Silk and wool are well-known protein-based fibers. Their environmental stability, biocompatibility, and unique mechanical properties provide an important basis for using these natural proteins in biomedical applications. To use them as biomaterials in the form of fibers, films, or membranes, it is necessary to characterize these proteins in their Solution and solid states because structural characteristics and morphological features have a great influence on the physical and mechanical properties of these new regenerated protein forms. Therefore, in the present study, silk fibroin and wool keratin were dissolved and their solution behaviors and secondary structures are analyzed and compared, using particle size distribution, molecular weight distribution (SDS-PAGE), Fourier transform infrared, and X-ray diffraction techniques. It was shown that keratin is more stable in solution and more amorphous in the solid state. (c) 2006 Wiley Periodicals, Inc.