Silk protein

The secondary structure of a protein is the shape adopted by the polypeptide chain—in particular, how it coils or forms sheets. The order of the amino acids in the chain controls the secondary structure, because their intermolecular forces hold the chains together. The most common secondary structure in animal proteins is the a helix, a helical conformation of a polypeptide chain held in place by hydrogen bonds between residues (Fig. 19.19). One alternative secondary structure is the P sheet, which is characteristic of the protein that we know as silk. In silk, protein... 

Hayashi C. and Lewis R., Molecular architecture and evolution of a modular spider silk protein gene. Science, 287, 1477, 2000. 

Hayash C.I., Shipley N., and Lewis R., Hypotheses that correlate the sequence, structure, and mechanical properties of spider silk proteins, Int. J. Biol. Macromol., 24, 271, 1999. 

Parkhe AD, Seeley SK, Gardner K (1997) Structural studies of spider silk proteins in the fiber. J Mol Recognit 10 1-6... 

Silk fibers, a basic system with a uniaxial symmetry, have also been investigated by Raman spectromicroscopy [63] that is one of the rare techniques capable of providing molecular data on such small (3-10 pm diameter) single filaments. The amide I band of the silk proteins has been particularly studied to determine the molecular orientation using the cylindrical Raman tensor approximation. In this work, it was assumed that Co Ci, C2 and the a parameter was determined from an isotropic sample using the following expression of the depolarization ratio... 

Production of Spider Silk Proteins in Transgenic Tobacco and Potato... 

Tab.11.1 Spider silk proteins MaSpI, MaSpll and Flag from Nephila davipes.

Strategies for the Production of Recombinant Spider Silk Proteins... 

I I Synthetic spider silk protein SOI I I ER retention signal (KDEL)... 

Raw silk was dissolved in hexafluoro-iso-propanol (HFIP) [17, 33]. A typical working concentration for spinning was 2.5% (w/v) silk fibroin in HFIP. The spinning solution was pressed through a small needle (0 80-250 pm) into a precipitation bath (methanol for Bombyx mori silk proteins and acetone for Nephila clavipes silk proteins) and the silk solution immediately precipitated as a fiber. The best performing fibers approached the maximum strength measured for native fibers of Bombyx mori, but did not achieve the mechanical properties of natural spider silk. 

The spinning of silk monofilaments from a concentrated aqueous solution (>20% protein) of recombinant spider silk protein might be the best way to generate stress-... 

Synthetic Spider Silk Proteins for the In Vitro Proliferation of Anchorage-dependent Cells... 

Silk fibers or monolayers of silk proteins have a number of potential biomedical applications. Biocompatibility tests have been carried out with scaffolds of fibers or solubilized silk proteins from the silkworm Bombyx mori (for review see Ref. [38]). Some biocompatibility problems have been reported, but this was probably due to contamination with residual sericin. More recent studies with well-defined silkworm silk fibers and films suggest that the core fibroin fibers show in vivo and in vivo biocompatibility that is comparable to other biomaterials, such as polyactic acid and collagen. Altmann et al. [39] showed that a silk-fiber matrix obtained from properly processed natural silkworm fibers is a suitable material for the attachment, expansion and differentiation of adult human progenitor bone marrow stromal cells. Also, the direct inflammatory potential of silkworm silk was studied using an in vitro system [40]. The authors claimed that their silk fibers were mostly immunologically inert in short and long term culture with murine macrophage cells. 

Spider silk proteins from plants remain soluble at high temperatures, allowing them to be enriched by boiling [26]. In order to enrich the spider silk-ELP fusion protein, we therefore exposed tobacco leaf extracts to heat treatment at 95°C for 60 min and then cleared the supernatant by centrifugation. In further steps, the reversible precipitation behavior of ELP fusion proteins was exploited to develop a suitable purification strategy. For the selective precipitation of SOl-lOOxELP, NaCl was added at a final concentration of 2 M and the temperature was increased to 60 °C. In this man-... 

B. Silk Proteins Stability and Solubility in Solution Sol—Gel Transition. .. 25... 

III. Role and Function of ) -Sheet Assembly in Silk Proteins. 30... 

Silk proteins (spidroins in spiders and fibroins in Lepidoptera insects) are assembled into well-defined nanofibrillar architectures (Craig and Riekel, 2002 Eby et al., 1999 Inoue et al., 2000b, 2001 Li et al., 1994 Putthanarat et al, 2000 Vollrath et al., 1996). Spidroins and fibroins are largely constructed from two chemically distinct repetitive motifs or blocks (Table I), an insoluble crystalline block and a soluble less-crystalline block (Craig, 2003 Fedic et al., 2002 Hayashi and Lewis, 2000 Hayashi et al., 1999). The crystalline blocks are composed of short side-chained amino acids in highly repetitive sequences that give rise to /1-sheet structures. 

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