Publications

Unique reactions occurring at the interface between air and aqueous solutions are increasingly recognized to be of potential importance in atmospheric processes. Sulfur dioxide was one of the first species for which experimental evidence for the existence of a surface complex was obtained by several different groups, based on the kinetics of SO2 uptake into aqueous solutions, large decreases in surface tension and second harmonic generation spectroscopic studies. The uptake has been proposed to involve an uncharged surface complex which subsequently converts into ionic species. We report here the results of a search for an uncharged SO2 complex at or near the surface using attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR) at 298 K guided by ab initio calculations of a 1:1 SO2-H2O complex. No infrared absorption bands attributable to such a complex of SO2 were observed experimentally in the expected region, giving an upper bound of 4 x 10(14) SO2 cm(-2) to the concentration of neutral SO2 molecules weakly sorbed to the surface in equilibrium with similar to1 atm SO2(g). The implications for the nature of the surface species and previous observations are discussed.

OBJECTIVES: This study assessed the phenotypic variability of LQTS in carriers with the same and with different mutations in the LQT2 gene. BACKGROUND: Mutations of ion-channel genes are known to cause the long QT syndrome (LQTS), a disorder associated with distinctive genotypic-specific electrocardiographic patterns and variable clinical expression. METHODS: Clinical and electrocardiographic characteristics were assessed in five large LQTS families, each with a different mutation of the HERG gene (LQT2; n = 469, 69% genotyped, 102 carriers). One mutation was located on the N-terminus and the other four on the C-terminus of the HERG channel protein. RESULTS: The QTc duration and the frequency of cardiac events (syncope and LQTS-related cardiac arrest/death) were similar among carriers with the five HERG mutations. QTc was as variable in carriers of the same mutation as it was among carriers with different HERG mutations (P = 0.19). Qualitative assessment of the electrocardiograms revealed extensive intra-and interfamilial variability in T-wave morphology. Among carriers with multiple electrocardiograms extending over 2 to 7 years, variation in QTc over time was minimal. A strong association was found between QTc and the occurrence of cardiac events in carriers of all five mutations. CONCLUSIONS: The clinical expression of LQTS was equally variable in carriers from families with the same or different HERG mutations. These findings highlight the complexity of the clinical phenotype in this Mendelian dominant disorder and suggest that one or more modifier genes contribute to the variable expression of this syndrome.

The vibrational spectroscopy and the matrix-site geometries of several novel rare-gas compounds in the matrix environment were computed theoretically, and compared with experiment. Ab initio calculations are used in the fitting of analytical potential surfaces for the HRgY molecules and for the interactions between HRgY and the matrix atoms Rg. With these potentials, matrix-site geometries for the molecule in the solid are computed. Finally, the vibrational spectroscopy of HRgY in the Rg matrix is computed using the vibrational self-consistent field (VSCF) method. The VSCF includes anharmonic effects, that are essential in this case. The version of VSCF used here includes coupling between HRgY and the vibrations of the solid atoms. The vibrations of 72 matrix atoms are treated. The main results are: (1) The matrix shifts are considerably greater than typically found for neutral, strongly bond molecules, but are much smaller than discrepancies between theory and experiment. This can be attributed to the insufficient accuracy of the potentials used for the HRgY molecules. This calls for better future description of the electronic structure of HRgY. (2) The matrix shifts and splitting effects are interpreted by the calculations in terms of the site geometries involved. These effects are very different for HArF, HKrF than for HXeCl, HXeI. (3) The computed matrix-site splittings are in semiquantitative accord with experiment. This supports the interaction potentials used between HRgY and the matrix. The results provide insights on the effects of the matrix on the rare-gas molecules. (C) 2002 American Institute of Physics.

We show by computations that even low voltages can significantly modify the electronic states of a small compressed array of metallic quantum dots. This is because the voltage counteracts the effects of inherent disorder on the wave function. The low-lying excitations can be thermally probed. At lower voltages the array breaks into islands that are superexchange coupled. At higher voltages the response is ohmic, then it cuts out due to formation of a junction layer.

The in situ adsorption/desorption studies of 14C-labeled human IgG were performed at the polyethylene (PE)/aq. soln. interface. The results reveal that the adsorbed protein mols. were predominantly packed in the end-on orientation. Desorption expts. showed that upon rinsing with buffer only minute fractions of adsorbed IgG could be removed from the PE surface. Both the competitive and the sequential adsorption measurements from the binary mixts. of hydrophobic IgG modified by attachment of 19 caprylic chains (19C8-IgG) and [14C]IgG confirm that native IgG strongly adhered to the PE films. The specific recognition ability of adsorbed human IgG layers was studied by using specific (goat anti-human) IgG and nonspecific (goat anti-rabbit) IgG. It was shown that the prevailing effect of the interaction of [14C]IgG adsorbed onto PE with the specific antibody was the increase in the surface radioactivity, which was attributed to the formation of a more densely packed layer of IgG mols. at the PE surface. It was also demonstrated that, whereas the specific antibody preadsorbed onto PE films retained the recognition ability relative to human IgG, its hydrophobic modification resulted in a substantial decrease in this ability. (c) 2001 Academic Press. [on SciFinder(R)]

Adsorption onto silica of native human IgG and its hydrophobized forms prepd. by covalent attachment of 11, 25, and 52 C8 alkyl chains was studied. All hydrophobized IgGs spontaneously form micelle-like aggregates (nanoclusters) in aq. solns. with a mean diam. of 40 nm. Adsorption isotherms are of a high affinity type. The plateau surface concn. of the isotherms depends on the degree of the protein modification, increasing for 11C8-IgG and 25C8-IgG and decreasing for 52C8-IgG as compared with the native protein. The isothermal enthalpies of adsorption for the native and modified IgGs at all degrees of silica surface coverage were endothermic, i.e., the adsorption process is entropically driven. For the native IgG, the adsorption isotherm is apparently reversible, while the isotherms for the modified forms display distinct hysteresis. The biol. (immunol.) activity of the desorbed mols. was evaluated, and it was found that all forms of IgG which were desorbed from silica display reduced ability to react with a specific antibody, goat anti-human IgG, compared to the corresponding forms before adsorption. The immunoassay on desorbed IgGs indicated that hydrophobic modification of the mol. reduced structural alterations obsd. on adsorption of the native IgG. The decrease in activity was much less pronounced in the range of surface coverage close to the plateau values. Possible mechanisms of adsorption of the hydrophobized forms of IgG are discussed. [on SciFinder(R)]

The analysis of media agenda and the multistages of four Israeli elections show a relation between real world indicators and the media coverage. The result also shows that the public opinion and voting had media influence than the president's performance during elections.

Effects of intermolecular hydrogen bonding between glycine and one water molecule on the vibrational spectrum are investigated, using ab initio (at the level of second order Moller-Plesset perturbation theory), empirical (OPLS-AA), and mixed ab initio/empirical quantum mechanics/molecular mechanics (QM/MM) potentials. Vibrational spectroscopy is calculated using the correlation corrected vibrational self-consistent field method that accounts for anharmonicities and couplings between different vibrational normal modes. The intermolecular hydrogen bonding interactions are found to be very strong and to affect vibrational frequencies and infrared intensities of both the glycine and the water molecule to a very large extent. The predicted ab initio anharmonic spectra can be used to identify amino acids in complexes with water in experimental studies. The OPLS-AA potential is found to describe hydrogen bonding between glycine and water incorrectly, and to predict erroneous vibrational spectra. Hybrid (QM/MM) techniques can, however, be used to calculate more reliable vibrational spectra, in agreement with full ab initio treatment of the whole system, provided that the regions that contain hydrogen bonds are described by ab initio potentials. (C) 2001 American Institute of Physics.