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Acta Cryst. (2014). A70, C1238
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The first coordination sphere of spin crossover material has been comprehended to play a dominant role to its magnetic property. However, the intermolecular interactions, such as π···π interaction and hydrogen bonding, also play a crucial factor. The contents of the solvent in a 2D layer structure, Fe (μ-atrz)(μ-pyz)(NCS)2·nH2O where n=4, 2 and 0, has been reported to be able to affect the spin transition behavior dramatically.[1] As loss of solvent molecules, the inter-layer distance becomes shorter and the transition temperature shifts to lower temperature and accompanies a larger hysteresis loop. To further understand the correlation between the inter-layer distance and magnetic property, the guest ab/desorption and pressure-induced synchrotron powder diffraction experiments were performed at BL01C2 in NSRRC. Based on the cyclic TGA measurements, the guest molecules, H2O, MeOH and EtOH, all can be removed and retaken repeatedly. The pressure-induced PXRD experiment was performed using a Boehler-Almax design diamond anvil cell (DAC). The detail structural studies attempt to understand not only the spin state changes from HS (high spin state) to LS (low spin state) but also the cooperative effect through the inter-layer distance.

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Acta Cryst. (2014). A70, C1322
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Spider dragline silk is one of the strongest nature fibers and some of their features are even better than those of the best synthetic fibers. Understanding the mechanisms inducing silk variability may have implications for biomimetics and the synthesis of environmentally responsive materials. Dragline silk contains both elasticity (amorphous) and crystalline regions. Our previous studies had demonstrated that spiders might vary the protein composition and thus physical properties of silks when experiencing food with different nutrient level. In this study we fed Nephila pilipes with high, low and no protein foods and collected their dragline silks for synchrotron Radiation (SR) wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) examinations. The WAXS data showed a significant difference in crystalline fractions of dragline silks produced by N. pilipes experiencing different food treatments. In addition, the orientation of crystallines also varied considerably among silks produced by spiders in three treatment groups. The SAXS data, obtained with the beam incident along and perpendicular to the fiber axis revealed a mesostructure comprising nano crystallites (beta sheets) stack spirally along the spider fibril axis. Such results indicate that spiders experiencing different nutrient stress level might produce dragline silks of different physical properties due to variations in crystalline density, orientation and the meso-phase structures in nano scale. Furthermore, varying environmental wind strength leads to changes in tensile mechanics of spider dragline silk hence produced. Exposing the spider Cyclosa mulmeinensis to controlled stress from constant airflow, we found correlated changes in (i) amino acid composition, (ii) tensile mechanics and (iii) crystallinity, of the dragline silk; which results suggest that protein variation and/or post secretion crystalline variations are associated with the mechanical properties of the spider silks.
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