Infrared and Raman Spectra,Conformational Stability,Ab Initio Calculations,and Vibrational Assignments for Cyclopropyldifluorosilane

The infrared (3200–30 cm^–1) spectra of gaseous and solid Cyclopropyldifluorosilane, c-C₃H₅SiF₂H, and the Raman spectra (3200–20 cm^–1) of the liquid with quantitative depolarization values and the solid have been recorded. Both the syn (cis) and skew (gauche) conformers have been identified in the fluid phases, but only the syn conformer remains in the solid. Variable temperature (–55 to –100°C) studies of the infrared spectra of the sample dissolved in liquid xenon have been carried out. From these data, the enthalpy difference has been determined to be 73 ± 10 cm^–1 (209 ± 29 cal mol^–1), with the syn conformer being the more stable rotamer, which is at variance with the predictions from ab initio calculations. A complete vibrational assignment is proposed for both conformers based on infared band contours, relative intensities, depolarization values, and group frequencies. The vibrational assignments are supported by normal coordinate calculations utilizing the force constants from ab initio MP2/6-31G* calculations. Utilizing the frequencies of the silicon–hydrogen sketch, the rm Si—H bond distances of 1.474 and 1.472 Å have been obtained for the syn and skew conformers, respectively. Complete equilibrium geometries have been determined for both rotamers by ab initio calculations employing the 6-31G* and 6-311 +G** basis sets at levels of restricted Hartree-Fock (RHF) and/or Moller–Plesset (MP) to second order. The potential energy terms for the conformer interconversion have been obtained from the MP2/6-31G* calculation. The results are discussed and compared to those obtained for some similar molecules.     

Comparative binding of antitumor drugs to DNA containing the telomere repeat sequence

Telomeres are the ends of the linear chromosomes of eukaryotes and consist of tandem GT-rich repeats in telomere sequence i.e. 500-3000 repeats of 5'-TTAGGG-3' in human somatic cells, which are shortened gradually with age. The G-rich overhang of telomere sequence can adopt different intramolecular fold-backs and tetra-stranded DNA structures, in vitro, which inhibit telomerase activity. In this report, DNA binding agents to telomere sequence were studied novel therapeutic possibility to destabilize telomeric DNA sequences. Oligonucleotides containing the guanine repeats in human telomere sequence were synthesized and used for screening potential antitumor drugs. Telomeric DNA sequence was characterized using spectral measurements and CD spectroscopy. CD spectrum indicated that the double-stranded telomeric DNA is in a right-handed conformation. Polyacrylamide gel electrophoresis was performed for binding behaviors of antitumor compounds with telomeric DNA sequence. Drugs interacted with DNA sequence caused changes in the electrophoretic mobility and band intensity of the gels. Depending on the binding mode of the anticancer drugs, telomeric DNA sequence was differently recognized and the efficiency of cleavage of DNA varies in the bleomycin-treated samples under different conditions. DNA cleavage occurred at about 1% by the increments of 1 micromM bleomycin-Fe(III). These results imply that the stability of human telomere sequence is important in conjunction with the cancer treatment and aging process.     

The 'hybrid cell': a new compensated infinity cell for larger radius ion excitation in Fourier transform ion cyclotron resonance mass spectrometry

A new 'hybrid' ion cyclotron resonance (ICR) trap is proposed and analyzed by computer simulations. The trap is basically a hybrid of a segmented end cap (Infinity) and capacitively coupled cylindrical cell, with additional electrodes placed at the center of each end cap. The new trap produces an on-axis electric field z-profile similar to that of the Infinity cell or capacitively coupled open cylindrical cell during ion excitation. Simion simulations demonstrate that, during detection, appropriate changes of the potentials applied to the two new sets of electrodes produce a radial electric field z-profile that more closely approaches that for an ideal axial three-dimensional quadrupolar potential at high post-excitation ICR orbital radius, for improved signal-to-noise ratio and resolving power, and minimal m/z-discrimination.     

Prevention of TNF-induced necrotic cell death by rottlerin through a Nox1 NADPH oxidase

Previous studies have demonstrated that rottlerin, a specific PKCdelta inhibitor, potentiates death receptor- mediated apoptosis through a cytochrome c-dependent or -independent pathway. However, its ability to regulate necrotic cell death, as well as the underlying mechanism, remains unknown. We found that in murine fibrosarcoma L929 cells, treatment with rottlerin protected the cells against TNF-induced necrosis, whereas it sensitized the cells to apoptosis induced by co-treatment with Hsp90 inhibitor geldanamycin and TNF, in a manner independent of its ability to inhibit PKC-delta. TNF treatment induced rapid accumulation of mitochondrial superoxide (O2-) through the Nox1 NADPH oxidase when cells undergo necrosis. Moreover, pretreatment with rottlerin failed to induce the GTP-bound form of small GTPase Rac1 by TNF treatment, and subsequently suppressed mitochondrial O2- production and poly(ADP-ribose) polymerase activation, thus inhibiting necrotic cell death. Therefore, our study suggests that Nox1 NADPH oxidase is a new molecular target for anti-necrotic activity of rottlerin upon death-receptor ligation.     

Electron kinetic effects on Raman backscatter in plasmas

We augment the usual three-wave cold-fluid equations governing Raman backscatter (RBS) with a new kinetic thermal correction, proportional to an average of particle kinetic energy weighted by the ponderomotive phase. From closed-form analysis within a homogeneous kinetic three-wave model and ponderomotively averaged kinetic simulations in a more realistic pulsed case, the magnitude of these new contributions is shown to be a measure of the dynamical detuning between the pump laser, seed laser, and Langmuir wave. Saturation of RBS is analyzed, and the role of trapped particles illuminated. Simple estimates show that a small fraction of trapped particles (approximately 6%) can significantly suppress backscatter. We discuss the best operating regime of the Raman plasma amplifier to reduce these deleterious kinetic effects.     

Inhomogeneous level splitting in Pr 2-x BixRu2O7

We report that Bi doping drives Pr 2-x BixRu2O7 from an antiferromagnetic insulator (x = 0) to a metallic paramagnet (x approximately 1) with a broad low T maximum in C/T. Neutron scattering reveals local low energy spin excitations (variant Planck's omega approximately 1 meV) with a spectrum that is unaffected by heating to k(B)T > variant Planck's omega. We show that a continuous distribution of splittings of the non-Kramers Pr3+ ground-state doublet such as might result from various types of lattice strain can account for all the data.     

Étude dans le système mercure solution acide des courbes I = f(E) relatives au dépôt et à la redissolution de traces de: Cu,Tl, Cd,Zn, Ni,Co, Fe

It is possible to redissolve in acid solution traces of Cu, Tl and Zu previously deposited on mercury without oxidising the mercury; the concentrations considered arcofthc order of 100y per ml of amalgam. Under the same conditions the redissolution of traces of Fe, Ni and Co can not be carried out without oxidation of the mercury.The constiuction in 1N H₂SO₄ medium of the curves I = f(E) for the Cu, Cd and Tl ions, the current I being negligible compared with the diffusion current, shows that. a. the variations in log I as a function of the potential E of the mercury or amalgam electrode are linear. b. the position of the curve log I — log a = f(E) is independent of the activity a of the element in solution or amalgam.Our experiments also show: 1° it is necessary to introduce a température coefficient for the coefficient relative to the overpotential of hydrogen on the mercury. 2° for cadmium, at weak current densities, a single electron is put into play in the case of deposition and in that of redissolving.     

Dosage gravimétrique rapide du béryllium dans les béryls

After attacking the beryl by fusing the powdered mineral with sodium peroxide and eliminating silica, beryllium is precipitated directly in the filtrate by mono-ammonium phosphate in the presence of complexon II or ethylene diamino-tetraacetic acid.Complexon II forms complexes and retains in the solution the other metals contained in beryl, but permits the quantitative precipitation of ammonium phosphate and beryllium which is calcined at 1000° and weighed out as beryllium pyrophosphate, Be2P2O7.     

Cinétique d'électrolyse de traces métalliques avec dégagement simultané d'hydrogène

The authors have determined, for analytical purposes, the influence of a certain number of factors affecting the kinetics of deposition of metallic traces on a platinum or mercury cathode when there is a simultaneous discharge of a large amount of hydrogen ions.The phenomenon of exaltation of the migration current of an ion in the presence of the simultaneous discharge of another chemical species allows an explanation of the parts played by the different factors considered.