Spectroscopy on the wing: Investigating possible differences in protein secondary structures in feather shafts of birds using Raman spectroscopy

Abstract

The central shaft of a bird’s flight feather bears most of the aerodynamic load during flight and exhibits some remarkable mechanical properties. The shaft comprises two parts, the calamus and the rachis. The calamus is at the base of the shaft, while the rachis is the longer upper part which supports the vanes. The shaft is composed of a fibrous outer cortex, and an inner foam-like core. Recent nanoindentation experiments have indicated that reduced modulus values, Er, for the inner and outer regions of the cortex can vary, with the Er values of the inner region slightly greater than those of the outer region.
In this work, Raman spectroscopy is used to investigate the protein secondary structures in the inner and outer regions of the feather cortex. Analysis of the Amide Iregion of Raman spectra taken from four birds (Swan, Gull, Mallard and Kestrel) shows that the β-sheet structural component decreases between the inner and outer region, relative to the protein side-chain components. This finding is consistent with the proposal that Er values are greater in the inner region than the outer region.
This work has shown that Raman spectroscopy can be used effectively to study the change in protein secondary structure between the inner and outer regions of a feather shaft.

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Identifiers

ORCID for Christian Laurent: orcid.org/0000-0002-2946-9705

ORCID for John Dyke: orcid.org/0000-0002-9808-303X

ORCID for Richard Cook: orcid.org/0000-0002-2468-5820

ORCID for Roeland De Kat: orcid.org/0000-0002-6851-4409

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