Melanin discrimination in feathers by Raman spectroscopy

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  • Published: Apr 11, 2015
  • Author: Steve Down
  • Channels: UV/Vis Spectroscopy / Raman / Infrared Spectroscopy / Base Peak / X-ray Spectrometry / Atomic / Chemometrics & Informatics / Proteomics / MRI Spectroscopy / NMR Knowledge Base

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Contrary to previous reports, Raman spectroscopy can be used to distinguish and measure melanins in feathers, according to Spanish scientists.

There has been some disagreement in the literature on whether Raman spectroscopy can distinguish different melanins in feathers. Scientists at the Donana Biological Station (EBD-CSIC) in Seville recently described a procedure which did so but this was contradicted by another study in which the Raman spectra of melanins were characterised by fluorescence artifacts. In a follow-up study a year later, the same authors reported that melanins do have a distinctive spectrum but that they cannot be distinguished from each other.

Now, the Spanish team, led by Ismael Galvan, have analysed feathers from the same species of birds that were examined in the conflicting work to try and clear up the differences. They found that discrimination is possible using confocal Raman spectroscopy. However, as they explained in Ecology and Evolution, the excitation wavelength is crucial for melanin analysis.

The successful wavelength was 780 nm, with eumelanin and phaeomelanin both detected and distinguished. Excitation at 532 nm failed, probably due to the fragility of the feathers that were damaged by the high-energy irradiation. On the other hand, excitation at 1032 nm also failed, probably as it was insufficiently energetic to generate scattered photons for detection.

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