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The liquid crystalline phase of spider silk is thought to enable for the silk protein to be stored at high concentration in the gland without gelation, facilitating the instant fibre formation at the spinning duct. Nevertheless, it has never been revealed whether the liquid crystalline state of the silk protein maintains after the fibre formation. In this study, we conducted the X-ray liquid crystal structure analysis to reveal the details of molecular assemblies of the native spider silk proteins. Based on the wide- and small angle X-ray scattering data using the uniaxial bundle of spider draglines, the spider dragline silk fibres maintain a rectangular columnar liquid crystalline phase with a P21/a (p2gg) symmetry. The liquid crystalline state of the spider silk fibre is not nematic, cholesteric, nor hexagonal columnar, as previously proposed, but rectangularly packed columnar liquid crystal. The movable silk molecular chains along the long fibre axis in the rectangular columnar liquid crystalline structure help to explain the mechanical strength of the native spider dragline silk fibres. The results obtained in this study will contribute to understanding the biological basis underlying the silk fibre formation and will be useful to the biomimicry of spider silk fibres. [ABSTRACT FROM AUTHOR]

Resilin functions as an elastic spring that demonstrates extraordinary extensibility and elasticity. Here we use combined techniques, laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) to illuminate the structure and study the function of wing flexibility in damselflies, focusing on the genus Rhinocypha. Morphological studies using LSCM and SEM revealed that resilin patches and cuticular spikes were widespread along the longitudinal veins on both dorsal and ventral wing surfaces. Nanoindentation was performed by using atomic force microscopy (AFM), where the wing samples were divided into three sections (membrane of the wing, mobile and immobile joints). The resulting topographic images revealed the presence of various sizes of nanostructures for all sample sections. The elasticity range values were: membrane (0.04 to 0.16 GPa), mobile joint (1.1 to 2.0 GPa) and immobile joint (1.8 to 6.0 GPa). The elastomeric and glycine-rich biopolymer, resilin was shown to be an important protein responsible for the elasticity and wing flexibility. [ABSTRACT FROM AUTHOR]

The chemoenzymatic polymerization of amino acid monomers by proteases involves a two-step reaction: the formation of a covalent acyl-intermediate complex between the protease and the carboxyl ester group of the monomer and the subsequent deacylation of the complex by aminolysis to form a peptide bond. Although the initiation with the ester group of the monomer is an important step, the influence of the ester group on the polymerization has not been studied in detail. Herein, we studied the effect of the ester groups (methyl, ethyl, benzyl, and tert-butyl esters) of alanine and glycine on the synthesis of peptides using papain as the catalyst. Alanine and glycine were selected as monomers because of their substantially different affinities toward papain. The efficiency of the polymerization of alanine and glycine benzyl esters was much greater than that of the other esters. The benzyl ester group therefore allowed papain to equally polymerize alanine and glycine, even though the affinity of alanine toward papain is substantially higher. The characterization of the copolymers of alanine and glycine in terms of the secondary structure and thermal properties revealed that the thermal stability of the peptides depends on the amino acid composition and resultant secondary structure. The current results indicate that the nature of the ester group drastically affects the polymerization efficiency and broadens the substrate specificity of the protease.