The building blocks of life may have reached Earth by meteorites

For the first time, scientists have discovered all the major building blocks of DNA that mysterious previous discoveries have failed to detect in meteorites. . This suggests that cosmic collisions may have helped bring these essential nutrients to life on ancient Earth. They are called adenine (A), thymine (T), cytosine (C) and guanine (G). The other sister molecule, RNA, also uses A, C, and G, but thymine has been replaced by uracil (U).

• There are two types of nucleobases, called "purines" and "pyrimidine". (Pyramidines) are known. The nucleobases previously seen in meteorites are both purines, each made of a hexagonal molecule combined with a pentagonal molecule. Those not yet discovered in space rocks are pyrimidines that have smaller structures, each composed of only one hexagonal molecule.

  Why only purines and not pyrimidines are found in meteorites has long been a mystery. Was. Previous laboratory studies simulating outer space conditions have shown that both purines and pyrimidines can be formed during light-induced chemical reactions in interstellar molecular clouds, and then these compounds can be formed during the formation of the solar system and asteroids. . Such chemical reactions may also have occurred directly in space rocks.

  Now, however, scientists have finally identified all the pyrimidines and purines in DNA and RNA in meteorites that have reached Earth. "The presence of five major nucleobases in meteorites may predate genetic function," said Yasuhiro Oba (pyrimidines) astronomer at Hokkaido University in Japan and lead author of a study published in the April 26 issue of the journal Nature. The beginning of life plays a role in the early earth. "

  

  Credit: NASA/Goddard Space Flight Center

  To identify these nucleotide bases, researchers used advanced analytical methods that were initially used in genetic research. And a drug was designed to detect very small amounts of organic bases with an accuracy of a fraction of a trillion. According to Obama, this is at least 10 to 100 times more sensitive than previous methods used to detect pyrimidines in meteorites.

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  In this research, scientists found examples of three carbon-rich meteorites or carbon meteorites, the Murchison, Murray, and Lake Tagish meteorites. Tagish), which according to previous research could host a variety of chemical reactions to form the bases of nucleotide bases.

  Thus, they were able to identify T, C, and U at levels up to a fraction of a billion in meteorites. Interestingly, these compounds were present in concentrations similar to those predicted by previous experiments that mimicked the conditions before the formation of the solar system. In addition to the important compounds T, C, and U, pyrimidine scientists Others found that they are not used in DNA or RNA, thus confirming the ability of meteorites to carry more of these compounds. "Based on our findings, we can say that the nucleotide bases in carbon meteorites are also of a wide variety," Obama said. According to Obama, one clue could be that purines have a pentagonal ring known as imidazole, whereas pyramidines do not. Imidazole and similar molecules. These meteorites are much more abundant than pyrimidines, which suggests that they may be easier to combine for the natural occurrence of chemical reactions. In addition, imidazole can act as a primary catalyst and initiate chemical reactions such as the formation of purines instead of pyramidines.

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  Cover Photo: Graphic design of the arrival of the elements Creating life on Earth by meteors
  Credit: NASA Goddard/CI Lab/Dan Gallaghe

source: Space