Modern physics can explain everything, from the spin of the smallest particle to the behavior of entire clusters of galaxies. But it cannot explain life. There is no formula that determines the difference between a piece of living matter and a piece of dead matter. Life seems to mysteriously “emerge” from non-living components such as elementary particles. Assembly theory, the outline of which was recently published in Nature, is a bold approach to explaining life at the most fundamental scale. It is based on two key concepts: complexity and information (such as that contained in DNA). The new theory allows us to understand how both arise in chemical systems.
“Emergency” is a word physicists use to explain something that is greater than the sum of its parts. For example, how water can be perceived as wet while the individual water molecules are not. Humidity is therefore an emergent property. Although it is a mathematically elegant theory, it can only be reliable if tested in the laboratory. In order for the abstractions of the assembly hypothesis to be anchored in chemical reality, it is important to conduct carefully planned experiments like the one my colleagues and I are conducting.
The core of assemblage theory is the idea that objects can be defined not as immutable entities but by the history of their creation. This brings us to the processes by which complex configurations are built from simpler building blocks. The theory proposes an “assembly index” that quantifies the minimum steps or shortest path required to assemble an object. This measure measures the degree of “selection” required to produce a set of objects in relation to memory – such as: B. DNA – which is required for the creation of living things.
After all, living things do not arise spontaneously, like helium in stars. You need DNA as a template to create new versions.
Fifteen steps to creating a life molecule
But how could these theoretical constructions be verified experimentally? A central aspect of the new theory has already been tested in our laboratory. This involves determining the assembly index using mass spectrometry, an analytical instrument that can be used to measure the relationship between mass and charge of molecules.
By fragmenting molecules and analyzing their mass spectra, we can estimate their rate of assembly. This means we can literally see how many steps it takes for different fragments to combine into a particular molecule. This index can also be measured using other techniques such as infrared spectroscopy and nuclear magnetic resonance spectroscopy.
As part of our research, we were able to determine the assembly rate for a number of molecules in the laboratory and through computer simulations. Our work shows that molecules associated with life, such as hormones and metabolites (products of metabolic reactions), are actually more complex and require more information to assemble than molecules not exclusively associated with life, such as carbon dioxide. Carbon.
In fact, we have shown that an assembly rate of more than 15 steps is only found in molecules related to living things, as theory suggests.
The assembly hypothesis also offers ideas about the origin of life that can be tested. As he posits, there is a point at which molecules become so complex that they begin to use information to make copies of themselves – they suddenly need memory and information – a kind of threshold at which life emerges from non-life.
Ultimately, non-biological systems may acquire selective capacity and minimal memory (just as the Sun formed the planets by accumulating large amounts of mass). But the existence of living organisms or the technology they create, from Lego to space science, is not possible without high levels of memory and choice.
chemical soup
We plan to further study this origin of life by creating a type of chemical soup in our laboratory. In such a soup, entirely new molecules could emerge over time, either by adding different reagents or by chance, as we control their rate of assembly and the growth of the system. By adjusting the reaction rates and conditions, we could study this fascinating transition point from non-life to life and find out whether it follows the predictions of assemblage theory.
We also develop “chemical soup generators” that mix simple chemicals into complex ones. These generators can help us better understand how complexity can be built with assembly theory and how selection can be initiated outside of biology.
This could give us a clue to how life originally evolved, starting with minimal choice and progressing to more and more demands. Are objects constructed in a predictable manner under identical conditions? Or does chance come into play at some point? This would help us understand whether the origin of life is deterministic and predictable or, on the contrary, rather chaotic.
Assembly theory could be applied beyond molecules and stimulate studies of other systems that rely on combinations, such as material aggregates, polymers, or artificial chemistry. This could lead to new scientific knowledge or technological innovations. It could reveal subtle patterns by which molecules possess certain properties disproportionately above a minimum assembly rate.
It would also be possible to use the theory to study evolution itself. Researchers could study the role of cell fragments in the formation of a whole cell, which in turn are formed from smaller molecules that combine to form amino acids and nucleotides. Tracking the emergence of metabolic and genetic networks in this way could provide clues to transitions in evolutionary history.
Tracking how objects are assembled requires precise experimental monitoring, but it can be worthwhile. Assemblage theory promises a radical new understanding of matter, with the possibility of discovering universal principles of hierarchical construction that go beyond biology.
Complex configurations of matter may not be immutable objects, but rather reference points in an open construction process that propagates over time. The universe may obey certain physical laws, but ultimately it is creative.
Lee Cronin He is a researcher at the University of Glasgow
This article was originally published in The conversation.
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