Comparative evaluation of Raman spectroscopy at different wavelengths for extremophile exemplars

Villar, S.E. Jorge; Edwards, H.G.M.; Worland, M.R.. 2005 Comparative evaluation of Raman spectroscopy at different wavelengths for extremophile exemplars. Origins of Life and Evolution of the Biospheres, 35. 489-506.

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Raman spectra have been obtained for extremophiles from several geological environments; selected examples have been taken from hot and cold deserts comprising psychrophiles, thermophiles and halophiles. The purpose of this study is the assessment of the effect of the wavelength of the laser excitation on the ability to determine unique information from the Raman spectra about the specificity of detection of biomolecules produced as a result of the survival strategies adopted by organisms in extreme terrestrial environments. It was concluded that whereas FT-Raman spectroscopy at 1064 nm gave good quality results the time required to record the data was relatively large compared with other wavelengths of excitation but that better access to the CH stretching region for organic molecules was given. Shorter wavelength excitation of biomolecules in the blue-green regions of the visible spectrum using a conventional dispersive spectrometer was more rapid but very dependent upon the type of chemical compound being studied; most relevant biomolecules fluoresced at these wavelengths but carotenoids exhibited a resonance effect which resulted in an improved detection capability. Minerals and geological materials, in contrast, were best studied at these visible wavelengths. In general, the best compromise system for the excitation of the Raman spectra of both geological and biological materials was provided using a 785 nm laser coupled with a dispersive spectrometer, especially for accessing the 1800–200 cm−1 wavenumber shift region where much of the definitive analytical information resides. This work will have conclusions relevant to the use of miniaturised Raman spectrometers for the detection of biomolecules in extraterrestrial planetary exploration.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > Antarctic Science in the Global Context (2000-2005) > Life at the Edge - Stresses and Thresholds
Additional Keywords: biosignatures, extremophile, planetary exploration, Mars, Raman spectroscopy, wavelength laser excitation
Date made live: 20 Jan 2012 09:05 +0 (UTC)

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