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PubMed1974

Tanned silks.

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Animals↗
PubMed1975

Desmosomes, filaments, and keratohyaline granules: their role in the stabilization and keratinization of the epidermis.

Components of desmosomes, filaments, and keratohyaline granules were studied by electron microscope and biochemical methods to clarify their role in the stabilization and keratinization of the epidermis. Isolated desmosomes are composed of 76% protein, 17% carbohydrate, and 10% lipid. The bulk of protein consists of a "spectrin"-like fibrous protein, presumably present in the plaque, and of glycoproteins in the desmosomal interspace. The main component of filaments, prekeratin, is a low-sulfur alpha-protein composed of a pair of three-chain subunits with non-alpha-helical segments separated by 200 A-long alpha-helical regions. The major component of isolated keratohyaline granules, the amorphous particulate material, is formed by a high-sulfur protein with a single-type of polypeptide chain. Polypeptide chains comparable to those found in prekeratin and keratohyaline granules were recovered from extracts of horny cells. Within the living part of the epidermis, filaments hypothetically form a cytoskeletal system which is anchored to desmosomes by a filamentous plaque protein. Glycoproteins are involved in the formation of strong junctions between the cells which enable the living part of the epidermis to respond as a whole to mechanical stress. The stratum corneum is stabilized by a similar system in a consolidated state which is less extensible. Horny cells are enveloped by a thickened membrane and the interfilamentous spaces are filled with various proteins including the sulfur-rich amorphous protein found in keratohyaline granules.

Animals↗
PubMed2002

Spider silk fibers spun from soluble recombinant silk produced in mammalian cells.

Spider silks are protein-based "biopolymer" filaments or threads secreted by specialized epithelial cells as concentrated soluble precursors of highly repetitive primary sequences. Spider dragline silk is a flexible, lightweight fiber of extraordinary strength and toughness comparable to that of synthetic high-performance fibers. We sought to "biomimic" the process of spider silk production by expressing in mammalian cells the dragline silk genes (ADF-3/MaSpII and MaSpI) of two spider species. We produced soluble recombinant (rc)-dragline silk proteins with molecular masses of 60 to 140 kilodaltons. We demonstrated the wet spinning of silk monofilaments spun from a concentrated aqueous solution of soluble rc-spider silk protein (ADF-3; 60 kilodaltons) under modest shear and coagulation conditions. The spun fibers were water insoluble with a fine diameter (10 to 40 micrometers) and exhibited toughness and modulus values comparable to those of native dragline silks but with lower tenacity. Dope solutions with rc-silk protein concentrations >20% and postspinning draw were necessary to achieve improved mechanical properties of the spun fibers. Fiber properties correlated with finer fiber diameter and increased birefringence.

Amino Acid Motifs↗
PubMed2006

Silk genes support the single origin of orb webs.

The orb web is a spectacular evolutionary innovation that enables spiders to catch flying prey. This elegant, geometric structure is woven with silk fibers that are renowned for their superior mechanical properties. We used silk gland expression libraries to address a long-standing controversy concerning the evolution of the orb-web architecture. Contrary to the view that the orb-web design evolved multiple times, we found that the distribution and phylogeny of silk proteins support a single, ancient origin of the orb web at least 136 million years ago. Furthermore, we substantially expanded the repository of silk sequences that can be used for the synthesis of high-performance biomaterials.

Animals↗
PubMed1996

Molecular orientation and two-component nature of the crystalline fraction of spider dragline silk.

The molecular origin of the exceptional mechanical properties of spider silk is unclear. This paper presents solid-state 2H nuclear magnetic resonance data from unoriented, oriented, and supercontracted fibers, indicating that the crystalline fraction of dragline silk consists of two types of alanine-rich regions, one that is highly oriented and one that is poorly oriented and less densely packed. A new model for the molecular-level structure of individual silk molecules and their arrangement in the fibers is proposed. These data suggest that it will be necessary to control the secondary structure of individual polymer molecules in order to obtain optimum properties in bio-inspired polymers.

Alanine↗