In the future, the fibers may be used to make protective vests, surgical suture threads, micro-conductors, optical fiber, fishing gear and clothing. An article about their research is published in the journal Current Biology
Image 1: on the right - fibers formed in insect cells; On the left - the web of the cross spider (courtesy of the Hebrew University). Image 2 (the left image): the web of the cruciferous spider (courtesy: Current Biology and the authors of the article).
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Silk produced from the cocoons of silk 'worms' has been used by humans for thousands of years; The spider silk that makes up the spider's webs is significantly stronger than him. However, the spider, unlike the silkworms, is a territorial animal that does not like to grow together and therefore cannot be domesticated and grown industrially on farms.
Scientists have tried to create spider webs through genetic engineering - independent of the spider - by producing the proteins responsible for creating the webs in organisms such as bacteria, yeast, plants and mammalian cells (in tissue culture). But the attempts to create in them fibers comparable in their properties to spider webs were not successful.
For the first time in the world, an Israeli-German research team succeeded in the spontaneous production of spider webs in insect cells. The engineered proteins produced by the researchers organized themselves into fibers with properties comparable to the fibers spun by the spider. Mass production of fibers could in the future be used in industry for fields that require minimal sizes. The Hebrew University's R&D Implementation Company and its partners from Germany handle the commercialization of the project.
In the study that lasted for about two years, the following participated: Dr. Uri Gat, a researcher in the field of developmental biology; PhD student Shmulik Yatah and research assistant Shula Cohen, from the Department of Cell Biology and Biochemistry at the Institute of Life Sciences at the Hebrew University of Jerusalem; Dr. Thomas Scheibel and research student Daniel Huemmerich, biophysicists from the Technical University of Munich; zoologist Fritz Vollrath from Oxford. An article about their research will be published in a cover story in the journal Current Biology (November 23.11.04, XNUMX).
Spider webs are made of special proteins that form the fibers. The researchers used gene segments of the cross spider (Araneus diadematus) that are responsible for coding proteins representative of the spider web proteins.
The spider weaves its web with different types of fibers including the frame fiber (Dragline Silk). This fiber is characterized by high basic stiffness and great elasticity, it is stronger (up to 6 times) than nylon and steel (of the same thickness) and is used by the spider as a lifeline when falling. The framework fiber consists mainly of two structural proteins of similar sequence ADF3 and ADF4 that are produced by a gland in the spider's abdomen and secreted from it to the outside of the spider's body to form the fiber. The path that the proteins take from the moment they are produced until they are secreted as fiber and the reason for the existence of two proteins were not understood by the researchers. The researchers inserted the genes coding for the two proteins into the genome of a virus that attacks insects called baculovirus. The viruses engineered to produce the proteins of the spider's fibers infected cells grown in culture originating from the larva of an insect similar to the processionary spinner.
"The spider and the insects both belong to the arthropod system. Since there is a higher genetic affinity between them than between the spider and the previous creatures that have been used so far, we thought of trying to produce the spider fibers in insect cells," says Dr. Uri Gat from the Hebrew University. We used a system for producing proteins in large quantities based on infecting insect cells with a virus for protein production."
The engineered viruses also contained the genes coding for the ADF3, ADF4 proteins. After infecting the insect cells with a virus, the cell systems become enslaved to the production of the proteins (coded by the genes of the virus) and produce the "spider" proteins. The researchers noticed that inside the infected insect cells fibers formed spontaneously from the ADF4 protein. The fibers were uniform in diameter and similar to the diameter of the fibers produced by the spider. Examining the chemical resistance properties of the resulting fiber revealed that it is equal and sometimes even surpasses the natural frame fiber. In contrast, the ADF3 protein was found to be soluble and did not form by itself or did not participate in the formation of the protein fiber structures.
The researchers hypothesize that the variation in the behavior of the proteins reveals another layer of the sophistication of the spider's fibers. It is possible that one protein (ADF4) enables the rapid formation of the fiber while the other (ADF3) controls its activity and prevents premature fiber formation that could be fatal to the spider. Now they hope to go beyond the limits of the volume of the insect cell and restore the conditions for the spontaneous creation of fibers - from the engineered proteins and different and improved versions of them - on the way to the mass production of fibers.
"The research allowed us to examine the close relationships that exist between the protein sequence, its structure and function," says Dr. Uri Gat. "From an applied point of view, mass production of fibers, one thousandth of a millimeter thick, may be used in the future for the production of protective vests, surgical suture threads, Microconductors, optical fiber, fishing equipment and even a new type of clothing."
Genome connoisseur - genetic engineering - animals
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