Cobweb….sounds familiar? With it’s spiral design to it’s sticky threads. They seem to be the most useless and good for nothing artwork on our walls and ceilings. But what if someone say that they are a marvel of protein engineering by nature. A structural combination of molecules arranged in such a fashion that even the modern day megastructures take inspiration from them. The sticky thread on these webs can be scientifically called as spider silk. As the name suggests, spider silk is woven by spider for the purpose of catching prey. This is very much different from the mulberry silk extracted from silkworm. The spider silk subunits are composed of Masp2 protein crystals. These protein molecules have anti parallel beta sheets in them The extensive beta linkages in them gives enormous tensile strength( even greater than reinforced steel). Feasible extraction of this silk protein can have numerous applications and we our in our way to provide a method for feasible extraction of spider silk
Our idea focuses on devising a method to produce silk proteins along with a monitoring mechanism with minimal cost and maximum output. We plan to produce the spider silk protein Masp2 from recombinant E.coli. We are targeting the mass production of spider silk protein Masp2 and a mechanism to extract it without the need of cell lysis. At present, we are restricting our idea up to monomer production, rather than thread production. We have also devised a method to characterise the amount of silk being produced and a way to monitor it.
The Masp2 protein also known as the major ampullate silk protein has acidic residues. In aqueous solution, the pH of the silk protein comes out to be near 4. Due to the presence of large number of acidic amino acids, the protein if produced inside recombinant e-coli,will remain in the cytoplasm.The only way to get them out is to lyse the cell. Our idea is to add a transmembrane protein Omp-A along with the silk protein, in order to anchor it to the membrane outside the cell The silk protein can be extracted by cleaving the linkage between Omp-A and Masp2 with an HIV protease. We have also put a histidine tag on the Masp-2 protein. The chelating effect of Histidine with Nickel atom will help us to extract the silk protein after cleavage. And isolate it on a nickel column. The silk protein construct can be added with multiple silk monomers according to the number of subunits desired.
The HIV protease required for cleavage action, will also be anchored to the membrane via the Omp-A protein. The protease will first carry out self cleavage in order to free itself from the membrane . Then the protease will cleave the silk protein from the membrane, releasing it into the solution. Nickel columns would be used in order to extract the silk monomers.
In order to characterise the amount of HIV protease required for this action, we have created a novel detection system based on FRET(Fluorescence Resonance Energy Transfer) pairs. This characterisation construct will have CFP and YFP attached with the same HIV cleavage site that we used in the silk construct and the protease construct. The construct will also have Omp-A in order to anchor it to the membrane. If the concentration of the protease will be high enough to perform the cleavage action on all the three constructs, then the YFP part will get cleaved and we will see a cyan fluorescence other wise due to the intact YFP part we will see a yellow fluorescence. The silk construct along with the FRET and the protease construct will provide us a mechanism for a continuous production of silk monomers without cell lysis and to monitor the silk production process.
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Stronger than steel but elastic than a rubber band, spider silk have dozen of potential application from construction, medicine to military. Scientists have suggested using spider silk to construct product as diverse as biodegradable water bottles, flexible bridge suspension cables and unrippable writing paper.
The early Roman and Greek populations used the silk to weave fabrics, create nets , create fishing lines and seal wounds. The material is used to make gloves and stockings, though the process take some time and required many spiders. The cross hairs on many weapons used spider silk, and to this day some military units still keep Black Widow spiders on site in case repairs to old weaponry are needed.
A. Lighter and Stronger Bulletproof Clothing:
Researcher melded human skin with the spider silk and the hybrid skin was able to repel a slow moving bullet fire by a .22-caliber rifle. If scaled up, spider silk body armor could be three times stronger than Kevlar. This technology can be very useful for military and automobile and flight industries. Artificial Skin: Growing artificial skin for burn victims is a tough task. We need a specific kind of scaffolding upon which to build the healthy skin tissue that can merge with the body. Collagen and synthetic fibres are typically used to provide support for growing skin tissue, but these materials are not biodegradable. The spider silk’s strength, flexibility and biodegradability may make it a nearly ideal matrix for growing skin and healing wounds. Air bags: if the air bags are made of spider silk than due to their higher elasticity and strength the air bags would absorb more energy and thus the sudden impact would be less injurious.
B. Artificial Skin:
Growing artificial skin for burn victims is a tough task. We need a specific kind of scaffolding upon which to build the healthy skin tissue that can merge with the body. Collagen and synthetic fibres are typically used to provide support for growing skin tissue, but these materials are not biodegradable. The spider silk’s strength, flexibility and biodegradability may make it a nearly ideal matrix for growing skin and healing wounds.
C. Air Bags:
If the air bags are made of spider silk than due to their higher elasticity and strength the air bags would absorb more energy and thus the sudden impact would be less injurious.
D. Medical Uses:
1. In injuries like torn interior cruciate ligament, spider silk due to its properties can be used to make a structure so that it can used as a artificial ligament.
2. As the spider silk is thinner, stronger and more elastic it can be used as surgical thread to stitch the wounds together.
Diverse and unique biomechanical properties together with biocompatibility and a slow rate of degradation make spider silks excellent candidates as biomaterials for tissue engineering, guided tissue repair and drug delivery, for cosmetic products