Silk, which forms the radial threads of the web, consists of two proteins that determine its strength and elasticity. Each protein contains three regions with different properties. The former forms an amorphous (non-crystalline) stretchable matrix that gives silk its elasticity. When an insect hits the web, the matrix expands to absorb the kinetic energy of the collision with the insect. The stiffness of silk is given by two types of crystalline regions embedded in the amorphous regions of each of the proteins. Both of these areas have a close-packed structure and are not amenable to stretching, with one of them having a rigid structure. It is believed that the crystalline regions with a less rigid structure hold the rigid crystalline structures together with the amorphous matrix.
The thickness of the web thread is only
0,1
the diameter of a human hair, but several times stronger than steel wire of the same weight. In the Spider-Man movie, the strength of the web is greatly underestimated.
The explanation comes from biologist William K. Purves of Harvey Mudd College.
The abdomen of the spider is enlarged 12 tons. Factory for the production of cobwebs.
From the movable tubes, a protein squirts out, which, once in the air, hardens, forming a high-strength thread.
In the picture on the left is Kevlar, and on the right is a nanotube - a carbon fiber. Tests show more than a threefold improvement in strength. And this is just the beginning.
The cross section of a thread, wire, even a web, no matter how small it may be, still has a certain geometric shape, most often the shape of a circle. In this case, the cross-sectional diameter or, let's say, the thickness of one web is approximately 5 microns (5 }
Mm. Is there anything thinner than a web? Who
U000 ) U U
the most skillful "fine spinner"? A spider or maybe a silkworm? No. The diameter of the thread of natural silk is 18 microns, i.e. the thread is 3" / 2 times thicker than one web.
People have long dreamed of surpassing the art of the spider and the silkworm with their skill. There is an old legend about the amazing weaver, the Greek woman Arachne. She mastered the craft of weaving to such perfection that all the fabrics were as thin as cobwebs, transparent as glass, and light as air. Athena herself, the goddess of wisdom and the patroness of crafts, could not compete with her.
Rice. 162.
This legend, like many other ancient legends and fantasies, has become a reality in our time. Modern Arachnea, the most skillful "fine spinner", turned out to be chemical engineers who created an unusually thin and surprisingly strong artificial fiber from ordinary wood. Silk threads, obtained, for example, by the industrial copper-ammonia method, are 2'/g times thinner than cobwebs, and are almost inferior in strength to natural silk threads. Natural silk can withstand loads up to 30 kg per 1 sq. mm of cross section, and copper ammonia - up to 25 kg per 1 sq. mm.
The method of making copper-ammonia silk is curious. The wood is converted into cellulose, and the cellulose is dissolved in an ammonia solution of copper. Jets of the solution are poured into water through thin holes, the water takes away the solvent, after which the resulting threads are wound on appropriate devices. The thickness of the copper ammonium silk thread is 2 microns. Its so-called acetate, also artificial, silk is 1 micron thicker. The amazing thing is that some varieties of acetate silk are stronger than steel wire! If a steel wire can withstand a load of 110 kg per square millimeter of cross-section, then an acetate silk thread can withstand 126 kg per 1 square. mm.
Rice. 163.
The well-known viscose silk, which is well known to all of us, has a thread thickness of about 4 microns, and an ultimate strength of 20 to 62 kg per 1 sq. mm cross section. On fig. 162 shows the comparative thickness of the web, human hair, various artificial fibers, as well as wool and cotton fibers, and in fig. 163 - their fortress in kilograms per 1 sq. mm. Artificial, or, as it is also called, synthetic, fiber is one of the largest modern technical discoveries and is of great economic importance. Here is what engineer Buyanov says: “Cotton grows slowly, and its quantity depends on the climate and the crop. The manufacturer of natural silk - the silkworm - is extremely limited in its capabilities. During his life, he will spin a cocoon, in which there is only 0.5 g of silk thread ...
The amount of artificial silk obtained by chemical processing from 1 cu. m of wood, replaces 320,000 silk cocoons or an annual wool shear from 30 sheep, or an average cotton yield per 1/g ha. This amount of fibers is enough to produce four thousand pairs of women's stockings or 1500 m of silk fabric.
Spiders belong to the oldest inhabitants of the Earth: traces of the first arachnids were found in rocks that are 340–450 million years old. Spiders are about 200-300 million years older than dinosaurs and more than 400 million years older than the first mammals. Nature had enough time not only to multiply the number of spider species (about 60 thousand of them are known), but also to equip many of these eight-legged predators with an amazing means of hunting - cobwebs. The pattern of the web can be different not only for different types, but also in one spider in the presence of certain chemicals, such as explosives or narcotics. Spiders were even going to be launched into space to study the effect of microgravity on the pattern of the web. However, most of all mysteries were hidden by the substance of which the web consists.
The web, like our hair, animal hair, silkworm threads, consists mainly of proteins. But the polypeptide chains in each cobweb are intertwined in such an unusual way that they have gained almost a record strength. The single thread produced by the spider is as strong as steel wire of equal diameter. A rope woven from cobwebs, only about the thickness of a pencil, could hold a bulldozer, a tank, and even such a powerful airbus as a Boeing 747 in place. But the density of steel is six times greater than that of cobwebs.
It is known how high the strength of silk threads is. A classic example is an observation made by an Arizona doctor as early as 1881. In front of this doctor, a shootout took place in which one of the shooters was killed. Two bullets hit the chest and went right through. At the same time, pieces of a silk handkerchief stuck out from the back of each wound. The bullets went through clothing, muscle and bone, but failed to tear through the silk they encountered.
Why, then, are steel structures used in engineering, and not lighter and more elastic ones made of a material similar to cobwebs? Why are silk parachutes not replaced by the same material? The answer is simple: try to make such material that spiders easily produce daily - it will not work!
Scientists from around the world have long studied the chemical composition of the web of eight-legged weavers, and today the picture of its structure has been more or less fully disclosed. The web filament has an inner core of a protein called fibroin and surrounding this core are concentric layers of glycoprotein nanofibers. Fibroin makes up approximately 2/3 of the mass of the web (and also, by the way, of natural silk fiber). It is a viscous, syrupy liquid that polymerizes and solidifies in air.
Glycoprotein fibers, which may be only a few nanometers in diameter, may be parallel to the axis of the fibroin filament or form spirals around the filament. Glycoproteins - complex proteins that contain carbohydrates and have a molecular weight of 15,000 to 1,000,000 amu - are present not only in spiders, but also in all tissues of animals, plants and microorganisms (some proteins in blood plasma, muscle tissues, cell membranes, etc.).
During the formation of the web, glycoprotein fibers are interconnected due to hydrogen bonds, as well as bonds between CO and NH groups, and a significant proportion of bonds are formed in the arachnoid glands of arachnids. Glycoprotein molecules can form liquid crystals with rod-shaped fragments that are stacked parallel to each other, which gives the structure the strength of a solid while maintaining the ability to flow like a liquid.
The main components of the web are the simplest amino acids: glycine H 2 NCH 2 COOH and alanine CH 3 CHNH 2 COOH. The web also contains inorganic substances - potassium hydrogen phosphate and potassium nitrate. Their functions are reduced to protecting the web from fungi and bacteria and, probably, creating conditions for the formation of the thread itself in the glands.
A distinctive feature of the web is environmental friendliness. It consists of substances easily absorbed by the natural environment and does not harm this environment. In this regard, the web does not yet have analogues created by human hands.
A spider can distinguish up to seven threads of different structure and properties: some for trapping "nets", others for its own movement, others for signaling, etc. Almost all of these threads could be widely used in industry and everyday life if would be able to establish their wide production. However, it is hardly possible to “tame” spiders, like silkworms, to organize peculiar spider farms: the aggressive habits of spiders and the traits of an individual farmer in their character are unlikely to allow this. And for the production of just 1 m of fabric from the web, more than 400 spiders are required to “work”.
Is it possible to reproduce the chemical processes that take place in the body of spiders and copy natural material? Scientists and engineers have long developed the technology of Kevlar - aramid fiber:
obtained on an industrial scale and approaching the properties of the web. Kevlar fibers are five times weaker than cobwebs, but still so strong that they are used to make light bulletproof vests, protective helmets, gloves, ropes, etc. But Kevlar is obtained in hot sulfuric acid solutions, while a spider needs ordinary temperature. Chemists do not yet know how to approach such conditions.
However, biochemists approached the solution of the material science problem. First, spider genes were identified and deciphered, programming the formation of threads of one structure or another. Today it concerns 14 species of spiders. Then American specialists from several research centers (each group independently) introduced these genes into bacteria, trying to get the desired proteins in solution.
Scientists at the Canadian biotechnology firm Nexia introduced such genes into mice, then switched to goats, and the goats began to give milk with the very protein that forms the web thread. In the summer of 1999, two African pygmy goats, Peter and Webster, were genetically programmed to produce offspring of goats whose milk contained this protein. This breed is good because the offspring becomes adults already at the age of three months. The company is still silent on how to make threads from milk, but has already registered the name of the new material it created - “BioSteel” (“biosteel”). An article about the properties of "bio-steel" was published in the journal "Science" ("Nauka", 2002, vol. 295, p. 427).
German specialists from Gatersleben went the other way: they introduced spider-like genes into plants - potatoes and tobacco. They managed to obtain up to 2% of soluble proteins in potato tubers and tobacco leaves, consisting mainly of spidroin (the main fibroin of spiders). It is assumed that when the quantities of spidroin produced become significant, medical bandages will be made from it in the first place.
Milk obtained from genetically modified goats can hardly be distinguished by taste from natural. Genetically modified potatoes are similar to ordinary ones: in principle, they can also be boiled and fried.
IN different countries biotech companies have learned how to make artificial analogues of the web, but they are still far from the perfection of a natural polymer. It can be achieved only by understanding which of the physical or chemical features of the structure are responsible for the unique mechanical properties of the web, and success in solving an applied problem directly depends on the results of fundamental research.
Since 2007, a group of researchers from the Department of Bioengineering of the Faculty of Biology has joined this work Moscow State University M.V. Lomonosov under the guidance of Doctor of Physical and Mathematical Sciences, Professor K.V.Shaytana, and the results of their research have lifted the curtain on some of the secrets of this natural polymer.
But what about here biotechnology? Maybe cobwebs can be obtained naturally, like silk? Indeed, the production volumes of silk threads from cocoons woven by silkworm caterpillars are very significant. Indeed, such attempts were made, various devices were even invented for spider "milking" and the gentle winding of delicate threads on a slowly rotating spool (Debabov and Bogush, 1999; Work and Emerson, 1982).
There were several obstacles. Firstly, the quarrelsomeness of the spider nature: when kept together, these animals are at enmity and eat each other. Secondly, each spider produces very little web: it is estimated that 27 thousand spiders are required to produce 500 g of fiber medium size. It is clear that the productivity of arthropods is unlikely to meet industrial demands. There is only one way out: to learn how to get it artificially.
The 90s of the last century and the beginning of this century were marked by an increasing flow of research into the properties and structure of the web. Particularly great interest was shown in the UK, Germany, the USA and Japan. It was found that the web has a protein nature similar to silk. Spiders have several types of web glands and different types of webs:
- one - for the construction of cocoons, where females lay their eggs,
- the other is for parachuting, if you have to flee,
- adhesive - for the construction of the trapping part of the web,
- frame - on which it is superimposed.
The strongest web - frame, and it has been studied better than others. It is dominated by two proteins, called spidroin(from the English spider - spider). They are very long - each contains 2.5-3 thousand amino acid residues.
One of the scaffold proteins Orb weaving spider Nephila clavipes, widespread in the southern United States, with a trapping net up to a meter in diameter, was called spidroin-1, another - spidroin-2. The first is slightly shorter than the second: the molecular weight of spidroin-1 is 275 thousand atomic mass units, spidroin-2 is 320.
In different species of spiders, these proteins differ somewhat both in size - from 180 to 720 thousand a.m.u., and in the amino acid sequence, but they all have a common feature - the repetition of identical or almost identical amino acid sequences, including a section of several residues in a row alanine (usually four to nine) and an area with frequent repetition of glycine residues.
The physicochemical properties of proteins are determined by the characteristics of amino acid sequences, and spidroins are no exception. A unique property of spidroins is the alternation of segments rich in glycine and alanine. It determines how a molecule is folded in space, how several molecules are folded into fiber-fibril and ordered packing of such fibrils into nanofibrils cobweb fibers, and, in addition, at the ends of the molecules there are special groups of several tens of amino acids with hydrophilic properties.
Thanks to the significant efforts thrown into the study of all these levels of spatial organization of web proteins, much has become clear, although it is not yet completely clear.
First, main question: due to which remarkable mechanical properties of the web are achieved?
Studies using X-ray diffraction analysis (Warwicker, 1960; Glisovic and Salditt, 2007) showed that in the secretion of the arachnoid gland, the filaments of several protein molecules form many dense packs of 2 × 5 × 7 nm. It is believed that these are closely spaced alanine regions. Such structures are called β-layers. Many researchers of spider silk believe that the web owes its strength to them, and fragments rich in glycine coil into spirals and provide elasticity (Simmons et al., 1994; Parkhe et al., 1997, van Beek et. al, 2002 and others .).
To better understand the processes occurring at the molecular level, biologists from Moscow University turned to computer simulation. It allows in a numerical experiment, based on data on the structure of molecules and on the energy of interatomic interactions, to determine such properties of molecules as extensibility and tensile strength, to observe how molecules interact with each other - in a full-scale experiment this is extremely difficult, if at all achievable. Numerical experiments were carried out using supercomputer technologies.
“Using the example of spider web peptides, we were able to show that the stability of the secondary structure depends not only on the amino acid sequence, but also on the molecular environment,” says the author of the study. I. Orshansky. “Complexes of several peptides have a more stable secondary structure for both polyalanine peptides and interalanine peptides.”
And yet it remains a mystery: what causes the liquid secret to turn into a wonderful strong thread - solid and insoluble?
If this could be known in all details, there would be a key to reproducing this process, and hence to artificially obtaining a thread with the same qualities. In addition, the spider does it quickly, which means that high performance can be achieved.
It is now known (Scheibel et al., 2009) that in the process of “maturing” of the web before leaving the spider gland, the solution of spidroins undergoes many changes: the spider tissues extract water from it, due to which the concentration of proteins increases, ions of sodium and chlorine, but the content of potassium, phosphate ions and hydrogen increases, while the reaction of the medium decreases from 6.9 to 6.3 and becomes somewhat more acidic.
As a result of all these and other, not yet taken into account, processes, the protein rapidly changes its configuration. And, what is most remarkable, this happens at ordinary temperature and pressure and without the use of toxic reagents, which, for example, have to be used in the production of other synthetic polymers, in particular, Kevlar, and without toxic waste. It is also known that the tension of the released thread affects its strength: if a fresh thread is stretched with force, the web is thinner and stronger.
To date, some progress has been made in obtaining an artificial web. Early 90s. American researchers cloned in cells Escherichia coli spidroin genes that make up the warp thread of the spider Nephila clavipes. It became possible, using genetic engineering techniques, to insert fragments of spidroin genes into the genomes of other organisms and isolate from them a protein synthesized in vivo.
For such purposes, the same bacterium Echerichia coli is often used, but this technology is not suitable for spidroins: for bacteria, their molecules are too large, so biotechnologists turned their eyes to larger organisms.
IN Germany managed to implant the orb weaver genes into the genomes of potatoes and tobacco, and the yield of spidroin amounted to 2% of the total protein mass of these plants.
IN Japanese Shinsu University inserted a spidroin gene into the genome of the silkworm Bombyx mori, now their caterpillars produce a fiber composed of 10% cobweb proteins.
Canadian The biotech firm Nexia reported the successful introduction of the spidroin gene first into hamsters and then into goats, as a result of which proteins can be isolated from their milk, albeit in very small quantities. But most often, incl. in Russian biotechnological laboratories, for these purposes they use yeast - Pichia pastoris, which oxidizes methane, and beer yeast - Saccharomices cerevisiae.
IN Russia recognized leader in the production of artificial spidroins — State Research Institute of Genetics and Selection of Industrial Microorganisms(GosNIIgenetika). Since 2001, a scientific group led by Academician Russian Academy of Agricultural Sciences, Corresponding Member of the Russian Academy of Sciences, Professor V.G.Debabova develops methods for the production of recombinant spidroins.
From the known nucleotide sequence of the cDNA of the orb-web spider Nephila clavipes, biotechnologists selected several typical regions, synthesized the corresponding genes and inserted them into the yeast genome. The solution prepared from the isolated protein is “spun”, releasing through the thinnest hole into concentrated ethyl alcohol, where it turns into a fiber.
Their counterpart from Institute of Bioorganic Chemistry RAS D.V. Klinov developed a method for obtaining films of different thicknesses from a solution by electrospraying. By adjusting the protein content of the initial solution and the concentration of alcohol, and changing the course of subsequent processing, which includes drawing in alcohol, soaking in water and hot drying, the researchers are trying to choose the conditions for creating the most durable and elastic fiber.
Working with an artificial web has not only applied, but also fundamental scientific meaning.
“This problem is at the intersection of biology, protein engineering and materials science,” says K.V. Satan. “Understanding how the amino acid sequence affects the properties of a nanofiber will pave the way for the artificial creation of nanofibrils with given capabilities.”
Specialists from the Department of Bioengineering, Faculty of Biology, Moscow State University, together with colleagues from the State Research Institute of Genetics and Institute of Transplantology and Artificial Organs The Ministry of Health and Social Development of the Russian Federation is studying the properties of the thread on different stages processing it to unravel the mysteries of its secondary, tertiary, and quaternary structure (Bougush et al., 2008).
Examining the surface and fractures of a fresh, untreated artificial filament—a kind of analogue of the mature spinning solution in a spider gland—under a scanning electron microscope, they discovered that the filament was actually a hollow tube of spongy material punctured with many spherical holes 0.15 in diameter. -1 micron, and in the thickness of the solid material there are protein globules of the same size. Smaller globules 50–250 nm in size are found on the surface of the filaments in some processing options.
Scientists drew attention to the fact that formations of the same shape and size are also found in the spinning solution of spiders - maybe these are the same micelles on which the Americans' hypothesis is based? But the fragments of spidroins synthesized at the State Research Institute of Genetics are devoid of specific terminal fragments characteristic of natural spidroins! This means that the way molecules are packed into micelles is different from what was assumed in the existing hypotheses.
If a thread from recombinant spidroin is stretched before being removed from alcohol - this is considered as an analogy for a spider spinning a natural web - then its structure will change: thin fibrils with a diameter of 200-900 nm appear, they can be seen with an atomic force microscope. The natural web also has microfibrils However, they are ten times thinner.
On closer examination, thin fibrils turned out to be more like beads: thickening and thinner sections alternate in them. Under a transmission electron microscope, which makes it possible to examine the object through transmission and at higher magnification, inclusions 10–15 nm in diameter were found inside microfibrils, which are grouped into longitudinal structures up to 250 nm long. There is reason to believe that these are clusters of the same nanofibrils, which provide the unique mechanical properties of the natural web.
E. Krasnova, candidate of biological sciences
Durable materials have a wide range of uses. There is not only the hardest metal, but also the hardest and strongest wood, as well as the strongest man-made materials.
Where are the most durable materials used?
Heavy-duty materials are used in many areas of life. So, chemists in Ireland and America have developed a technology by which durable textile fibers are produced. The thread of this material is fifty micrometers in diameter. It is created from tens of millions of nanotubes, which are bonded together with the help of a polymer.The tensile strength of this electrically conductive fiber is three times higher than the strength of the web of the orb-weaving spider. The resulting material is used to make ultra-light body armor and sports equipment. The name of another durable material is ONNEX, created by order of the US Department of Defense. In addition to its use in the production of bulletproof vests, the new material can also be used in flight control systems, sensors, and engines.
There is a technology developed by scientists, thanks to which durable, hard, transparent and light materials are obtained by converting aerogels. On their basis, it is possible to produce lightweight body armor, armor for tanks and durable building materials.
Novosibirsk scientists have invented a plasma reactor of a new principle, thanks to which it is possible to produce nanotubulene, a heavy-duty artificial material. This material was discovered twenty years ago. It is a mass of elastic consistency. It consists of plexuses that cannot be seen with the naked eye. The thickness of the walls of these plexuses is one atom.
The fact that the atoms are sort of nested into each other according to the “Russian nesting doll” principle makes nanotubule the most durable material known. When this material is added to concrete, metal, plastic, their strength and electrical conductivity are significantly enhanced. Nanotubulene will help make cars and planes more durable. If the new material comes into wide production, then roads, houses, and equipment can become very durable. It will be very difficult to destroy them. Nanotubulene has not yet been introduced into widespread production due to the very high cost. However, Novosibirsk scientists managed to significantly reduce the cost of this material. Now nanotubulene can be produced not in kilograms, but in tons.
The hardest metal
Among all known metals, chromium is the hardest, but its hardness depends largely on its purity. Its properties are corrosion resistance, heat resistance and refractoriness. Chrome is a whitish-blue metal. Its Brinell hardness is 70-90 kgf/cm2. The melting point of the hardest metal is one thousand nine hundred and seven degrees Celsius at a density of seven thousand two hundred kg / m3. This metal is found in the earth's crust in the amount of 0.02 percent, which is quite a lot. It is usually found as chromium ironstone. Chromium is mined from silicate rocks. 
This metal is used in industry, smelting chromium steel, nichrome and so on. It is used for anti-corrosion and decorative coatings. Chromium is very rich in stone meteorites falling to Earth.
The most durable tree
There is wood that is stronger than cast iron and can be compared with the strength of iron. We are talking about "Schmidt's Birch". It is also called the Iron Birch. Man does not know a more durable tree than this. It was opened by a Russian botanist named Schmidt, while in the Far East. 
Wood exceeds the strength of cast iron by one and a half times, the bending strength is approximately equal to the strength of iron. Due to such properties, iron birch could well sometimes replace metal, because this wood is not subject to corrosion and decay. The ship's hull, made of Iron birch, can not even be painted, the ship will not be destroyed by corrosion, the action of acids is also not afraid of it.
Schmidt's birch cannot be pierced by a bullet, you cannot cut it down with an ax. Of all the birches on our planet, it is the Iron Birch that is long-lived - it lives for four hundred years. Its place of growth is the Kedrovaya Pad Nature Reserve. This is a rare protected species, which is listed in the Red Book. If not for such a rarity, the heavy-duty wood of this tree could be used everywhere.
But the tallest trees in the world, sequoias, are not very durable material.
The strongest material in the universe
Graphene is the strongest and at the same time lightest material in our universe. This is a carbon plate, which is only one atom thick, but it is stronger than diamond, and the electrical conductivity is a hundred times higher than the silicon of computer chips. 
Soon graphene will leave scientific laboratories. All the scientists of the world talk today about its unique properties. So, a few grams of material will be enough to cover an entire football field. Graphene is very flexible, it can be folded, bent, rolled up.
Possible areas of its use are solar panels, cell phones, touch screens, super-fast computer chips.
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