Two-dimensional Fourier analysis of the spongy medullary keratin of structurally coloured feather barbs
Two-dimensional Fourier analysis of the spongy medullary keratin of structurally coloured feather barbs
复制标题
DOI：
10.1098/rspb.1999.0598
复制
发表时间：
1999-01-07
影响因子：
4.7
通讯作者：
Dyck, J
中科院分区：
文献类型：
--
作者：
Prum, RO;Torres, R;Dyck, J
我们进行了二维（2D）离散傅立叶分析的空间变化的海绵髓质角蛋白的折射率从四个不同颜色的结构彩色羽毛倒钩从三种鸟：玫瑰脸的爱情鸟，Agapornis roseicollis（鹦鹉科），虎皮鹦鹉，Melopsittacus undulatus（鹦鹉科），和Gouldian雀，Poephila guttata（Estrildidae）。这些结果表明，海绵状髓质角蛋白是一个纳米结构的组织，作为一个阵列的相干散射。髓质角蛋白的纳米结构在所有方向上几乎是均匀的。组织中折射率的空间变化的最大傅立叶分量具有适当的大小，以仅通过相长干涉产生所观察到的颜色。由二维傅立叶功率谱计算的反射谱预测值与显微分光光度法测得的反射谱峰一致。产生这些颜色的替代物理模型，瑞利和米氏理论，假设髓角蛋白是一个不相干的阵列，散射波是独立的相位。这一假设被这些羽毛的环状傅立叶功率谱和髓角蛋白中散射空泡的间距所证伪。鸟类羽毛倒钩的结构颜色是由相干散射光波的建设性干涉产生的，这些相干散射光波来自海绵髓层中的角蛋白和空气的光学异质基质。
We conducted two-dimensional (2D) discrete Fourier analyses of the spatial variation in refractive index of the spongy medullary keratin from four different colours of structurally coloured feather barbs from three species of bird: the rose-faced lovebird, Agapornis roseicollis (Psittacidae), the budgerigar, Melopsittacus undulatus (Psittacidae), and the Gouldian finch, Poephila guttata (Estrildidae). These results indicate that the spongy medullary keratin is a nanostructured tissue that functions as an array of coherent scatterers. The nanostructure of the medullary keratin is nearly uniform in all directions. The largest Fourier components of spatial variation in refractive index in the tissue are of the appropriate size to produce the observed colours by constructive interference alone. The peaks of the predicted reflectance spectra calculated from the 2D Fourier power spectra are congruent with the reflectance spectra measured by using microspectrophotometry. The alternative physical models for the production of these colours, the Rayleigh and Mie theories, hypothesize that medullary keratin is an incoherent array and that scattered waves are independent in phase. This assumption is falsified by the ring-like Fourier power spectra of these feathers, and the spacing of the scattering air vacuoles in the medullary keratin. Structural colours of avian feather barbs are produced by constructive interference of coherently scattered light waves from the optically heterogeneous matrix of keratin and air in the spongy medullary layer.