowledges support from Cornell University, and also partial support by the U.S. Army Research Office through the Mathematical Sciences Institute of Cornell University. H.K. was supported in part by the N.S.F. through a grant to Cornell University     

The influence of silicon on the non-equilibrium surface segregation of carbon in an FeSi 6.3 at% single crystal

The non-equilibrium surface segregation of carbon to the (110) plane of an Fe-Si single crystal was investigated as a function of temperature using Auger electron spectroscopy. It was found that the segregation rates at high temperatures were lower than expected from an extrapolation of low temperature segregation rates. This discrepancy is explained in terms of an interaction between the carbon and silicon atoms on the surface.     

Multimetal Fischer carbene complexes of Group VI transition metals: synthesis, structure and substituent effect investigation

Fischer carbene complexes of tungsten with substituents containing up to two additional different transition metals, with all the metals in electronic contact with the carbene carbon atom, were synthesised and studied both in solution and in the solid state. For the complexes of the type [W(CO)(5){C(OR')R}], the substituents chosen were heteroaromatic 2-benzo[b]thienyl (2-BT), or 2-BT π-bonded to a chromium tricarbonyl fragment ([Cr(CO)(3)(2-η(6)-BT)]) or ferrocenyl (Fc) as the R-substituent, while the OR'-substituent was systematically varied between an ethoxy or a titanoxy group, to yield the complexes 1b (R' = Et, R = 2-BT), 2b (R' = Et, R = [Cr(CO)(3)(2-η(6)-BT)]), 3b (R' = TiCp(2)Cl, R = 21-BT), 4b (R' = TiCp(2)Cl, R = [Cr(CO)(3)(2-η(6)-BT)]), 5b (R' = Et, R = Fc) and 6b (R' = TiCp(2)Cl, R = Fc). The structural features and their relevance to bonding in the multimetal carbene compounds of both these tungsten and the analogous chromium complexes were investigated as they represent indicators of possible reactivity sites in multimetal carbene assemblies. The possibility of using DFT calculations to quantify the effect of metal-containing substituents on the carbene ligands was tested and correlated with experimental parameters by employing methods such as vibrational spectroscopy, molecular orbital analysis, and cyclic voltammetry.     

Matrix‐free laser desorption/ionization mass spectrometry using silicon glancing angle deposition (GLAD) films

Glancing angle deposition (GLAD) was used to fabricate nanostructured silicon (Si) thin films with highly controlled morphology for use in laser desorption/ionization mass spectrometry (DIOS‐MS). Peptides, drugs and metabolites in the mass range of 150–2500 Da were readily analyzed. The best performance was obtained with 500 nm thick films deposited at a deposition angle of 85°. Low background mass spectra and attomole detection limits were observed with DIOS‐MS for various peptides. Films used after three months of dry storage in ambient conditions produced mass spectra with negligible low‐mass noise following a 15 min UV‐ozone treatment. The performance of the Si GLAD films was as good as or better than that reported for electrochemically etched porous silicon and related materials, and was superior to matrix‐assisted laser desorption/ionization (MALDI)‐MS for analysis of mixtures of small molecules between 150–2500 Da in terms of background chemical noise, detection limits and spot‐to‐spot reproducibility. The spot‐to‐spot reproducibility of signal intensities (100 shots/spectrum) from 21 different Si GLAD film targets was ±13% relative standard deviation (RSD). The single shot‐to‐shot reproducibility of signals on a single target was ±19% RSD (n = 7), with no indication of sweet spots or mute spots. Copyright © 2010 John Wiley & Sons, Ltd.     

Redox Behaviour of Cymantrene Fischer Carbene Complexes in Designing Organometallic Multi‐tags

A series of Group 7 Fischer carbene complexes, [Cp(CO)₂Mn^I=C(OEt)Ar] (Cp=cyclopentadienyl, Ar=Th=thienyl ( 1 a ), Ar=Fu=furyl ( 2 a ), Ar=Fc=ferrocenyl ( 3 a )) and biscarbene complexes, [Cp(CO)₂Mn?C(OEt)?Ar′?(OEt)C?Mn(CO)₂Cp] (Ar′=Th′=2,5‐thienylene ( 1 b ), Ar′=Fu′=2,5‐furylene ( 2 b ), Ar′=Fc′=1,1′‐ferrocendiyl ( 3 b )) was synthesized and characterized. Chemical oxidation of [Cp(CO)₂Mn?C(OEt)Fc] ( 3 a ) and isolation of the oxidised species [3 a][PF₆] possessing a Mn^II centre proved possible below ?30 °C in dichloromethane solution. The ESR spectrum of the transiently stable radical cation, [3 a][PF₆] , confirmed the presence of a low‐spin Mn^II centre characterized by a rhombic g tensor (g_x=1.975, g_y=2.007 and g_z=2.130) in frozen dichloromethane at 77 K with ⁵⁵ Mn hyperfine coupling constants A₁, A₂ and A₃ of 115, 33 and 43 G, respectively. Electrochemical studies demonstrated the influence of the Ar substituent on the oxidation potential. All complexes showed that the redox potentials of carbene double bond reduction and Mn^I oxidation were dependent on the type of Ar group, but only 3 b showed resolved oxidations for the two Mn^I centres. Surprisingly, Mn^I oxidation occurs at lower potentials than ferrocenyl oxidation. Density functional theory (DFT) calculations were carried out to delineate the nature of the species involved in the oxidation and reduction processes and clearly confirm that oxidation of Mn^I is favoured over that of ferrocene.