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 I region 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.

中文翻译：

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翅膀上的光谱：使用拉曼光谱研究鸟类羽毛轴中蛋白质二级结构的可能差异。

鸟类飞行羽毛的中心轴承受着飞行过程中的大部分空气动力载荷，并表现出一些显着的机械性能。轴由两部分组成，菖蒲和轴。菖蒲位于轴的底部，而轴是支撑叶片的较长的上部。轴由纤维状外皮层和内部泡沫状核心组成。最近的纳米压痕实验表明，皮质内部和外部区域的降低模量值 Er 可能会有所不同，内部区域的 Er 值略大于外部区域的值。在这项工作中，拉曼光谱用于研究羽毛皮层内部和外部区域的蛋白质二级结构。对来自四只鸟类（天鹅、海鸥、Mallard 和 Kestrel) 表明，相对于蛋白质侧链成分，β-折叠结构成分在内部和外部区域之间减少。这一发现与内部区域的 Er 值大于外部区域的提议一致。这项工作表明，拉曼光谱可以有效地用于研究羽毛轴内部和外部区域之间蛋白质二级结构的变化。