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RNA world easier to make : Nature News

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John Sutherland and his colleagues from the University of Manchester, UK

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ribonucleotide

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building block of RNA

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'RNA world' hypothesis, which suggests that life began when RNA, a polymer related to DNA that can duplicate itself and catalyse reactions

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strong evidence for the RNA world

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Donna Blackmond, a chemist at Imperial College London.

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RNA polymer is a string of ribonucleotides

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three distinct parts: a ribose sugar, a phosphate group and a base

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chemists had thought the subunits would probably assemble themselves first, then join to form a ribonucleotide

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efforts to connect ribose and base together have met with frustrating failure

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researchers have now managed to synthesise

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ribonucleotides

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remedy is to avoid producing separate ribose-sugar and base subunits

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makes a molecule whose scaffolding contains a bond that will

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be the key ribose-base connection

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atoms are then added around this skeleton

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final connection is to add a phosphate group

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influences the entire synthesis

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acting as a catalyst, it guides small organic molecules into making the right connections

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What we have ended up with is molecular choreography

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objectors to the RNA-world theory say the RNA molecule as a whole is too complex to be created using early-Earth geochemistry

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flaw is in the logic — that this experimental control by researchers in a modern laboratory could have been available on the early Earth

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Robert Shapiro, a chemist at New York University

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early-Earth scenarios

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heating molecules in water, evaporating them and irradiating them with ultraviolet light

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results showing that they can string nucleotides together

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ultimate goal is to get a living system (RNA) emerging from a one-pot experiment

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need to know what the constraints on the conditions are first

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another theory of life's origins

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Shapiro sides with

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because RNA is too complex to emerge from small molecules, simpler metabolic processes

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eventually catalysed the formation of RNA and DNA

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