Chemists claim to have solved riddle of howlife began on Earth18 March 2015, by Bob Yirka

Chemistry in a post-meteoritic-impact scenario. A seriesof post-impact environmental events are shown alongwith the chemistry (boxed) proposed to occur as aconsequence of these events. a, Dissolution ofatmospherically produced hydrogen cyanide results inthe conversion of vivianite (the anoxic corrosion productof the meteoritic inclusion schreibersite) into mixedferrocyanide salts and phosphate salts, with countercations being provided through neutralization and ion-exchange reactions with bedrock and other meteoriticoxides and salts. b, Partial evaporation results in thedeposition of the least-soluble salts over a wide area,and further evaporation deposits the most-soluble saltsin smaller, lower-lying areas. c, After completeevaporation, impact or geothermal heating results inthermal metamorphosis of the evaporite layer, and thegeneration of feedstock precursor salts (in bold). d,Rainfall on higher ground (left) leads to rivulets orstreams that flow downhill, sequentially leachingfeedstocks from the thermally metamorphosed evaporitelayer. Solar irradiation drives photoredox chemistry inthe streams. Convergent synthesis can result whenstreams with different reaction histories merge (right), asillustrated here for the potential synthesis of arabinoseaminooxazoline at the confluence of two streams thatcontained glycolaldehyde, and leached differentfeedstocks before merging. Credit: (c) Nature Chemistry

(2015) doi:10.1038/nchem.2202

(Phys.org)A team of chemists working at the MRCLaboratory of Molecular Biology, at Cambridge inthe UK believes they have solved the mystery ofhow it was possible for life to begin on Earth overfour billion years ago. In their paper published inthe journal Nature Chemistry, the team describeshow they were able to map reactions that producedtwo and three-carbon sugars, amino acids,ribonucleotides and glycerolthe materialnecessary for metabolism and for creating thebuilding blocks of proteins and ribonucleic acidmolecules and also for allowing for the creation oflipids that form cell membranes.

Scientists have debated for years the variouspossibilities that could have led to life evolving onEarth, and the arguments have only grown moreheated in recent years as many have suggestedthat it did not happen here it all, instead, it wasbrought to us from comets or some other celestialbody. Most of the recent debate has foundscientists in one of three chicken-or-the-egg firstcamps: RNA world advocates, metabolism-firstsupporters and those who believe that cellmembranes must have developed first.

The chemists with this new effort believe they havefound a way to show that all three arguments areboth right and wrongthey believe they have founda way to show that everything necessary for life toevolve could have done so from just hydrogensulfide, hydrogen cyanide and ultraviolet light andthat those building blocks could have all existed atthe same timein their paper, they report that usingjust those three basic ingredients they were able toproduce more than 50 nucleic acidsprecursors toDNA and RNA molecules. They note that earlymeteorites carried with them ingredients that wouldreact with nitrogen already in the atmosphere,producing a lot of hydrogen cyanide. By dissolving

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in water, it could have very easily come into contactwith hydrogen sulfide, while being exposed toultraviolet light from the sun. And that, they claim,would have been all that was needed to get thingsgoing.

The findings by the team are sure to garner a greatdeal of interest in the scientific community andothers will no doubt be testing and commenting ontheir findings. If what they claim passes muster,their work will likely be remembered as one of thegreat achievements of our time.

More information: Common origins of RNA,protein and lipid precursors in a cyanosulfidicprotometabolism, Nature Chemistry (2015) DOI:10.1038/nchem.2202

AbstractA minimal cell can be thought of as comprisinginformational, compartment-forming and metabolicsubsystems. To imagine the abiotic assembly ofsuch an overall system, however, places greatdemands on hypothetical prebiotic chemistry. Theperceived differences and incompatibilities betweenthese subsystems have led to the widely heldassumption that one or other subsystem must havepreceded the others. Here we experimentallyinvestigate the validity of this assumption byexamining the assembly of various biomolecularbuilding blocks from prebiotically plausibleintermediates and one-carbon feedstock molecules.We show that precursors of ribonucleotides, aminoacids and lipids can all be derived by the reductivehomologation of ?hydrogen cyanide and some of itsderivatives, and thus that all the cellularsubsystems could have arisen simultaneouslythrough common chemistry. The key reaction stepsare driven by ultraviolet light, use ?hydrogen sulfideas the reductant and can be accelerated byCu(I)Cu(II) photoredox cycling.

2015 Phys.org

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APA citation: Chemists claim to have solved riddle of how life began on Earth (2015, March 18) retrieved 19March 2015 from http://phys.org/news/2015-03-chemists-riddle-life-began-earth.html

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