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takyon writes:

Amyloids may have been the "precursors of life" rather than RNA molecules:

The story starts at least four billion years ago, when there was no living matter on the planet. Sometime around then, smaller chemical compounds formed into larger organised structures capable of self-reproduction. And so the early precursors of life were born. Exactly which molecules were involved, and what they were made of, is the biggest puzzle in evolutionary history. However, ETH Professor Roland Riek and his senior scientist Jason Greenwald have a compelling idea: these primordial lifelike structures could well have been proteinaceous aggregates, or amyloids. The latest results of their laboratory research now lend weight to their hypothesis.

The scientists performed an experiment to demonstrate that it is remarkably easy for such amyloid structures to assemble spontaneously from building blocks that existed on the prebiotic Earth, and under reaction conditions that also seem plausible for the primeval era. The scientists used four simple amino acids as starting materials: glycine, alanine, aspartate and valine. In addition, they used carbonyl sulphide as a catalyst for the reaction. This volcanic gas is also likely to have existed in the atmosphere billions of years ago. In the laboratory experiment, the amino acid molecules spontaneously assembled, with the help the carbonyl sulphide, into short chains (peptides) comprising between 5 and 14 building blocks. These chains in turn arranged themselves in parallel into amyloid structures known as beta sheets. In the experiment, these sheet structures took the form of fibres and typically comprised thousands of adjoining peptide chains which the scientists were able to identify using an electron microscope.

Amyloid Aggregates Arise from Amino Acid Condensations under Prebiotic Conditions (DOI: 10.1002/anie.201605321) (DX)

Towards Prebiotic Catalytic Amyloids Using High Throughput Screening (open, DOI: 10.1371/journal.pone.0143948) (DX)

Original Submission