Relative quantification of erythropoietin receptor-dependent phosphoproteins using in-gel 18O-labeling and tandem mass spectrometry

On examining different proteomics approaches for the investigation of structure-function relationships of erythropoietin (EPO) receptor signaling, it was found that two-dimensional gel electrophoresis/mass spectrometry procedures are clearly limited in their ability to detect low-expressed signaling proteins. Instead it was found that a strategy involving anti-phosphotyrosine immunoprecipitation, one-dimensional gel electrophoresis (1DE), and capillary liquid chromatography/tandem mass spectrometry (LC/MS/MS) provides the sensitivity required for identification of signaling proteins. In the present work the immunoprecipitation/1DE/LC/MS approach was combined with an in-gel 18O-labeling technique to analyze EPO receptor-dependent proteins. Identification and relative quantification of more than 180 EPO receptor-dependent proteins were achieved directly based on the in-gel 18O-labeling approach.     

Thermoanalytical study of acetylacetonate-modified titanium(IV) isopropoxide as a precursor for TiO<Subscript>2</Subscript> films

Thermal decomposition of dried TiO₂ gel, obtained by hydrolysing acetylacetonate-modified titanium(IV) isopropoxide, was monitored by simultaneous TG/DTA/EGA-FTIR measurements in dynamic air up to 900&deg;C. XRD and FTIR were employed to identify the solid reaction products. Thermal degradation of the TiO₂ gel consists of five distinct mass loss steps, the total mass loss being 43.8&percnt;. EGA by FTIR revealed the release of H₂O below 120&deg;C; followed by acetone, isopropyl acetate and 1-propanol around 200-300&deg;C, and finally CO and CO₂ up to 550&deg;C. Highly exothermic reaction at 410-550&deg;C is caused by the combustion of carbon residues. Crystalline TiO₂-anatase is formed around 500&deg;C and TiO₂-rutile close to 800&deg;C.     

Micropatterning of DNA-tagged vesicles

We present a novel concept for the creation of lipid vesicle microarrays based on a patterning approach termed Molecular Assembly Patterning by Lift-off (MAPL). A homogeneous MAPL-based single-stranded DNA microarray was converted into a vesicle array by the use of vesicles tagged with complementary DNAs, permitting sequence-specific coupling of vesicles to predefined surface regions through complementary DNA hybridization. In the multistep process utilized to fulfill this achievement, active spots consisting of PLL-g-PEGbiotin with a resistant PLL-g-PEG background, as provided by the MAPL process, was converted into a DNA array by addition of complexes of biotin-terminated DNA and NeutrAvidin. This was then followed by addition of POPC vesicles tagged with complementary cholesterol-terminated DNA, thus providing specific coupling of vesicles to the surface through complementary DNA hybridization. Quartz crystal microbalance with dissipation (QCM-D) and optical waveguide lightmode spectroscopy monitoring were used to optimize the multistep surface modification process. It was found that the amount of adsorbed biotinDNA-NeutrAvidin complexes decreases with increasing molar ratio of biotinDNA to NeutrAvidin and decreasing ionic strength of the buffer solution. Modeling of the QCM-D data showed that the shape of the immobilized vesicles depends on the amount of available anchoring groups between the vesicles and the surface. Fluorescent microscopy images confirmed the possibility to create well-defined patterns of DNA-tagged, fluorescently labeled vesicles in the micrometer range.     

Novel Methods of Synthesis of Dibenzo[3n]crown-n and Their Cation Binding Studied by Fluorescence Spectroscopy. Part V

The dibenzo[3n]crown-n were synthesised starting from bis[2-(o-hydroxyphenoxy)ethyl]ether obtained from bis[2-(o-formylphenoxy)ethyl]ether via Baeyer-Villiger oxidation in H₂O₂/CH₃COOH in a good yield. The cyclic condensation ofbis[2-(o-hydroxyphenoxy)ethyl]etherwith tri- and tetraethylene glycol bisdichlorides andthe bisditosylate of pentaethylene glycol in DMF/Me₂CO₃ afforded the large cyclic ethers of dibenzo[21]crown-7, dibenzo[24]crown-8 and dibenzo[27]crown-9. The structures were analysed with IR, ¹H NMR, ¹³C NMR and low-resolution mass spectroscopy methods. The Na⁺, K⁺, Rb⁺ and Cs⁺ cations' recognition of the molecules were conducted withsteady-state fluorescence spectroscopy. The 1:1 association constants, K_a, in acetonitrile were estimated. Dibenzo[21]crown-7 was the best both for K⁺ and Rb⁺ binding but showed too small an effect on Cs⁺. Dibenzo[24]crown-8 exhibited the binding power in the order of Rb⁺ > K⁺ > Na⁺ > Cs⁺. However, dibenzo[27]crown-9 displayed marked binding with only K⁺ but not with Rb⁺ or with Cs⁺ cations probably due to the heavy atom effect of fluorescence quenching.     

From a monomer to a protein-sized, doughnut-shaped coordination oligomer-the influence of side chains of C3-symmetric ligands in supramolecular chemistry

Herein we describe the importance of side chains in C3-symmetric ligands in supramolecular chemistry. The reaction of the new ligand tris(5-bromo-2-methoxybenzylidene)triaminoguanidinium chloride [H3Me3Br3L]Cl (1) with ZnCl2 results in the formation of the monomeric complex (Et3NH)2[(ZnCl2)3Me3Br3L] (2), in which the ligand remains in a conformation less favourable for the coordination of metal centres. The use of the related tris(5-bromo-2-hydroxybenzylidene)triaminoguanidinium chloride, [H6Br3L]Cl, under similar conditions, results in the formation of two different dimeric compounds (NH4)[{[Zn(NH3)]3Br3L}2{mu-(OH)}3]1/4MeOH (3) and [Zn{Zn2(OH2)3(NH3)Br3L}2] (4), depending on the solvent mixture used. The comparable reaction of the ligand tris(5-bromo-2-hydroxy-3-methoxybenzylidene)triaminoguanidinium chloride [H6(OMe)3Br3L]Cl (5), leads to the formation of a doughnut-shaped, protein-sized coordination oligomer (Et3NH)18[{Zn[Zn2Cl{(OMe)3Br3L}]2}6(mu-Cl)6(OH2)6]x CH3CN (6), which comprises six dimeric [Zn5{(OMe)3Br3L}2] units. Whereas 3 and 4 decompose in DMSO solution, 6 is surprisingly stable in the same solvent.     

Mixed systems of hydrophobically modified polyelectrolytes: controlling rheology by charge and hydrophobe stoichiometry and interaction strength

Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification, and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separately can give high viscosities and a gel-like behavior, a pronounced maximum in viscosity and storage modulus with the mixing ratio of the polyelectrolytes is observed; the maximum is located between the points of charge and hydrophobe stoichiometry and reflects a combination of hydrophobic and electrostatic association. Lowering the charge density of the anionic polymer leads to a strengthened association at first, but at lower charge densities there is a weakened association due to the onset of phase separation. The strength of the electrostatic interaction was modified by adding salt. Increased ionic strength can lead to phase separation and to increased or decreased viscosity depending on the polyelectrolyte mixing ratio.     

π-Olefin-iridium-komplexe : IV. Umsetzungen von chloro-dien-iridium-verbindungen mit lithiumorganylen

The complexes [(1,3-C₆H₈)₂IrR] and [(1,3-C₇H₁₀)₂IrR] (R = CH₃, C₆H₅) are obtained by reaction of the corresponding chloro compounds with RLi. Interaction of [Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene) with CH₃Li in the presence of 1,3-cyclohexadiene or isoprene yields [(COD)(1,3-C₆H₈IrCH₃] and [(COD)(C₅H₈IrCH₃], respectively. The products of the reaction of chlorodicyclodieneiridium with n-C₄H₉Li depend on the ring size of the cyclodiene ligands; with 1,3-cyclohexadiene [(1,3-C₆H₈)₂IrH] is formed while with 1,3-cycloheptadiene [(1,3-C₇H₁₀)(C₇H₉)Ir] is obtained together with [(1,3-C₇H₁₀)₃Ir₂(μ-H)₂]. Chemical and spectroscopic properties of the new compounds are discussed.     

Die Boride HfCo3B2 und ZrCo3B2 als ternärer CaCu5-Typ

The ternary bodides HfCo₃B₂ and ZrCo₃B₂ crystallize with the hexagonal D 2_d structure type, space group P 6/mmm,a=4.840,c=3.036Å,c/a=0.627 anda=4.863,c=3.043Å,c/a=0.625, respectively. The boron atoms are located inside a trigonal prism that is familiar from other metal-rich borides. The ternary CaCu₅ type has good space filling at a theoretical axial ratioc/a=0.75 and a theoretical radius ratio of 1.5 ∶ 1 ∶ 0.81.     

Synthesis of new fluorescent dyes in the benzoxazinone series: Aminobenzoxazinones with a rigidized structure

The structure of 7-aminobenzoxazinones was modified by enclosing their amino nitrogen atom in a julolidyl ring. This rigidization was expected to enhance the fluorescence performances in this series. Several fluorescent dyes and styryl derivatives were prepared and their spectral characteristics were investigated. Comparison with homologous benzoxazinones with a flexible amino group shows that rigidization does not improve the quantum yield and the photochemical stability, in contrast with the results reported for other classes of dyes, like coumarins or rhodamines.