Non-destructive NIR-FT-Raman spectroscopy of plant and animal tissues, of food and works of art.

Just after the discovery of Raman spectroscopy in 1928, it became evident that fluorescence with a quantum yield of several orders of magnitude higher than that of the Raman effect was a great and apparently unbeatable competitor. Raman spectroscopy could therefore, in spite of many exciting advantages during the last 60 years, not be applied as an analytical routine method: for nearly every sample, fluorescing impurities had to be removed by distillation or crystallisation. Purification, however, is not possible for cells and tissues, since the removal of the fluorescing enzymes and coenzymes would destroy the cells.

Non-destructive Raman analyses--polyacetylenes in plants.

Ferdinand Bohlmann has described the isolation, the identification and the structure elucidation of acetylene compounds in many plants, and confirmed it by its synthesis. We have recorded the Raman spectra of most of these plants non-destructively by FT-Raman spectroscopy using radiation at 1064 nm. We could not observe any interfering fluorescence.

In vivo evidence for compromised phenylalanine metabolism in vitiligo.

Human epidermal melanocytes and keratinocytes express mRNA for all enzymes involved in de novo synthesis/recycling of the cofactor (6R) L-erythro 5,6,7,8 tetrahydrobiopterin (6BH4) in normal healthy individuals. An enhanced epidermal de novo synthesis was identified in association with decreased epidermal phenylalanine hydroxylase and 4a carbinolamine dehydratase in patients with vitiligo. The latter event leads to an accumulation of the nonenzymatic isomer (7R) L-erythro 5,6,7,8 tetrahydrobiopterin (7BH4) inhibiting phenylalanine hydroxylase (PAH) with an apparent Ki = 10(-6) M.

Fourier-transform Raman spectroscopy applied to photobiological systems.

Fluorescence and initiation of photoreactions are problems frequently encountered with resonance Raman spectroscopy of photobiological systems. These problems can be circumvented with Fourier-transform Raman spectroscopy by using the 1064-nm wavelength of a continuous wave neodymium-yttrium/aluminum-garnet laser as the probing beam. This wavelength is far from the absorption band of most pigments.