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The C 1s spectral features are interpreted with the aid of ab initio calculation for core excitation of benzene, biphenyl, hexafluorobenzene, and decafluorobiphenyl. A weak feature at 287.7 eV in biphenyl is identified as a C 1s -->pi(super *)(sub deloc) transition, characteristic of ring-ring delocalization and its intensity and position are shown to be related to the average torsion angle.

The C 1s, Si 2p, Si 2s and O 1s inner-shell excitation spectra of vinyltriethoxysilane, trimethylethoxysilane and vinyltricetoxysilane is recorded by electron energy loss spectroscopy under scattering conditions dominated by electric dipole transitions. The use of the measurements in assisting chemistry studies of adhesion promoters for electronic applications is discussed.

A systematic study results for the sodium dodecyl sulfate (SDS)-solubilized states of a series of model [alpha]-helical transmembrane (TM) segments of varying Ala and Ile content in conjunction with selected single-Asn polar substitutions are presented. The detergent micelles formed from SDS which exhibit ability to mimick the tertiary interactions of protein-, lipid-, and aqueous-exposed helical surfaces that arise in the folded TM domains of proteins could be used to gain insight into similar TM sequences in the in vivo assembly of polytopic membrane proteins.

A complete analysis of various peptide models is conducted to explain the structures of the various membrane proteins with modified properties. These proteins are shown to be extremely useful, as they can be easily used in various cellular processes and drug treatments.

The use of second-harmonic generation at different wavelengths to compare the resonant contributions of two simple dipolar chromophores, nitroaniline and nitrosulfenamide is reported. The result shows that pi intermolecular interaction does result in excitations that are observable in the linear spectrum of nitroaniline and thus could have an influence on the nonlinear response.

C 1s electron energy loss spectra of gaseous benzene, naphthalene, anthracene, phenanthracene, triphenylene, pyrene, and 1,2-benzanthracene are recorded under dipole conditions. Comparison of the spectra by two techniques indicates the dipole approximation is likely valid for the XRS results. The study will be valuable while using XRS to characterize more complex systems with unknown fused ring composition.

α-Helical transmembrane (TM) segments in membrane proteins are comprised primarily of hydrophobic amino acids that accommodate inser- tion from water into the nonpolar membrane biayer. In many such segments, however, polar residues are also present for structural or functional reasons. These latter residues impair the local favorable acyl interactions required for solvation by hydrophobic media such as phospholipids in native bilayers or detergents used for in vitro characterization. Using a series of Lys-tagged designed TM-like peptides (typified by KK-YAAAIAAIAWAIAAIAAAIAA- KICK) in which single-Asn residue substitutions (from lie or Ala) were made successively from the center of the hydrophobic region toward the C-terminus, we demonstrate that polar residues strongly alter the nature of the interaction between TM segments and the solvating detergent. Through the application of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectroscopy, and tryptophan fluorescence, we observed drastic differences in the structures of the detergent-peptide complexes that contain relatively minor sequence differences. For example, the blue shift of the Trp fluorescence (indicating local detergent solvation at this location) differs by as much as ∼10 nm depending upon the position of a single Mn substitution in an otherwise identical segment. The overall results suggest that polar point mutations occurring in a biological membrane will elicit comparable effects, placing a significant refolding burden on the local protein structure and potentially leading to disease states through altered protein-lipid interactions in membrane proteins. [ABSTRACT FROM AUTHOR]