Louis Pasteur was a brilliant chemist who stumbled upon an interesting phenomenon related to crystals in 1848 while studying industrial winemaking. In the process, he accidentally observed these crystals. Interestingly, although half of these crystals can easily be identified as tartaric acid, the other half exhibits precise shape and symmetry, and some of them are oriented in opposite directions.
The difference was so significant that Pasteur was able to separate the crystals using a magnifying glass and tweezers. In one of his essays, he likened their relationship to an image and its reflection in a mirror. Unbeknownst to Pasteur at the time, in the crystallized residues of wine, he had stumbled upon a profound secret related to the origin of life on Earth. He observed that tartaric acid molecules have the same atomic composition but are mirrored in space. This property came to be called"Chirality", of Greek origin"hands"The term is used to describe how the left and right hands of the tartaric acid molecule are different and not interchangeable, just as our left and right hands are symmetrical opposites.
Pasteur's observation is of great significance, not only because of his discovery of chiral phenomena, but also for profound reasons. During the boiling process, both left- and right-handed tartaric acid enantiomers are present in the man-made crystals, while the natural crystals from the barrel contain only d-tartaric acid. This distinction arises because the grapes used to make wine come from living vines that specialize in the production of an enantiomer. Chirality is what we understand as a sign of life. Biochemists have long observed that living cells use only one chirality when using chiral molecules. For example, sugars that make up DNA are completely dextrared, while amino acids that make up proteins are completely left-handed. When the wrong enantiomers enter the drug, their effects can sometimes be harmful or even fatal.
At some point in the history of early life, an event or series of events occurred, as described by biochemists, "breaking the mirror", leading to the asymmetry of molecules in life. Scientists have been carefully studying why life tends to have the same chirality – that is, chirality – and whether this transition is inevitable or purely accidental. They determined whether the preference for chirality in early life came from a selective set of molecules in space, or from a mixture that originally contained an equal number of left and right hand molecules.
Soumitraath**ale, an assistant professor of organic chemistry at UCLA, said: "This observation is baffling to scientists. Over the years, a wide variety of theories have been proposed, but it has always been a challenge to come up with ideas related to geology. "While many theories can explain the emergence of homogeneity in a single type of molecule, none can adequately explain why this is the case for the entire biomolecular network. Recently, a team of researchers at Harvard University published a series of ** proposing a fascinating hypothesis about the emergence of the homogeneity of life. They believe that in the primordial Earth's water bodies, the magnetic surface of the minerals was affected by the Earth's magnetic field and functioned as a "chiral medium". These minerals may selectively attract certain forms of molecules, initiating a process that expands the chirality of the biomolecule, starting with RNA precursors and extending to proteins and many more other molecules. The mechanism they propose sheds light on how preferences are propagated in some molecules, thus establishing a broad network of chiral chemistry that supports life.
Gerald Joyce, a biochemist and director at the Salk Institute, who was not involved in the study, said: "It's not the only idea that seems plausible, but it's one of the most fascinating, because it links geophysics, geochemistry, pre-life chemistry and, ultimately, biochemistry." Joyce appreciates the hypothesis tested by "real experiments". The origins of this new theory of homogeneity can be traced back to about 25 years ago, when ronnaaman, a professor of chemical physics at the Weizmann Institute of Science in Israel, and his team discovered a key role for chiral molecules. Their research delved into how electrons redistribute themselves when molecules interact with other molecules or surfaces, and these electrons have both a negative charge and a quantum property called "spin," similar to an intrinsic clockwise or counterclockwise rotation. This redistribution polarizes the molecules, creating a negative charge at their destination and a positive charge at their point of origin.
Naaman and his team found that chiral molecules are classified according to the spin direction of electrons. Electrons with specific spins are more likely to pass through chiral molecules in one direction but encounter more resistance in the other direction. Whereas, electrons with opposite spins produce the opposite effect. To understand this phenomenon, imagine throwing a frisbee and hitting a wall. If the disc spins clockwise and hits the wall on the right, it moves forward;Otherwise, it will be bounced back. If it hits the wall on the left, the opposite is true. Similarly, chiral molecules can "redirect electrons according to the spin direction", as Naaman explains. This phenomenon is known to Naaman and his team as chiral-induced spin-selectivity (CISS) effects.
Due to the reorientation of chiral molecules, electrons with a particular spin are clustered at one end of the chiral molecule, while electrons with opposite spins are gathered at the other end. This rearrangement affects how chiral molecules interact with magnetic surfaces. Electrons with opposite spins attract each other, while electrons with the same spin repel each other. Thus, when a chiral molecule is close to a magnetic surface, it will be pulled closer if it has an opposite spin preference to the magnetic surface. Conversely, if they rotate in the same direction, they push each other apart. However, due to the ongoing chemical reaction, the molecules cannot simply flip to rearrange themselves. As a result, magnetic surfaces can act as chiral reagents, selectively interacting with only one version of the compound.
In 2011, Naaman and his team collaborated with researchers at the University of Münster in Germany to conduct an experiment on the spin movement of electrons in double-stranded DNA. These experiments verified the substance and authenticity of the CISS effect. This discovery has sparked a great deal of interest in this effect and its potential applications. Naman mentioned that it was from this time that his team began to develop various ways to exploit the CIS effect, such as purifying biological drugs by removing impurities or excluding false enantiomers in the drug to avoid serious *** In addition, they also investigated how the CIS effect could reveal the principles behind the anesthesia mechanism.
They began their search for the CISS effect to promote biological homogeneity because of the reception of Harvard astronomer Dimittal Saserov and his graduate student S.Sfurkanozturk led the team of invites, inviting them to cooperate ** a hypothesis. Young lead author Ozturk, who ran into same-sex problems as a physics graduate student at Harvard University in 2020, was unhappy with his own research in quantum simulations using ultracold atoms. By chance, he discovered a scientific journal detailing the world's 125 largest mysteries and became interested in the concept of homogeneity. This also led to their research into the CISS effect.
Ozturk and Sasselov's idea stemmed from the brainstorming of the CIS effect. They envisioned a primitive scenario, similar to a shallow lake covered with magnetic minerals covering the surface, and the water contained a mixture of chiral precursors of nucleotides. According to their theory, ultraviolet light may have expelled many electrons from magnetic surfaces, many of which share the same spin. These ejected electrons may selectively interact with specific enantiomers, resulting in a chemical reaction that preferentially assembles the right-handed RNA precursor.
In April 2022, Ozturk traveled to Israel to visit Naaman's lab and couldn't wait to put their hypothesis into practice. However, his excitement was quickly dispelled. In a month of working with Naaman's team, the idea did not gain support. ozturk was disappointed and thought the idea"It doesn't work"。But then Ozturk rethought the question. What if the CISS effect was not a chemical process, but a physical one. Naaman's team has demonstrated the ability to separate chiral isomers using selective crystallization of magnetic surfaces. Crystallization appears to be the easiest way to purify enantiomers. Ozturk shared this perspective with John Sutherland, a partner at the MRC Molecular Biology Laboratory in the UK.
Sutherland became interested in the interesting aspects of crystallization because his team had previously discovered a special RNA precursor called riboaminooxazoline (RAO), which could be used to build two components of RNA. In addition, Rao has an amazing ability to form beautiful crystals. Once the seed is pulled from the chiral isomer to the surface for formation, the crystal preferentially binds to more identical chiral isomers and grows.
Ozturk vividly recalls Sutherland's words: "If the idea of the CIS effect succeeds, it will be a 'game over' moment." "Applying it to a molecule that is critical to the chemistry of the origin of life means that achieving homogeneity in that molecule can extend to the entire system." At the Harvard lab, Ozturk started the experiment. He introduced the surface of magnetite into a Petri dish, which was then injected with a solution containing equal amounts of left- and right-handed Rao molecules. He placed the Petri dish on a magnet and put the experiment in the freezer, anticipating the appearance of the initial crystals. Initially, 60% of the crystals exhibited unichiorality. After repeating this process, all crystals exhibited 100% chirality.
Their findings, published in the June issue of the journal Science Advances, reveal that by magnetizing surfaces in one direction, they produce only right-handed crystals. On the contrary, when the direction of magnetization is reversed, the crystal is completely left-handed.
Despite their success, a major obstacle remained: the magnets used in their experiments exceeded the strength of the Earth's magnetic field by about 6,500 times. To solve this problem, Ozturk revisited the Weizmann Institute of Science in November and collaborated with Naman on subsequent experiments, which did not use an external magnetic field. Instead, they found that when chiral molecules adhere to a magnetic surface, they create a strong local magnetic field on the surface, up to 50 times the strength of the Earth's magnetic field.
"You're actually pushing the magnetization of the surrounding area, which promotes crystals to form more smoothly," Joyce said. He added that this self-sustaining effect makes the situation credible. Assavalle agrees with this view, noting that the lack of a high magnetic field requirement for the CISS effect is significant, as it indicates the presence of an underlying geological setting. However, the key aspect of achieving homogeneity lies in understanding how this effect propagates in an interconnected molecular network. The key achievement, Sasselov emphasized, is not just finding another way to generate chiral products, but also finding a way to build same-sex chiral networks.
In the August issue of the Journal of Chemical Physics, Ozturk, Sasselov, and Sutherland published a striking article introducing a model that explains how chiral information travels through networks before the origin of life. In earlier studies, Sutherland's team showed right-handed spinning RNA molecules that are responsible for binding amino acids and guiding them to build proteins, linking to amino acids in the left hand 10 times faster than in the right hand. This finding implies that chiral RNAs tend to produce proteins with opposite chirality, which is similar to what is observed in nature. The researchers highlight that the challenge of biohomogeneity may revolve around ensuring that a single common RNA precursor, such as Rao, can become homogeneous chiral.
According to Ozturk, the study does not directly explain why life tends to use right-handed nucleotides and left-handed amino acids. However, recent findings suggest that the key determinant may be magnetization induced by the Earth's magnetic field. Assavel noted that even if crystallization occurs in 100 ancient lakes, the Earth's magnetic field will ensure consistency, producing the same precursors of the dominant hand, rather than mixing. Joyce makes an interesting point that highlights a potential twist: if the magnetic field creates a bias against chirality, then if life originated in the northern hemisphere, which is biased towards one hand, then if life originated in the southern hemisphere, it may exhibit opposite chiral Xi.
As Ath**Ale emphasizes, the transfer of chirality between different molecules is still speculative, but the concept is encouraging and can provoke thought. Sasselov agrees, saying that the purpose of this article is to motivate individuals to conduct these experiments. Ma Discovery, a researcher at the origin of life at Wuhan University, recently showed "interesting progress", but he noted that we need to observe the culmination of the CISS effect in RNA polymerization to consider this a comprehensive solution. He believes that achieving this outcome will bring us closer to a solution.
Astrophysicist Globus mentions that "I find the CISS effect very interesting" and that she is working on the problem of homogeneity. To support this idea, she suggested that researchers investigate whether meteorites carrying large amounts of amino acids also exhibit excess magnetic particles. In addition, various hypothetical mechanisms may contribute to the creation of different molecular chiralities.
Jeffrey Badda, professor emeritus at the University of California, San Diego and the Scripps Institution of Oceanography, is skeptical of the concept. He questioned the rationality of RNA as the initial self-replicating molecule under early conditions. Bada highlighted that in the prebiotic environment, there is a lack of evidence for successful RNA creation due to the many stability issues surrounding the molecule. However, Sutherland's team is still working to demonstrate the formation of two other nucleotides in the RNA precursor molecule. Sutherland said his team could make the opposite view, as he has been holding on to that view for 22 years.
Whether the CISS effect is part of the solution, or not at all, a clear future phase is needed to further examine it. Asavel highlights the favorable aspects of this hypothesis: its creativity, feasibility, and testability, making it an interesting hypothesis to explore. He believes that the next most high-profile step will be to present geological evidence that the process may have taken place outside of the laboratory environment.
Oztec showed off a flat black rock he had collected during his trip to Australia at the Speed** conference. Australia is a region rich in magnetic ferruline rocks, and his goal is to reproduce his experiments there. He plans to intensify future experiments by incorporating more dynamic elements. He envisioned experiments in ancient lakes where early molecules appeared, characterized by streams and material flows that flowed through them, and a natural cycle of wetness and dryness, driven by rainfall and high temperatures, which could promote the formation and dissolution of crystals, a cyclical process.
The mystery surrounding same-sex remains, but Ozturk's work in explaining the CISS effect is enthusiastically supported by mentors. Messerson is a renowned geneticist and molecular biologist known for experimentally confirming DNA replication. Subsequently, the 93-year-old geneticist told Ozturk that he was happy to be alive to see the issue unfold.
If you are interested in the article, please follow me or leave me a message