- Serie «CrowdScience»
- BBC World Service
Have you ever wondered, maybe when you’re already desperate trying to undo a stubborn knot, why things get tangled up instead of behaving the way we need them to?
No matter how careful you are, things like smartphone headphones, the hose with which you water the garden plants, the hair dryer cables … even the hair itself demands our attention sometimes at times when it is difficult to give it. .
Perhaps to console ourselves we can turn to science and avail ourselves of Second law of thermodynamics which states that all closed systems tend to maximize entropy, a measure of disorder.
The Universe, in short, tends to chaos.
But if that doesn’t satisfy you, tangles may no longer be so annoying if, when you are unraveling them, you keep in mind that they are essential to life … literally: are in the DNA.
Let us remember in advance that not all knots are the same. Some can be incredibly helpful in saving lives.
Although today most of us were only taught to tie our shoelaces, in the past we learned multiple knots. it was an indispensable skill.
Knots are in fact a technology that our ancestors discovered before the wheel. Without them, you cannot weave cloth or tie a head of flint on a stick.
And while it is true that in modern life there is not much need to make your own spears, for certain groups, such as fishermen, sailors, surgeons or tailors, it is still crucial to know how to tangle its strings.
However, even they probably come up against awkward knots from time to time… why do they appear when you don’t want them?
Well, there is a scientist who looked for answers.
Doug Smith is a professor of physics at the University of California, San Diego. A few years ago, he did a deceptively simple experiment with one of his undergraduate students.
The study earned him a Ig Nobel, an award given to science that makes you laugh, and then makes you think.
He wanted to understand why knots formed spontaneously and, following the scientific method, they dropped pieces of rope of different kinds into a box that was stirred by a motor.
About 3,000 times later, they found that “the longer and more flexible the rope, the more likely it is that knots will form,” which is why, no matter how hard you try, it’s almost guaranteed that when you take your headphone cables out of your bag or the Christmas lights out of the box you stored them in last year, they’re going to be tangled.
And something that worsens the situation is torsion, according to the RAE, “action and effect of twisting or twisting something in a helical way.”
That is, take a cable that you have on hand and hold it stretched out with your fingers at two points. Begins to twist one end; you will see that it undulates and even forms a side branch.
“When twist is introduced into cables, even unintentionally, the energy is converted and causes them to bend. And it is very difficult to prevent that from happening.
“The more it twists, the more impossible to untangle,” explains Smith.
One of the reasons all this happens sounds like a life lesson: “there is little chance that everything remains as it should be, but a thousand ways to make a mess«.
It is the natural order of things. Or rather, the natural disorder of things.
But if it’s about nature, then nature has a problem.
In fact, life as we know it has a problem, because all the important information that keeps our bodies working in every cell of our being is in our DNA … which looks like those old telephone cords that were sometimes a nightmare.
Are we hopelessly entangled at the molecular level?
DNA is a very long string that resides in a very small space. If you took it out and stretched it out, it would measure 2 meters.
Imagine that packed into a cell so small it can’t be seen without a microscope, and you can probably imagine its potential for entanglement.
However, the bodies have some trick to prevent it from happening and that is what Mariel Vazquez investigated: how the chain like DNA tangles and unravels, is knotted and untied throughout its life cycle.
Let’s go back to that wire we had twisted. The first thing that was formed was something that looks like the famous double helix of the so-called molecule of life.
With more twist, it rolls up on itself.
“DNA does exactly the same thing,” says University of California Davis professor, an expert in mathematics combined with microbiology and molecular biology.
“We call it the supercoil.”
What we do not want that to happen with our cables, is crucial to the way cells package DNA.
But in order to fit perfectly inside the cell, DNA has to do more. It has to wrap itself around “proteins called histones, which form like a string of pearls.”
“The DNA wraps itself a couple of times around each histone and goes on to the other.”
However, it is not enough, so that pearl necklace is twisted on itself multiple times until, eventually, “the DNA is very, very well packed and condensed.”
The problem is that, just as sometimes you need to take out and use the things that you so carefully ordered and stored, each time your body generates a new cell, which it constantly does, your DNA needs to be copied and that implies that it must be disarranged.
Not only that: the two propellers have to be separated.
This is where biology has a very clever trick: molecular scissors. What holds the two strands of DNA together are hydrogen bonds. The scissors are really enzymes, special types of protein that cut through the helix in a very controlled way, ”explains Vazquez.
“Once separated, the machinery of the cell begins to create the two new strands of DNA.”
But that is when we find the family problem. The two strands of DNA they are uselessly tangled together.
It is easier to understand what happens by thinking about bacteria, which have a simple loop of DNA.
“When the DNA finishes copying, two interconnected circles remain but they have to be separated. The cell again uses the molecular scissors to very carefully and gently cut one of the circles, let the other go through and reseal the rupture. ‘
That happens billions and billions of times, and understanding it allowed to create medicines.
“There are antibiotics that when they enter your body, they deactivate that molecular machine of the bacteria, so that their DNA becomes completely entangled and the bacteria die.”
Beyond the area of medicine, scientists from many fields have been trying to take advantage of the properties of knots and tangles.
One of them is David Lee, professor of chemistry at the University of Manchester, who with his team is dedicated to studying supreme miniaturization and molecular knotting and weaving.
It knots “very, very small and they have eight crosses, so they are very complicated. It is the tightest physical structure ever bound on this planet.«.
One that gave him one of his two world records: the tightest knot in the world and the most finely woven fabric.
It may be a fun challenge, but why do it?
«The knots are omnipresent in the molecular world, and nature uses them because it has found ways to take advantage of their useful functions, something that we can learn ‘, to do things like improve materials that are used in technology.
And those nano-sized knots can be turned into nets or meshes with incredible properties.
“Tangling threads by controlling the crossing pattern” – that is, weaving – “can not only make the fabric stronger, but its gaps can allow the beneficial to pass through and trap the unwanted.”
Because its threads are molecular, these meshes could block “large molecules, or bacteria, or maybe even viruses.”
In short, without the option to tie and untie knots, we would not exist. And even if you put that detail aside, our lives would be more uncomfortable: imagine a world without pillows, clothes, or blankets.
Luckily knots are unavoidable and, as the Ig Nobel laureate demonstrated, occur naturally wherever there is something long and thinWhether it’s a long DNA molecule, the cables in your devices, or the hair you pull when you can’t undo them.
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