R7-binding protein targets the G protein β5/R7-regulator of G protein signaling complex to lipid rafts in neuronal cells and brain

Background  

Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain.     

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Decomposition of dichlorodifluoromethane in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixtures involving carbon, chlorine and fluorine in presence of argon (which is assumed to be the main plasma gas) and/or in addition of hydrogen and calcium together with hydrogen. The calculations were carried out for the temperature range between 500 and 6000 K and for the total pressure of the system of 1 bar. Use is made of the fact that a thermal plasma is a plasma in (local) thermal equilibrium, which makes possible the theoretical determination of its equilibrium composition at definite temperature by employing Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state. The results of calculations show that toxic molecules and radicals can be, under convenient conditions (appropriate temperature and amount of added substances), converted into stable non-toxic species like CaF₂ and CaCl₂.     

Polymerization-induced phase separation in polyether-sulfone modified epoxy resin systems: effect of curing reaction mechanism

Polyethersulfone (PES)-modified epoxy systems with stepwise reaction were studied throughout the entire curing process by using optical microscopes, time-resolved light scattering (TRLS), and a rheolometry instrument compared with that of chainwise polymerization. The results suggested that the phase separation process is mainly controlled by the diffusion of epoxy oligomers for stepwise mechanism system and by that of epoxy monomers for chainwise mechanism system. In case of high PES content (SPES-20%) light-scattering results showed a viscoelastic phase separation and the characteristic relaxation time of phase separation can be described well by the WLF equation. However, in the case of low PES content (SPES-14%) secondary phase separation phenomenon was observed by Optical Microscope and further demonstrated by rheological study.     

Electron collisions with trifluorides: BF3 and PF3 molecules

Absolute total cross sections (TCSs) for electron scattering from boron trifluoride (BF(3)) and phosphorus trifluoride (PF(3)) molecules have been measured using a linear transmission method. The electron energy ranges from 0.6 to 370 eV for BF(3) and from 0.5 to 370 eV for PF(3). The TCS energy dependence for BF(3) exhibits two very pronounced enhancements: resonantlike narrow feature located near 3.6 eV with the maximum value of 19.2 x 10(-20) m(2), and intermediate energy very broad enhancement with two humps, one centered around 21 eV (18.8 x 10(-20) m(2) in the maximum) and the other near 45 eV (19.5 x 10(-20) m(2)). For PF(3) the TCS has quite different low-energy dependence: at 0.5 eV it has a high value of 70 x 10(-20) m(2) and decreases steeply towards higher energies. Beyond the minimum near 5.5 eV, the TCS reveals two distinct humps: the resonant one centered near 11 eV with the peak value of 32.9 x 10(-20) m(2) and the second one much broader around 35 eV (27.9 x 10(-20) m(2)). The present TCSs for trifluorides are compared to each other as well as to previous TCS data for selected perfluorides and to results for their perhydrided counterparts. The differences and similarities in the shape and magnitude of TCSs are pointed out.     

A DFT study of pyramidalized alkenes: 7-oxasesquinorbornenes and 7,7′-dioxasesquinorbornenes

  DFT calculations of 7′–oxasesquinorbornenes and 7,7′-dioxasesquinorbornenes using the B3LYP/6–31G* method are reported. All the investigated structures (syn- and anti- derivatives) showed significant non-planarity of the central double bond, with the exception of those anti-derivatives possessing symmetrical structures. The influence of the replacement of the methylene groups at position 7- of the norbornene fragment with oxygen and the introduction of second and third (peripheral) double bonds and benzene rings on the molecular and electronic structures of these molecules have also been investigated. Received: 11 November 2002 / Accepted: 6 June 2002 / Published online: 29 April 2003     

Synthesis of 2•,3•-Dideoxy-3•-<Emphasis Type="Italic">C</Emphasis>-hydroxymethylcytidine Phosphonomethyl Derivatives

Phosphonomethyl substituted 2?,3?-Dideoxy-3?-C-hydroxymethylcytidines have been synthesized and evaluated for their anti HIV-1 activities. The sugar moiety was synthesized starting from (S)-5-hydroxymethylfuran-2-(5H)-one using photocatalyzed addition of methanol. Reduction of the lactone, condensation with silylated 4-methoxy-2(1H)pyrimidinone, followed by phosphonomethylation and deprotection gave the title compounds. The compounds were tested for inhibition of HIV-1 activity but did not show any significant antiviral activity.     

Synthesis,crystal structure and luminescent property of a novel H<Subscript>2</Subscript>O-bridged cobalt(II) polymer with one-dimensional chain structure

The coordination compound [Co(C₁₀H₇COO)₂(H₂O)₃]_2n · 4nH₂O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions. The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can be assigned to the intraligand electronic transfer.     

Initial anticrossing between Stark manifold <Emphasis Type="Italic">n</Emphasis> and <Emphasis Type="Italic">n</Emphasis>+1 in Na

We present the theoretical results for the positions and widths of the initial anticrossing between Stark manifold n and n + 1 in sodium, obtained by using the method of diagonalization in which zero-field wave functions are chosen from a kind of atomic potential model. These results can provide the quantitative information for understanding the microwave ionization process, whose rate-limiting step is probably the n to n + 1 transition performed at the first crossing between the outermost states of these two manifolds.     

Symmetry numbers and chemical reaction rates

This article shows how to evaluate rotational symmetry numbers for different molecular configurations and how to apply them to transition state theory. In general, the symmetry number is given by the ratio of the reactant and transition state rotational symmetry numbers. However, special care is advised in the evaluation of symmetry numbers in the following situations: (i) if the reaction is symmetric, (ii) if reactants and/or transition states are chiral, (iii) if the reaction has multiple conformers for reactants and/or transition states and, (iv) if there is an internal rotation of part of the molecular system. All these four situations are treated systematically and analyzed in detail in the present article. We also include a large number of examples to clarify some complicated situations, and in the last section we discuss an example involving an achiral diasteroisomer.     

Calorimetric titration experiment modelled by equilibrium of 2:1 and 1:1 complexes

The analysis of the calorimetric continuous titration experiment is presented. The proposed method is basing on the collection of larger number of experimental data points than could be obtained from the classical isothermal titration calorimetry experiment. After the deconvolution procedure resulting in the correction for the calorimeter time response the pure power effect signal could be obtained. The collected data enable the detailed analysis of the closely populated 2:1 and 1:1 weak complexes.