Gas phase ion/molecule reactions in laser desorption mass spectrometry

The desorption of neutrals, alkali ions and quasimolecular ions of sucrose was studied as function of substrate temperature in laser desorption mass spectrometry. These phenomena were also investigated in thermal desorption experiments. It was concluded that in these experiments gas phase cationization is the major ionization process.     

Lattice dynamics of tetracyanoethylene

Lattice dynamics calculations for both crystalline forms of tetracyanoethylene are presented. The comparison of the calculated static and dynamical properties with the experimental data, leads us to suggest an improved parameter set for the “6-exp” potential function for crystals with cyano groups.     

Interactions of thiophenes and acidophilic,thermophilic bacteria

The growth and oxygen consumption of a variety of thermophilic, acidophilic bacteria in the presence of thiophene-2-carboxylate (T2C) and dibenzothiophene (DBT) have been determined. T2C was extremely toxic to the acidophiles in comparison with neutrophiles, but appeared to be degraded by a heterotrophicSulfolobus- like thermophile. DBT proved to be unstable at high temperatures, even in the absence of bacteria, and was not a substrate for the thermophiles.     

Characterisation of Sol-Gel TiO2 Films by Etching

This article describes the SmartKom Companion, one of three demonstrators developed within the SmartKom project whose goal has been to provide an intuitive and intelligent interface for non-expert users to everyday computer-based applications in different scenarios of use. Conceived for the SmartKom Mobile scenario, the Companion allows intuitive multimodal interaction for drivers and pedestrians. The development of the SmartKom prototypes was constantly accompanied by Wizard-of-Oz experiments as well as system evaluations at different stages of the project. Some usability evaluation results relative to the SmartKom Companion will also be presented.     

Spirophostins: conformationally restricted analogues of adenophostin A

The synthesis, biological evaluation, and molecular modeling of two conformationally restricted analogues of adenophostinA (1), denominated as spirophostin (3R)-10 and (3S)-11, as novel ligands for the D-myo-inositol 1,4,5-trisphosphate receptor (IP3R), is presented. These diastereoisomeric spiroketals are synthesized by spiroketalization of D-glucose derivatives (2S)-15 and (2R)-16, separation of the protected isomers (3R)-19 and (3S)-20, followed by phosphorylation and deprotection. The spirophostins (3R)-10 and (3S)-11 display comparable biological activity, with a 3H-IP3-displacing and Ca2+-releasing potency less than IP3 and adenophostin A.     

Preferred conformations of some 2-pyridyl substituted thiourea derivatives. A reinvestigation of NMR spectral data

A previous report involving ¹H nmr spectra of some 1-phenyl and 1-benzoyl 3-(2-pyridyl)thioureas was reinvestigated and found to be incorrect. Analysis of the data permits the designation of preferred conformations for these systems.     

MECHANISM OF PHOTOOXYGENATION OF THE CD (II) COMPLEX OF PYROPHEOPHORBIDE A METHYL ESTER

Photooxygenation of (pyropheophorbidato a methyl ester)cadmium (II) was studied using ^18,18O₂ labeling of the molecular oxygen required for cleavage of the macrocycle. After reductive demetallation of the primary oxidation product (4,5-dioxo-4,5-secopyropheophorbidato a methyl ester)cadmium (II), the isotope content of formylbilinone 4a was analyzed by repeated-scan fast atom bombardment mass spectrometry. Comparison of the spectroscopic data of the labeled pigment 4a with the statistical probabilities of¹⁸ O isotope incorporation calculated for four possible reaction mechanisms clearly proves that photooxidative ring cleavage occurred by the one-molecule mechanism, i.e. the terminal oxygen atoms of 4a were derived from one oxygen molecule. Furthermore, a study of the exchange of the¹⁸ O-labeled atoms revealed that no exchange occurs within the pH 4.5–9.5 range. In stronger alkaline or acidic solutions, only the oxygen atom of the formyl group is exchanged. Hydrolysis of the methyl ester group of 4a was achieved, without loss of the¹⁸ O label on the formyl group, at pH 7.2 in the presence of pig liver esterase.