@article{rusa_bridges_ha_tonelli_2005, title={Conformational changes induced in Bombyx mori silk fibroin by cyclodextrin inclusion complexation}, volume={38}, ISSN={["1520-5835"]}, DOI={10.1021/ma050340a}, abstractNote={We have previously demonstrated that the formation of and coalescence from polymer−cyclodextrin (CD) inclusion compounds (ICs) represents a very useful approach to modify the chain conformations and improve the crystallinity of various bulk polymers. The present work deals, for the first time, with the formation of a γ-CD IC with a natural protein as guest, i.e., silk fibroin from Bombyx mori silkworm. Formation of the crystalline inclusion compound was verified by wide-angle X-ray diffraction, solid-state NMR, and infrared spectroscopy to have the host γ-CD molecules arranged in a channel structure, with the isolated silk chains included, at least in large part, in their internal cavities. Removing the γ-CD host lattice by washing with hot water produced a white coalesced silk sample that was collected and characterized. Unlike the original or precipitated silk fibroin, the coalesced sample shows most of its protein residues in a β-sheet conformation with an elevated degree of crystallinity.}, number={13}, journal={MACROMOLECULES}, author={Rusa, CC and Bridges, C and Ha, SW and Tonelli, AE}, year={2005}, month={Jun}, pages={5640–5646} }
 @article{ha_tonelli_hudson_2005, title={Structural studies of Bombyx mori silk fibroin during regeneration from solutions and wet fiber spinning}, volume={6}, ISSN={["1526-4602"]}, DOI={10.1021/bm050010y}, abstractNote={Regenerated silk fibroin materials show properties dependent on the methods used to process them. The molecular structures of B. mori silk fibroin both in solution and in solid states were studied and compared using X-ray diffraction, FTIR, and (13)C NMR spectroscopy. Some portion of fibroin protein molecules dissolved in formic acid already have a beta-sheet structure, whereas those dissolved in TFA have some helical conformation. Moreover, fibroin molecules were spontaneously assembled into an ordered structure as the acidic solvents were removed from the fibroin-acidic solvent systems. This may be responsible for the improved physical properties of regenerated fibroin materials from acidic solvents. Regenerated fibroin materials have shown poor mechanical properties and brittleness compared to their original form. These problems were technically solved by improving the fiber forming process according to a method reported here. The regenerated fibroin fibers showed much better mechanical properties compared to the native silk fiber and their physical and chemical properties were characterized by X-ray diffraction, solid state (13)C NMR spectroscopy, SinTech tensile testing, and SEM.}, number={3}, journal={BIOMACROMOLECULES}, author={Ha, SW and Tonelli, AE and Hudson, SM}, year={2005}, pages={1722–1731} }
 @article{ha_gracz_tonelli_hudson_2005, title={Structural study of irregular amino acid sequences in the heavy chain of Bombyx mori silk fibroin}, volume={6}, ISSN={["1526-4602"]}, DOI={10.1021/bm050294m}, abstractNote={Recently, genetic studies have revealed the entire amino acid sequence of Bombyx mori silk fibroin. It is known from X-ray diffraction studies that the beta-sheet crystalline structure (silk II) of fibroin is composed of hexaamino acid sequences of GAGAGS. However, in the heavy chain of B. mori silk fibroin, there are also present 11 irregular sequences, with about 31 amino acid residues (irregular GT approximately GT sequences). The structure and role of these irregular sequences have remained unknown. One of the most frequently appearing irregular sequences was synthesized and its 3-D solution structure was studied by high-resolution 2-D NMR techniques. The 3-D structure determined for this peptide shows that it makes a loop structure (distorted omega shape), which implies that the preceding backbone direction is changed by 180 degrees, i.e., reversed, by this sequence. This may facilitate the beta-sheet formation between the crystal-forming building blocks, GAGAGS/GY approximately GY sequences, in the fibroin heavy chain.}, number={5}, journal={BIOMACROMOLECULES}, author={Ha, SW and Gracz, HS and Tonelli, AE and Hudson, SM}, year={2005}, pages={2563–2569} }