The synthesis of diastereo- and enantiomerically pure beta-aminocyclopropanecarboxylic acids

The synthesis of diastereo- and enantiomerically pure beta-aminocyclopropanecarboxylic acids (beta-ACCs) is described. Starting from pyrrole, (rac)-4 is readily obtained, which was kinetically resolved by enzymatic hydrolysis. Subsequent oxidation of (-)-4 and deformylation gives rise to the cis-beta-ACC derivative (ent)-9, while (+)-10 was converted to the trans-beta-ACC derivative 8. Both 8 and (ent)-9 and their benzyl esters 13 and 16, being conformationally restricted beta-alanine or gamma-aminobutyric acid (GABA) derivatives, represent useful building blocks for peptides containing unnatural amino acids.     

Fluorescence interference-contrast microscopy on oxidized silicon using a monomolecular dye layer

A silicon chip is covered by a monomolecular film of a fluorescence dye with silicon dioxide used as a spacer. The fluorescence depends on the distance of the dye from the silicon. The modulation of the intensity is described quantitatively by an optical theory which accounts for interference of the exciting light and of the emitted light. The effect is used to obtain a microscopic picture of the surface profile with a precision of a few Angströms. The perspectives for an application in wet systems such as neuron-silicon junctions and lipid membranes on silicon are pointed out.     

Fluorescence of fly ash samples: Implications for in situ and remote detection

A study of the fluorescence spectra of fly ash samples from different sources has shown that each samples has a characteristic fluorescence and excitation spectrum which could be used to identify and monitor its presence. Fluorescence lifetime studies of samples from different sources have demonstrated characteristic features which can be used for identification. The fluorescence method should be useful for in situ and remote monitoring applications.