G.Cragnolini I.T.I. Malignani - Udine THE PUZZLE OF A LIQUID ROPE

G.Cragnolini I.T.I. Malignani - Udine

THE PUZZLETHE PUZZLEOF OF A LIQUID A LIQUID ROPEROPE


the transformation from a liquid to a solid the transformation from a liquid to a solid phase is never trivial; phase is never trivial;

imagine the cooling of a lava stream or imagine the cooling of a lava stream or the delicate crystal lattice of frozen water, the delicate crystal lattice of frozen water, where each crystal is different;where each crystal is different;

solidification processes can be useful or even solidification processes can be useful or even lethal (e.g. blood coagulation in-or outside veins);lethal (e.g. blood coagulation in-or outside veins);

however, if done by spiders , the solidification however, if done by spiders , the solidification process is simply amazing;process is simply amazing;


most people ignore most people ignore that spiders, often not that spiders, often not greater than a pea, greater than a pea, produce up to 2000 feet produce up to 2000 feet of thread continuously; of thread continuously;

where the hell where the hell

do they store it ???do they store it ???


The question involves a solidification process;The question involves a solidification process;in general, solidification is due :in general, solidification is due :

-- to temperature drop, as in water freezing; -- to temperature drop, as in water freezing; -- to solvent evaporation, like sodium chloride-- to solvent evaporation, like sodium chloride in salt works ;in salt works ;

nevertheless, none of these models is fit to explain nevertheless, none of these models is fit to explain the instantaneous solidification of the thread made the instantaneous solidification of the thread made up by spiders ;up by spiders ;

the answer is that spider’s long, silky string comes the answer is that spider’s long, silky string comes from the solidification of a liquid;from the solidification of a liquid;


But :But :--- spiders live at room temperature, --- spiders live at room temperature, thereby excluding all freezing processes;thereby excluding all freezing processes;

--- the only solvent found inside spiders is --- the only solvent found inside spiders is water, but water evaporates slowly at water, but water evaporates slowly at room temperature, while spider’s thread room temperature, while spider’s thread solidifies immediately ( it holds the mass solidifies immediately ( it holds the mass of the insect as soon as produced ); of the insect as soon as produced );

--- besides, if the thread was soluble in water, --- besides, if the thread was soluble in water, then it would be dissolved by rain or dew;then it would be dissolved by rain or dew;

--- ---


so, what remains ?so, what remains ?

The last chance is a kind of polymerisation The last chance is a kind of polymerisation process, as for nylon ;process, as for nylon ;

unfortunately nylon melts over 250 °C , that is unfortunately nylon melts over 250 °C , that is much higher than every survival limit; much higher than every survival limit; moreover, polymerisation processes are slow;moreover, polymerisation processes are slow;

anyway, a quick look at polymers may help us anyway, a quick look at polymers may help us understand spiders’ work :understand spiders’ work :


polymers are buildings with molecular polymers are buildings with molecular weights of thousand hundreds ; weights of thousand hundreds ;

atoms that make up the backbone of a atoms that make up the backbone of a polymer chain come in a regular order; polymer chain come in a regular order;

this pattern is reproduced all along the length this pattern is reproduced all along the length of the chain. of the chain.

the little recurring structures are called the little recurring structures are called “ “ monomers “ ;monomers “ ;




most of polymers are linear, that is joined in a long most of polymers are linear, that is joined in a long line to form a huge and flexible chain, often bent in a line to form a huge and flexible chain, often bent in a tangled mess; tangled mess;

when molten, these chains will act like elastic cooking when molten, these chains will act like elastic cooking “spaghetti” , while cooled in the solid state, they look “spaghetti” , while cooled in the solid state, they look more like a ball of string; more like a ball of string;

all molecules, the small ones as well as the polymer all molecules, the small ones as well as the polymer chains, interact sticking together through forces chains, interact sticking together through forces placed on the backbone;placed on the backbone;


when tangled in a ball, polymers set out when tangled in a ball, polymers set out a little number of binding forces; when a little number of binding forces; when stretched, many more of them appear and stretched, many more of them appear and work:work:


the yield of spiders the yield of spiders has a variable has a variable composition based on composition based on the amino – acids sequence :the amino – acids sequence :

…… …… ala-ala-gly-ala-ala-gly- ala-ala …..ala-ala-gly-ala-ala-gly- ala-ala …..


finally the enigma is puzzled out; finally the enigma is puzzled out; the solution is unbelievably simple, the solution is unbelievably simple, as it often happens in nature: as it often happens in nature:

spiders excrete a sticky fluid spiders excrete a sticky fluid containing long protein molecules containing long protein molecules tangled as a thread ball ;tangled as a thread ball ;

each chain, when stressed, shows many each chain, when stressed, shows many chemical structures fit to stick molecules chemical structures fit to stick molecules together , the same way polymers do ; together , the same way polymers do ;


this way, stretched molecules can join other this way, stretched molecules can join other ones to form a solid thread;ones to form a solid thread;

this is the reason why spiders excrete only this is the reason why spiders excrete only in conditions of traction;in conditions of traction;

in other words, the protein fluid is drawn in other words, the protein fluid is drawn out only in presence of an external force, out only in presence of an external force, such as wind or gravity ;such as wind or gravity ;


alalthough hard to agree to, spider’s though hard to agree to, spider’s filament is one of the strongest filament is one of the strongest materials in the world (more than materials in the world (more than steel) and highly elastic at the same steel) and highly elastic at the same time :time :

tensile strength can withstand a weight tensile strength can withstand a weight of up to 300.000 pounds per square inch of up to 300.000 pounds per square inch ( Nexia Biotechnologies - Montreal ) ;( Nexia Biotechnologies - Montreal ) ;


What about copying spider’s silk ???What about copying spider’s silk ???

--- bridge suspension cables could be modelled --- bridge suspension cables could be modelled on its molecular structure;on its molecular structure;

--- car bumpers and bullet-proof vests that --- car bumpers and bullet-proof vests that absorb impacts as the spider’s web does;absorb impacts as the spider’s web does;

--- flexible and resistant material for aircraft ......--- flexible and resistant material for aircraft ......


unfortunately, spider farms are not unfortunately, spider farms are not possible because spiders tend possible because spiders tend to eat one another; to eat one another;

therefore, to get this surprising material therefore, to get this surprising material (five times stronger than steel and more (five times stronger than steel and more elastic than kevlar ), only industrial elastic than kevlar ), only industrial processes can be used;processes can be used;


THIS PROVES AGAIN THAT CHEMISTS THIS PROVES AGAIN THAT CHEMISTS ARE ABSOLUTELY NECESSARY;ARE ABSOLUTELY NECESSARY;

spider’s secret being now unveiled, let’s have spider’s secret being now unveiled, let’s have a little gossip :a little gossip :


..... Arachne, a pretty maid of ..... Arachne, a pretty maid of ancient Greece woved ancient Greece woved tapestries of such a beauty that tapestries of such a beauty that goddess Athena, who fancied goddess Athena, who fancied herself superior to any girl , herself superior to any girl , became furious and turned became furious and turned Arachne into a spider ; Arachne into a spider ;

now she is living among gods, now she is living among gods, but is convicted to spin for but is convicted to spin for eternity .......eternity .......


..... natives from the Pacific, ..... natives from the Pacific, Asia and Australia used Asia and Australia used spider silk to weave water spider silk to weave water shedding rain gear, make shedding rain gear, make fishing lines and construct fishing lines and construct nets; nets;

..... Gengis khan and his soldiers wore a ..... Gengis khan and his soldiers wore a leather garment interwoven with spider leather garment interwoven with spider silk, to protect them from enemy arrows;silk, to protect them from enemy arrows;


o.k., that’s all; o.k., that’s all;

by the way, aby the way, a thankful acknowledgement to thankful acknowledgement to all members of the team :all members of the team :

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G.Cragnolini I.T.I. Malignani - Udine THE PUZZLE OF A LIQUID ROPE