This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.ABSTRACT: Avian structural colors are produced by biological 'photonic crystals' which are nanoscale structures with periodic variation in refractive index. These colors are produced by coherent scattering of visible light by the nanostructures. In previous research, we have examined structural color production by the spongy medullary keratin of avian feather barbs (Prum et al. 1998; Prum et al. 1999b; Prum et al. 2003) and by arrays of parallel collagen fibers in avian (Prum et al. 1999a; Prum and Torres 2003b) and mammalian (Prum and Torres 2004) skin. We have developed a method using Fourier analysis of the variation in refractive index from TEM micrographs to predict the color produced various tissues (Prum and Torres 2003a). In our previous work, a persistent source of error in understanding the optics of these tissues has come from studying the 3D amorphous, or quasi-ordered, tissues using 2D images. These nanostructures are so complex that we cannot appropriately characterize their periodicity from a average of 2D images. We would like to explore the possibility of obtaining 3D tomographic data sets to better characterize these tissues. Similar techniques have recently been dapplied to color producing butterfly scales (Argyros et al. 2002). The first proposed study would be to examine feather barbs of Cotinga and Lepidothrix, which produce vivid structural blues (Figs 1-2). The nanostructures in these feathers are composed of beta-keratin and air. Ideally, we would obtain a cubic 'stack' images that are 1024 x 1024 pixels in a stack (I don't know how sparsely the z-dimension is sampled, but the more the better for us). The stack of images would be used to analyze the color production by these tissues. Fig. 1 Lepidothrix nattereri (x30K) Fig. 2 Cotinga cayana (x20K)References Argyros, A., M. C. J. Large, D. R. McKenzie, G. C. Cox, and D. M. Dwarte. 2002. Electron tomography and computer visualization of a three-dimensional 'photonic' crystal in a butterfly wing-scale. Micron 33:483-487.Prum, R. O., S. Andersson, and R. H. Torres. 2003. Coherent scattering of ultraviolet light by avian feather barbs. Auk 120:163-170.Prum, R. O., and R. H. Torres. 2003a. A Fourier tool for the analysis of coherent light scattering by bio-optical nanostructures. Integrative and Comparative Biology 43:591-602.Prum, R. O., and R. H. Torres. 2003b. Structural colouration of avian skin: convergent evolution of coherently scattering dermal collagen arrays. Journal of Experimental Biology 206:2409-2429.Prum, R. O., and R. H. Torres. 2004. Structural colouration of mammalian skin: convergent evolution of coherently scattering dermal collagen arrays. Journal of Experimental Biology 207:2157-2172.Prum, R. O., R. H. Torres, C. Kovach, S. Williamson, and S. M. Goodman. 1999a. Coherent light scattering by nanostructured collagen arrays in the caruncles of the Malagasy asities (Eurylaimidae: Aves). Journal of Experimental Biology 202:3507-3522.Prum, R. O., R. H. Torres, S. Williamson, and J. Dyck. 1998. Coherent light scattering by blue feather barbs. Nature 396: 28-29.Prum, R. O., R. H. Torres, S. Williamson, and J. Dyck. 1999b. Two-dimensional Fourier analysis of the spongy medullary keratin of structurally coloured feather barbs. Proceedings of the Royal Society London B 266:13-22.
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