Making the Stuff of Life in One Batch

Common origins of RNA, protein and lipid precursors in a cyanosulfidic protometabolism : Nature Chemistry : Nature Publishing Group.

Life is built on chemistry, but the chemistry required to jump from the basic amino acids and small organic molecules expected on the Early Earth to the components of Life-As-We-Know-It – lipids, proteins and nucleic acids – has been obscure, until now. The scenario outlined in Nature Chemistry [doi:10.1038/nchem.2202] also explains why the various chemical components of our kind of life are so very similar. Even though they perform quite different roles, the building blocks are similar, produced originally by very similar chemical processes.

Original caption: The degree to which the syntheses of ribonucleotides, amino acids and lipid precursors are interconnected is apparent in this ‘big picture’. The network does not produce a plethora of other compounds, however, which suggests that biology did not select all of its building blocks, but was simply presented with a specific set as a consequence of the (photo)chemistry of **hydrogen cyanide** (11) and **hydrogen sulfide** (12), and that set turned out to work. To facilitate the description of the chemistry in the text, the picture is divided into four parts:

(a) Reductive homologation of *hydrogen cyanide* (11) (bold green arrows) provides the C2 and C3 sugars — **glycolaldehyde** (1) and **glyceraldehyde** (4)—needed for subsequent ribonucleotide assembly (bold blue arrows), but also leads to precursors of *Glycine*, *Alanine*, *Serine* and *Threonine*.

(b) Reduction of **dihydroxyacetone** (17) (the more stable isomer of *glyceraldehyde* (4)) gives two major products, **acetone** (18) and **glycerol** (19). Reductive homologation of acetone (18) leads to precursors of *Valine* and *Leucine*, whereas phosphorylation of *glycerol* (19) leads to the lipid precursor **glycerol-1-phosphate** (21).

(c) Copper(I)-catalysed cross-coupling of *hydrogen cyanide* (11) and **acetylene** (32) gives **acrylonitrile** (33), reductive homologation of which gives precursors of *Proline* and *Arginine*.

(d) Copper(II)-driven oxidative cross-coupling of hydrogen cyanide (11) and acetylene (32) gives **cyanoacetylene** (6), which serves as a precursor to *Asparagine*, *Aspartic acid*, *Glutamine* and *Glutamic acid*. Pi, inorganic phosphate.

The key-point is the relatedness and the step-by-step creation of one component or another, by short chemical processes, from the basic materials. To have produced such serial chemistry would have required means of isolating the raw materials and products, then mixing them. The next image from the paper provides a hint of what would’ve been required, on some sun-drenched landscape, swept by occasional rains, in an atmosphere of (probably) H2, N2, CO2 and H2O…