Meteorite-common Amino Acid Induces Formation Of Nanocavities In Clay Mineral
Researchers at the universities of Amsterdam and Utrecht have observed the formation of nanocavities in montmorillonite clay under exposure to gamma-aminobutyric acid, a molecule commonly found on meteorites.
This hitherto unrecognised phenomenon could be relevant to the origin of life on Earth, by introducing 3D confined nano-environments in clay that might have facilitated life’s first chemistry. The findings have been reported in a paper in Communications Earth & Environment, a journal from the Nature family.
The research, carried out as a part of the Planetary and ExoPlanetary Science Programme (PEPSci) of the Dutch Research Council NWO, adds a novel dimension to the concept of the ‘warm little pond’. This primordial pond would have enabled the interaction of organics and minerals in a shallow water environment.
The catalytic action of the minerals could thereby have led to the creation of the first molecules of life from simpler organic building blocks. Much research has been carried out into the interaction of clay minerals with organic molecules, especially those that could lead to the formation of Earth-like bio-polymers such as proteins and RNA.
The prebiotic molecular inventory, however, is expected to be diverse, also including molecules that were introduced to the Earth’s atmosphere through meteorites. In a novel approach, PhD candidate Orr Rose Bezaly and her supervisors Helen King (Utrecht University) and Annemieke Petrignani (University of Amsterdam) have now focused on the role of gamma-aminobutyric acid (GABA), a small molecule commonly found on meteorites. It has no known role in protein synthesis and has only a weak interaction with clays.
According to Petrignani it thus is a rather ‘unusual suspect’ regarding the origin of life. “However, because of its widespread occurrence on meteorites, we thought it would be interesting to investigate its potential role. The results really surprised us!”
a, b Control sample showing typical layering (white arrows) and its natural variability without GABA exposure. c–f Sample exposed to 2 M GABA, illustrating widespread disruptions that enhance variability and the manifestation of nanocavities (black arrows). Both samples had 18% water weight gain. Communications Earth & Environment
Partial exfoliation leading to nanocavities
In laboratory experiments, the researchers exposed the common clay montmorillonite (a layered aluminosilicate mineral) to a range of GABA concentrations. Using infrared spectroscopy, X-ray crystallography and transmission electron microscopy, they were able to reveal that the weak interaction of GABA with the clay induce a process of partial exfoliation, where clay layers are ‘peeled away’. The process, that initiates in the mid-layers of the clay, is also correlated with the formation of nanoscale cavities in between clay layers.
According to Petrignani, exfoliation is widely investigated, especially in material sciences, but this atypical partial exfoliation has not been addressed and is also new in the field of origin of life. “We are the first to report on this, and we think it can be quite relevant. The nanoscale cavities we observe could facilitate the compartmentalisation that is a fundamental requirement of a prebiotic system.”
Orr Rose Bezaly explains that such nanocompartments can foster a local disequilibrium within the larger scale prebiotic chemical environment, driving the synthesis of crucial molecules. “In the prebiotic context this is most relevant to chemistry that requires low water activity, such as polymerisation.
This should somehow be coupled with compartmentalisation – another critical function of life. Our discovery thus points us towards a feasible research route aimed at understanding nanoscale processes leading to the emergence of life. Beyond this field, the exfoliation method described in our work may be used as a sustainable technique for clay treatment for manipulation and synthesis of new materials”.
An exciting lead for new research
Petrignani is excited but emphasizes that it is too early to make any claims. “We need more research to obtain deeper insights, for instance into the chemical dynamics in the nanocavities, what formation pathway could be induced, and also if novel, larger molecules are formed, how these could then leave the cavities. So we do see compartments emerging and we think these could play a role in the emergence of life. But we are far from being able to say that with certainty.”
Meteorite-common amino acid induces clay exfoliation and abiotic compartment formation, Communications Earth & Environment (open access)
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