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According to modern ideas, life as we know it was preceded by the world of RNA molecules. This concept was created by an outstanding scientist, one of the founding fathers of molecular biology, Academician A. S. Spirin.
The three main biopolymers that make up life are DNA, RNA, and proteins. DNA stores genetic information, it's like a safe. We got a good variant and translated it into the form of DNA, where it remains unchanged for many generations. In this series, RNA is a unique molecule. Like DNA, it carries genetic information, but it also evolves rapidly. RNA can serve as a template for the synthesis of protein, DNA, and itself. Unlike DNA and proteins, RNA is self-sufficient. In 1982, it was discovered that it could catalyze, or accelerate, biochemical reactions. In 2000, it was established that it is RNA that catalyzes the reactions of peptide bond formation that lead to the synthesis of proteins. Then it became obvious to Alexander Sergeyevich Spirin that life originated in the form of RNA, and he began to develop his concept.
"It is believed that an Englishman was the first to write about it, in 1968, Francis Creek and American Leslie Orgel, one of the discoverers of the DNA double helix. However, 11 years earlier, the same idea had been expressed by the Soviet biochemist, Spirin's teacher, Academician Andrei Nikolayevich Belozersky. And although it was at an international symposium on the origin of life, the West did not notice it.
Spirin developed the idea into a concept, relying on our developments.
«
"It seems that RNA, which is associated with the most common manifestations of life, was formed at an earlier stage in the development of life, while the emergence of DNA is associated with the formation of narrower and phylogenetically later properties of organisms." (A. N. Belozersky, Moscow International Symposium "The Origin of Life on Earth", 1957)
To begin with, we need nucleotides (organic compounds that make up RNA, DNA. – Ed.). They could be synthesized spontaneously, for example, during lightning discharges in an anoxic atmosphere. In 1992, it was found that modified nucleotides are able to combine themselves into short oligonucleotides. Then, we're in Pushchino discovered that spontaneous (spontaneous) recombination is possible between RNA molecules, leading to their unification and exchange of regions. Spearin theorized that this reaction was the primary mode of RNA molecules. By spontaneous recombination, short oligonucleotides joined together into long RNA molecules.
But in order for randomly generated RNA molecules to produce offspring, they need to be replicated, i.e., copied according to the principle of complementarity.
Spirin proposed such a mechanism. A long matrix was formed, and a complementary chain was assembled from short oligonucleotides by means of the spontaneous unification reactions we discovered. But there's a problem. As a result, a two-stranded (double-stranded) molecule was formed, which, like DNA, is a double helix. However, such RNA is inert, and all its coding valences are occupied. Therefore, it cannot serve as a matrix. You need a single-stranded molecule. This means that double-stranded RNA must be unraveled into its component strands. Spirin concluded that a molecular machine was indispensable.
"What kind of molecular machine is this?"
"Spirin came up with the idea of molecular machines by studying ribosomes, cellular particles that synthesize proteins. They consist of two halves – small and large subparticles. According to the model proposed by Spirin back in 1968, each cycle of building up a polypeptide chain with a new amino acid is accompanied by the opening and closing of these halves and the movement of the ribosome along the messenger RNA by one triplet or three nucleotides encoding this amino acid. But the ribosome is a huge particle with a mass of about three million daltons. For comparison, a water molecule is 18 daltons. What makes this "machine" work? What kind of fuel does it have?
It was assumed that it was GTP (guanosine triphosphate), which is consumed by the ribosome in a similar way to ATP (adenosine triphosphate) during muscle contraction. However, it turned out that the ribosome works without GTP, only more slowly.
The only available source of energy is the thermal (Brownian) motion of solvent molecules, mainly water, bombarding the ribosome. Moreover, it turned out that the total power received by the ribosome from these impacts is billions of times greater than what comes from GTP. But such blows are chaotic, only a part of them is useful. This means that we need some kind of Feynman "ratchet" that "filters" the shocks and ensures the movement of the ribosome along the messenger RNA in a certain direction.
Spirin showed that the synthesis of the polypeptide itself acts as such a ratchet. It is an irreversible unidirectional process. You can compare it to a traffic controller at an intersection.
In principle, this problem can be solved in another way. For example, in the well-known PCR (polymerase chain reaction – Ed.) process, which is widely used, in particular, to diagnose infections, periodic changes in temperature help. At a relatively low temperature (50-60 degrees), DNA strands are copied, and at a high temperature (about 100 degrees), the resulting two-stranded molecules are unraveled, which guarantees the continuation of the DNA synthesis process in the next cycle.
Probably, on the cosmic body where the RNA world was born, there were the necessary diurnal temperature fluctuations, and this body itself was an analogue of a giant PCR machine. However, such a machine worked very slowly - one cycle per day. Further evolution required acceleration, and molecular machines were needed.
The first could be an RNA molecule capable of catalyzing the assembly of a strand that is complementary to the template, the prototype of modern RNA polymerase. As long as the primary RNA polymerase was small, it had to wait for the day to come and for the double-stranded RNAs it synthesized to unravel.
It should be noted here that a two-stranded DNA or RNA molecule unravels when the temperature rises due to an increase in the total power of the solvent molecules hitting it. This can be achieved not only by increasing the temperature, but also by increasing the size of the target.
As the RNA polymerase grew in size as a result of evolution, it began to evolve into a molecular machine capable of catching Brownian motion, as a sail catches the wind, and unraveling the associated two-stranded RNA. Gradually, the unraveling took place at a lower and lower temperature, and finally the entire process of RNA replication was possible at a constant temperature. The ratchet in this situation was the irreversible synthesis of the complementary chain.
The three main biopolymers that make up life are DNA, RNA, and proteins. DNA stores genetic information, it's like a safe. We got a good variant and translated it into the form of DNA, where it remains unchanged for many generations. In this series, RNA is a unique molecule. Like DNA, it carries genetic information, but it also evolves rapidly. RNA can serve as a template for the synthesis of protein, DNA, and itself. Unlike DNA and proteins, RNA is self-sufficient. In 1982, it was discovered that it could catalyze, or accelerate, biochemical reactions. In 2000, it was established that it is RNA that catalyzes the reactions of peptide bond formation that lead to the synthesis of proteins. Then it became obvious to Alexander Sergeyevich Spirin that life originated in the form of RNA, and he began to develop his concept.
"It is believed that an Englishman was the first to write about it, in 1968, Francis Creek and American Leslie Orgel, one of the discoverers of the DNA double helix. However, 11 years earlier, the same idea had been expressed by the Soviet biochemist, Spirin's teacher, Academician Andrei Nikolayevich Belozersky. And although it was at an international symposium on the origin of life, the West did not notice it.
Spirin developed the idea into a concept, relying on our developments.
«
"It seems that RNA, which is associated with the most common manifestations of life, was formed at an earlier stage in the development of life, while the emergence of DNA is associated with the formation of narrower and phylogenetically later properties of organisms." (A. N. Belozersky, Moscow International Symposium "The Origin of Life on Earth", 1957)
To begin with, we need nucleotides (organic compounds that make up RNA, DNA. – Ed.). They could be synthesized spontaneously, for example, during lightning discharges in an anoxic atmosphere. In 1992, it was found that modified nucleotides are able to combine themselves into short oligonucleotides. Then, we're in Pushchino discovered that spontaneous (spontaneous) recombination is possible between RNA molecules, leading to their unification and exchange of regions. Spearin theorized that this reaction was the primary mode of RNA molecules. By spontaneous recombination, short oligonucleotides joined together into long RNA molecules.
But in order for randomly generated RNA molecules to produce offspring, they need to be replicated, i.e., copied according to the principle of complementarity.
Spirin proposed such a mechanism. A long matrix was formed, and a complementary chain was assembled from short oligonucleotides by means of the spontaneous unification reactions we discovered. But there's a problem. As a result, a two-stranded (double-stranded) molecule was formed, which, like DNA, is a double helix. However, such RNA is inert, and all its coding valences are occupied. Therefore, it cannot serve as a matrix. You need a single-stranded molecule. This means that double-stranded RNA must be unraveled into its component strands. Spirin concluded that a molecular machine was indispensable.
"What kind of molecular machine is this?"
"Spirin came up with the idea of molecular machines by studying ribosomes, cellular particles that synthesize proteins. They consist of two halves – small and large subparticles. According to the model proposed by Spirin back in 1968, each cycle of building up a polypeptide chain with a new amino acid is accompanied by the opening and closing of these halves and the movement of the ribosome along the messenger RNA by one triplet or three nucleotides encoding this amino acid. But the ribosome is a huge particle with a mass of about three million daltons. For comparison, a water molecule is 18 daltons. What makes this "machine" work? What kind of fuel does it have?
It was assumed that it was GTP (guanosine triphosphate), which is consumed by the ribosome in a similar way to ATP (adenosine triphosphate) during muscle contraction. However, it turned out that the ribosome works without GTP, only more slowly.
The only available source of energy is the thermal (Brownian) motion of solvent molecules, mainly water, bombarding the ribosome. Moreover, it turned out that the total power received by the ribosome from these impacts is billions of times greater than what comes from GTP. But such blows are chaotic, only a part of them is useful. This means that we need some kind of Feynman "ratchet" that "filters" the shocks and ensures the movement of the ribosome along the messenger RNA in a certain direction.
Spirin showed that the synthesis of the polypeptide itself acts as such a ratchet. It is an irreversible unidirectional process. You can compare it to a traffic controller at an intersection.
In principle, this problem can be solved in another way. For example, in the well-known PCR (polymerase chain reaction – Ed.) process, which is widely used, in particular, to diagnose infections, periodic changes in temperature help. At a relatively low temperature (50-60 degrees), DNA strands are copied, and at a high temperature (about 100 degrees), the resulting two-stranded molecules are unraveled, which guarantees the continuation of the DNA synthesis process in the next cycle.
Probably, on the cosmic body where the RNA world was born, there were the necessary diurnal temperature fluctuations, and this body itself was an analogue of a giant PCR machine. However, such a machine worked very slowly - one cycle per day. Further evolution required acceleration, and molecular machines were needed.
The first could be an RNA molecule capable of catalyzing the assembly of a strand that is complementary to the template, the prototype of modern RNA polymerase. As long as the primary RNA polymerase was small, it had to wait for the day to come and for the double-stranded RNAs it synthesized to unravel.
It should be noted here that a two-stranded DNA or RNA molecule unravels when the temperature rises due to an increase in the total power of the solvent molecules hitting it. This can be achieved not only by increasing the temperature, but also by increasing the size of the target.
As the RNA polymerase grew in size as a result of evolution, it began to evolve into a molecular machine capable of catching Brownian motion, as a sail catches the wind, and unraveling the associated two-stranded RNA. Gradually, the unraveling took place at a lower and lower temperature, and finally the entire process of RNA replication was possible at a constant temperature. The ratchet in this situation was the irreversible synthesis of the complementary chain.
