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Team:Newcastle/Research Feedback
From 2010.igem.org
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Voigt Paper
- Type III secretion system (T3SS) - exports proteins, translocates polypeptides through both the inner and outer membranes.
- Samonella Pathogenicity Island 1 (SP-1) - tool for export proteins of interest, can be applied to the recombinant production of spider silk proteins, which form fibrils if allowed to accumulate inside of confined volume of the cell.
- They've used the whole gene DNA synthesis to construct DNA sequences that matches exactly the wild type amino acid sequence for the known fragments of silk monomers.
- The synthetic genes were designed for 3 silk genes, from the spider named Araneus diadenatas.
- ADF-1: expressed in the minor ampullate gland, using during construction. High tensile strength, but inelastic.
- ADF-2: expressed in the cylindrical gland, used for egg sacks, sequence similar to human elastins.
- ADF-3: expressed in the major ampullate gland, forms extremely tough and elastic draglines which anchors the web.
- Each of the genes is expressed and exported using the Salmonella SP-1 T3SS.
Secretion control (Da)
In Gram-positive bacteria, proteins can be sorted to at least four different destinations: the cytoplasm, the cytoplasmic membrane, the cell wall and the extracellular medium.
By far the largest number of translocated and membrane proteins in Gram-positive bacteria are predicted to follow the general protein secretion (Sec) pathway, which involves SecA, SecY, SecE, SecG and a number of accessory proteins.
Sec secretion system in the rod-shaped bacterium Bacillus subtilis have been shown to localise in spirals along the cytoplasmic membrane.
The Tat secretion system, which is used for the transport of folded proteins, probably localises in the cytoplasmic membrane and at the cell poles of B. subtilis.
B. subtilis contains two Oxa1p (acts as a general membrane insertion machinery for proteins) homologues that involved in membrane protein biogenesis and in protein secretion, namely SpoIIIJ and YqjG . Both proteins are randomly distributed throughout the membrane and are thus not enriched in the vicinity of the Sec machinery.
Concrete properties
Concrete has a high compressive strength (3000 to 4000 psi) and a very low tensile strength (between 8% to 15% of the compressive strength). Cracking is due to the low tensile strength.
In reinforced concrete the steel reinforcement provides the tensile strength lacking in concrete. Steel has tensile strength equal to approximately 100 times that of concrete. Steel reinforcing is also capable of resisting compression forces.
Concrete and steel work very well together in relation to temperature changes because their coefficients of thermal expansion are quite close to each other. For steel it is 0.0000065 per unit length per degree Fahrenheit, while for concrete it is about 0.0000055.
Properties of calcium carbonate and spider silk
Calcium carbonate has a similar thermal expansion coefficient to concrete.
Some spider silks have a similar or better tensile strength than steel.
Glue, I haven't been able to find details of yet, but it is unlikely it has as good qualities.
Fibre-reinforced concrete. Addition of steel fibres (usually between 1% to 2% by volume) can appreciably improve their characteristics. Strength is not significantly improved, but significantly tougher and have greater resistance to cracking. The fibres used are usually from about 1/4 inch up to about 3 inches with diameters of 0.01 inch up to 0.03 inches. While a reinforcing bar provides reinforcing only in the direction of the bar, randomly distributed fibres provide additional strength in all directions.
Recommendation at the moment: calcium carbonate with spider silk.
However: which silks have been sequenced? Is silk alkali-resistant?
