New discoveries about natural Peptide formation an important step RNA/DNA formation. The simplicity of the solution is amazing.
Scientists Made a Breakthrough on Life’s Origin and It Could Change Everything
A new study shows that ingredients for life can form from non-living chemicals on any given beach, and it could help develop new drugs and search for alien life.
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Becky Ferreira
October 3, 2022, 3:39pm
Scientists have achieved a major breakthrough toward unraveling the mystery of how life first arose on Earth and whether it might exist elsewhere in the universe, reports a new study.
A longstanding mystery—perhaps
the mystery, existentially speaking—is how life originated from non-living, or abiotic, chemicals. For the first time ever, researchers at Purdue University have shown that peptides, which are strings of amino acids that are crucial building blocks of life, can spontaneously form in droplets of water during rapid reactions that occur when water meets the atmosphere—for example, when a wave hits a rock and throws up a misty spray. This could occur in conditions similar to those that existed on Earth some 4 billion years ago, when life first took hold on our planet.
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The discovery provides “a plausible route for the formation of the first biopolymers,” which are complex structures produced by living organisms, according to
a study published Monday in
Proceedings of the National Academy of Sciences. The team says the discovery could even speed up the development of novel drugs and medical treatments by providing a new medium for fostering rapid chemical reactions.
“There are a very large number of studies showing peptide formation, but they all use catalysts or modified amino acids to make species unlikely to exist naturally,” said R. Graham Cooks, who serves as the Henry B. Hass Distinguished Professor of Analytical Chemistry at Purdue and senior author of the study, in an email.
Cooks and his colleagues have now shown that peptides readily form in the kinds of chemical systems that existed on ancient Earth, such as sea spray from our planet’s primordial oceans or freshwater dribbling down slopes.
“The most interesting implication is that similar chemistry explains other essential biological polymers, not just peptides,” he noted, adding that his team plans to publish more on this topic soon.
In other words, the new study has opened a rare window into the murky early years on our planet when nonliving compounds somehow assembled themselves into living organisms, a still-unexplained transformation known as abiogenesis. The formation of peptides is an important step in abiogenesis because these structures form the basis of biomolecules such as proteins, which can perform the self-replicating mechanisms that are necessary for life.
The team was able to reconstruct the possible formation of these peptides by running “droplet fusion” experiments that simulate how water droplets collide in the air, which Cooks described as “like two kids with garden hoses spraying each other.”
These experiments show that the surface of the droplets, where water meets air, is a region that can be exceptionally productive at spinning peptides out of the types of amino acids that have been delivered to Earth by meteorites for billions of years. As a result, the experiments offer a possible solution to what’s known as the “water paradox,” a problem that has puzzled scientists in the abiogenesis field for years.
“The water paradox is the contradiction between (i) the very considerable evidence that the chemical reactions leading to life occurred in the prebiotic ocean and (ii) the thermodynamic constraint against exactly these (water loss) reactions occurring in water,” Cooks explained. “Proteins are formed from amino acids by loss of water” and “loss of water in water will not occur because the process will be reversed by the water (thermodynamically forbidden).”
Put another way, peptides need some level of dehydration to form, but that is very hard to accomplish in a hydrated environment like a water droplet. For more than a decade, Cooks and his colleagues have shown that microdroplets have many unique characteristics, including an accelerated reactivity at their surfaces. These air-water interfaces are like a reverse oasis—that is, a dry refuge in the watery world of a droplet—that enables the loss-of-water reactions needed to build peptides out of amino acids.
Getting back into the proper spirit of this thread:
How did life begin? How did chemical reactions on the early Earth create complex, self-replicating structures that developed into living things as we know them? According to one school of thought, before the current era of DNA-based life, there was a kind of molecule called RNA (or ribonucleic...
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How did life begin? How did chemical reactions on the early Earth create complex, self-replicating structures that developed into living things as we know them?
According to one school of thought, before the current era of DNA-based life, there was a kind of molecule called RNA (or ribonucleic acid). RNA – which is still a crucial component of life today – can replicate itself and catalyse other chemical reactions.
But RNA molecules themselves are made from smaller components called ribonucleotides. How would these building blocks have formed on the early Earth, and then combined into RNA?
Chemists like me are trying to recreate the chain of reactions required to form RNA at the dawn of life, but it's a challenging task. We know whatever chemical reaction created ribonucleotides must have been able to happen in the messy, complicated environment found on our planet billions of years ago.
I have been studying whether "autocatalytic" reactions may have played a part. These are reactions that produce chemicals that encourage the same reaction to happen again, which means they can sustain themselves in a wide range of circumstances.
In
our latest work, my colleagues and I have integrated autocatalysis into a well-known chemical pathway for producing the ribonucleotide building blocks, which could have plausibly happened with the simple molecules and complex conditions found on the early Earth.
The formose reaction
Autocatalytic reactions play crucial roles in biology, from regulating our heartbeats to forming patterns on seashells. In fact, the replication of life itself, where one cell takes in nutrients and energy from the environment to produce two cells, is a particularly complicated example of autocatalysis.
A chemical reaction called the formose reaction, first discovered in 1861, is one of the best examples of an autocatalytic reaction that could have happened on the early Earth.
In essence, the formose reaction starts with one molecule of a simple compound called glycolaldehyde (made of hydrogen, carbon and oxygen) and ends with two. The mechanism relies on a constant supply of another simple compound called formaldehyde.
A reaction between glycolaldehyde and formaldehyde makes a bigger molecule, splitting off fragments that feed back into the reaction and keep it going. However, once the formaldehyde runs out, the reaction stops, and the products start to degrade from complex sugar molecules into tar.
The formose reaction shares some common ingredients with a well-known chemical pathway to make ribonucleotides, known as the Powner–Sutherland pathway. However, until now no one has tried to connect the two – with good reason.
The formose reaction is notorious for being "unselective". This means it produces a lot of useless molecules alongside the actual products you want.
An autocatalytic twist in the pathway to ribonucleotides
In our study, we tried adding another simple molecule called cyanamide to the formose reaction. This makes it possible for some of the molecules made during the reaction to be "siphoned off" to produce ribonucleotides.
The reaction still does not produce a large quantity of ribonucleotide building blocks. However, the ones it does produce are more stable and less likely to degrade.
What's interesting about our study is the integration of the formose reaction and ribonucleotide production. Previous investigations have studied each separately, which reflects how chemists usually think about making molecules.
Generally speaking, chemists tend to avoid complexity so as to maximise the quantity and purity of a product. However, this reductionist approach can prevent us from investigating dynamic interactions between different chemical pathways.
These interactions, which happen everywhere in the real world outside the lab, are arguably the bridge between chemistry and biology.
Industrial applications
Autocatalysis also has industrial applications. When you add cyanamide to the formose reaction, another of the products is a compound called 2-aminooxazole, which is used in chemistry research and the production of many pharmaceuticals.
Conventional 2-aminooxazole production often uses cyanamide and glycolaldehyde, the latter of which is expensive. If it can be made using the formose reaction, only a small amount of glycolaldehyde will be needed to kickstart the reaction, cutting costs.
Our lab is currently optimising this procedure in the hope we can manipulate the autocatalytic reaction to make common chemical reactions cheaper and more efficient, and their pharmaceutical products more accessible. Maybe it won't be as big a deal as the creation of life itself, but we think it could still be worthwhile.
Quoc Phuong Tran, PhD Candidate in Prebiotic Chemistry, UNSW Sydney
This article is republished from The Conversation under a Creative Commons license. Read the original article.
