Scientists think they've found primordial goop whence life first sprang

A speculative new study suggests that nucleic acids, proteins and cell membranes – precursors to life Earth – first grew from a single kickstarting molecule named diamidophosphate.

Its previous claim to fame was a 2008 barley fertilisation experiment, published in Biologia Plantarum, which found ammonium diamidophosphate compounds had "nutritive value for plants".

Ramanarayanan Krishnamurthy, an origins-of-life scientist at the Scripps Research Institute in La Jolla, California, told The Register: "On a philosophical level, if we understand how we became, and where we came from, it may provide solutions to how we should move forward and where we can go."

Scientists say there's no way to really find out the precise chemistry of day zero, but they've been testing ideas in the lab all the same. The new study, appearing this week in Nature Chemistry, found that diamidophosphate in aqueous solution soups could simultaneously catalyse the growth of important biological building blocks called purine-nucleotides, phospholipids and oligopeptides.

Purine-nucleotides are found in DNA and RNA, phospholipids in cell membranes and oligopeptides are made of amino acids.

Researchers have brewed old-school nucleotides in desert-like conditions using a cocktail of phosphate (without carbon) and four other molecules. They've also created oligopeptides via dehydration in chemical reactions or phospholipids via acids and alcohols.

Krishnamurthy, who was senior author on the work led by Clémentine Gibard, said his group showed you could "do it all in the same locale (like what you find within a cell)" while "using the same type of chemistry".

He said this would let different classes of molecule exist at the same time and hence evolve together.

However, the wider scientific community isn't one to accept such studies as read.

"The 'simplest' ideas are typically the most desirably as they suggest pathways to life that are more plausible," said Brian Cafferty, a postdoctoral researcher at Harvard University in Cambridge, Massachusetts.

He described the study as "highly appealing" although wanted to know how the reactions fared in complex mixtures of amino acids, nucleosides and fatty acids.

Henderson Cleaves, a researcher at Tokyo Institute of Technology in Japan, said it is "hard to say how stable" the molecule is.

Takeshi Kakegawa, of Tokohu University in Sendai City, Japan, said diamidophosphate "is not perfect for origin of life" because it can't make "structured" and "functioned" molecules such as double-helix RNA.

"Their experimental products are still far from life except cell-like structures," he added.

"The biggest question is how to prepare [diamidophosphate] on the early Earth with enough quantity." He doubts that meteoritic minerals, as the authors suggest as a possibility, could have done so.

Matthew Pasek, a researcher at University of South Florida in Tampa, said the diamidophosphate theory "is a good answer" to the grand origin question. Even if there might not be a way to prove it, some ideas "might end up to be more likely than others".

"I think there's a good route to making this out there, and that it will be shown that this compound can be made on the early Earth, but it hasn't been shown yet."

Krishnamurthy said the lab is hunting for the sources of diamidophosphate and similar molecules on early Earth, examining "the scope" of this chemistry and whether it will all work in a primitive cell-like structure. ®

Bootnote

The paper authors used the same acronym for diamidophosphate (N₂H₄PO₂H) – DAP – as the common fertiliser, diammonium phosphate ((NH₄)₂HPO₄). However, although diamidophosphate contains nitrogen atoms chemically bonded to phosphorous, the common fertiliser does not. So even though diamidophosphate has been investigated previously as a possible fertiliser, to avoid confusion we did not use the acronym.