UV radiation in space-like conditions can produce uracil, possibly source of primitive life RNA

[steven johnson]

Molecules of pyrimidine, polycyclic aromatic hydrocarbons, have been identified in meteorites and could have survived long enough to migrate into interstellar dust clouds where they froze onto dust grains.

Scientists created a simulated environment where uracil was synthesized from pyrimidine under ultraviolet radiation. This could have been a missing link in the creation of the conditions on primitive earth for life to have formed.

ScienceDaily (Nov. 11, 2009) — NASA scientists studying the origin of life have reproduced uracil, a key component of our hereditary material, in the laboratory. They discovered that an ice sample containing pyrimidine exposed to ultraviolet radiation under space-like conditions produces this essential ingredient of life.

Pyrimidine is a ring-shaped molecule made up of carbon and nitrogen and is the basic structure for uracil, part of a genetic code found in ribonucleic acid (RNA). RNA is central to protein synthesis, but has many other roles.

"We have demonstrated for the first time that we can make uracil, a component of RNA, non-biologically in a laboratory under conditions found in space," said Michel Nuevo, research scientist at NASA's Ames Research Center, Moffett Field, Calif. "We are showing that these laboratory processes, which simulate occurrences in outer space, can make a fundamental building block used by living organisms on Earth."

They found that when pyrimidine is frozen in water ice, it is much less vulnerable to destruction by radiation. Instead of being destroyed, many of the molecules took on new forms, such as the RNA component uracil, which is found in the genetic make-up of all living organisms on Earth.


NASA Reproduces A Building Block Of Life In Laboratory

[nadinbrzezinski]

1. This is one more step for Panspermia

GOOL

This is also more evidence that life will exist AWAY from EARTH.

[eppur_se_muova]

2. Meh. Minor (if not trivial) discovery, vigorous PR.

Lots better ways to make uracil. Retrosynthesis suggests one acetaldehyde, two ammonia, and two CO2 molecules, or (more likely) their synthetic equivalents.

In contrast to the purines, the routes that have been proposed for the prebiotic synthesis of pyrimidines from simple precursors give only low yields. Cytosine can be synthesized from cyanoacetylene and cyanate; the former precursor is produced from a spark discharge in a CH4/N2 mixture and is an abundant interstellar molecule. But this reaction requires relatively high concentrations of cyanate (> 0.1 M), which are unlikely to occur in aqueous media as cyanate is hydrolysed rapidly to CO2 and NH3. An alternative route that has been explored is the reaction of cyanoacetaldehyde (formed by hydrolysis of cyanoacetylene) with urea. But at low concentrations of urea, this reaction produces no detectable quantities of cytosine. Here we show that in concentrated urea solution--such as might have been found in an evaporating lagoon or in pools on drying beaches on the early Earth--cyanoacetaldehyde reacts to form cytosine in yields of 30-50%, from which uracil can be formed by hydrolysis. These reactions provide a plausible route to the pyrimidine bases required in the RNA world.


http://www.epidna.com/showabstract.php?pmid=7596408&redirect=yes&terms=acetaldehyde+makes+uracil

First law of photosynthetic chemistry: never make anything by a photosynthetic reaction if there is an alternative. The reaction described in the OP might account for a tiny percantage of all the uracil in the universe. Any uracil found on planetary surfaces is probably formed by good old condensation chemistry.