Bildung Siliciumorganischer Verbindungen. LV. Die Konformeren des 1,3,5,7-Tetrasila-bicyclo[3,3,1]nonans und 2,4,6,8,9-Pentasila-bicyclo[3,3,1]nonans

Formation of Organosilicon Compounds. LV. Conformeres of the 1,3,5,7-Tetrasilabicyclo [3,3,1] nonane and 2,4,6,8,9-Pentasila-bicyclo [3,3,1] nonane Two types of carbosilanes with a bicyclo [3,3,1] nonane structure are reported, derivatives of 1,3,5,7-Tetrasila-bicyclo-[3,3,1] nonane (a) and of 2,4,6,8,9-Pentasila-bicyclo [3,3,1] nonane (b) with an inverse structure in respect to the Si- and C-atoms. By means of NMR-investigations the structure can be determined. Derivatives of (a) are present in the Si₄C₁₁H₂₈ with fully methylated Si-atoms, the 1,5 dichloro-1,3,5,7-tetrasila-bicyclo [3,3,1] nonane and Si₄Cl₆C₅H₁₀ with fully chlorinated Si-atoms with twofold boat conformation. In the derivatives of type (b) as Si₅H₁₀C₄H₆ with hydrogenated Si-atoms as well as in 9,9-dichloro-2,4,6,8,9-pentasila-bicyclo [3,3,1] nonane a change in conformation is observed, whereas a rigid chair conformation is found for both rings in the Si-chlorimated derivative Si₅Cl₁₀C₄H₁₀. A comparison of atom-resp. H? H distances in cyclohexane and 1,3,5-Trisilacyclohexane gives evidence that the boat conformation is more preferable for the 1,3,5-Trisilacyclohexane than for cyclohexane due to larger H? H-distances (caused by Si? C-distances).     

The Gas-Solid Interface the adsorption of nitrogen,argon, neopentane,sulfur dioxide,carbon dioxide and sulfur hexafluoride on rhombic sulfur

Physical adsorption of the title compounds on rhombic sulfur of 0.4 to 0.5 m²/g is reported. The isotherms are of type II for N₂, Ar and C₅H₁₂, of type III for SO₂ and CO₂, and linear for SF₆. There is no hysteresis. The method of Ross & Olivier shows that the surface is relatively heterogenous (γ 17). Isosteric heats of adsorption and c values of the B.E.T. equation are also reported.     

ANTIVIRAL ACTIVITY OF MEROCYANINE 540

Abstract Simultaneous exposure to the lipophilic dye merocyanine 540 (MC 540) and white light inactivates several enveloped viruses. The same treatment appears to have little or no effect on pluripotent hematopoietic stem cells, mature red cells, and mature leukocytes. At least some components of the clotting system are spared, too. The molecular basis of the virucidal effect of MC 540 and light is not yet completely understood. Based on what is known about the interactions of MC 540 with cells and artificial membranes, it seems likely that MC 540 binds to and damages the viral envelope. MC 540-mediated photosensitization may have implications for the sterilization of bone marrow and blood products, the preparation of vaccines, and selected areas of antiviral therapy.     

Stereochemistry of Polynuclear Cadmium(II)thioglycolates: Crystal Structure of [ICd8(SCH2CH2OH)12]3+ · 3I− · H2O

Crystals of the title compound are triclinic, a = 27.87 Å, b = 10.77 Å, c = 12.94 Å, α 73.1°, β 116.1°, γ 120.0°, space group P1 . The structure consists of octanuclear ions: Eight Cd(II) ions are found at the corners of a distorted cube, the center of the cube is occupied by an iodide, the twelve thioglycolate sulfur atoms bridge the twelve edges of the cube thereby forming a distorted icosahedron. Cadmium ions are either five or seven coordinate. The phase problem for this structure was solved using a combination of very high and very low E-values.     

Colorimetric uranium determination with arsenazo

A rapid and sensitive method is described for the quantitative colorimetric determination of uranium(Vl). Masking agents such as EDTA, tartaric acid or thioglycerol make possible the determination of uranium in the presence of many foreign metal ions. If thorium is present, a preliminary extraction of uranium as the diethyldithiocarbamate is required.     

Phosphorothioate Analogues of Nucleotides—Tools for the Investigation of Biochemical Processes

Nucleoside phosphorothioates are analogues of nucleotides with a wide range of applications. Thus, on the one hand, in many but not all cases they are more stable against hydrolysis than the unmodified nucleotides—a property which they share with other nucleotide analogues. On the other hand, however, they are good substrates for many, but not all reactions where the nucleotide or the phosphorothioate group is transferred to an acceptor other than H₂O. As a consequence, once incorporated into a system such as DNA, phosphorothioates cannot be easily removed. What makes these compounds unique to a certain extent is the chirality at the phosphorus center if two nonequivalent residues are linked to the phosphorothioate group. This opens the way for the use of these compounds to investigate stereochemical aspects of enzymatic reactions. In addition to these properties, there are those expected from exchange of an oxygen for a sulfur atom in a phosphate group, e.g. the increased affinity towards mercury derivatives and the large chemical shift of the ³¹P-NMR sinals. If one considers how many biologically interesting compounds contain phosphate groups, the considerable interest in these nucleotide analogues is not surprising.     

Competitive Complexation of Lanthanide Cations by Xylitol and Nitrate Anion in Aqueous Solution: A Microcalorimetric Investigation

The apparent equilibrium constants and enthalpies of complexation of Nd³⁺, Sm³⁺, Eu³⁺, and Gd³⁺ by xylitol in aqueous solutions containing NaNO₃ at an ionic strength of 2.0 mol-kg^–1 have been determined by microcalorimetry at 25°C. Since nitrate anion weakly complexes the lanthanide cations, these values are analyzed in terms of competition between xylitol and NO ₃ ^- The method leads to the apparent equilibrium constants and enthalpies of complexation of the lanthanide cations by NO ₃ ^- at this particular ionic strength. Despite the difficulties encountered in characterizing rather weak associations, the results are, whenever comparison is possible, in good agreement with those obtained by direct microcalorimetry. The advantage of this competition method is that it can be used when the enthalpic effects are too weak and insufficiently concentration dependent for direct microcalorimetric determination. In the present case, it allows us to thermodynamically characterize the formation of SmNO ₃ ²⁺ and EuNO ₃ ²⁺ , processes we have not been able to study directly.     

Concentration and determination of trace organic pollutants in water

Organic pollutants in water are isolated on a mini-sampler tube containing a macroporous resin. The sorbed pollutants are next thermally transferred to a second sorption tube and then to an analytical column where they are separated and determined by temperature-programmed gas chromatography. Excellent recoveries were obtained for tests in which model organic compounds of various classes were added to water. The water sample is much smaller than that required with previous analytical methods.     

Study of Langmuir and Langmuir-Blodgett films of odorant-binding protein/amphiphile for odorant biosensors

To make ultrathin films for the fabrication of artificial olfactory systems, odorant biosensors, we have investigated mixed Langmuir and Langmuir-Blodgett films of odorant-binding protein/amphiphile. Under optimized experimental conditions (phosphate buffer solution, pH 7.5, OBP-1F concentration of 4 mg L(-1), target pressure 35 mN m(-1)), the mixed monolayer at the air/water interface is very stable and has been efficiently transferred onto gold supports, which were previously functionalized by self-assembled monolayers (SAMs) with 1-octadecanethiol (ODT). Atomic force microscopy and electrochemical impedance spectroscopy were used to characterize mixed Langmuir-Blodgett (LB) films before and after contact with a specific odorant molecule, isoamyl acetate. AFM phase images show a higher contrast after contact with the odorant molecule due to the new structure of the OBP-1F/ODA LB film. Non-Faradaic electrochemical spectroscopy (EIS) is used to quantify the effect of the odorant based on the electrical properties of the OBP-1F/ODA LB film, as its resistance strongly decreases from 1.18 MOmega (before contact) to 25 kOmega (after contact).