Astrobiologists, supported by NASA, have announced a major
advance in understanding how life may have originated on Earth
billions of years ago.
A team of scientists report in the January 9 issue of Science
that ribose and other simple sugars that are among life’s
building blocks could have accumulated in the early earth’s
oceans if simple minerals, such as borax, were present.
Ribose is a key component of ribonucleic acid (RNA). It is also
a precursor for deoxyribonucleic acid (DNA). RNA and DNA,
together called”nucleic acids”, are required for all known
life, where they enable inheritance, genetics, and evolution.
“Many building blocks in biology can be formed without life”,
said Steven Benner, Distinguished Professor in the Departments
of Chemistry and Anatomy and Cell Biology at the University of
Florida, Gainesville, and the leader of the team. “Fifty years
ago, Stanley Miller did a famous experiment that generated
amino acids by passing electrical sparks through a primitive
atmosphere. This was a key step to understanding how proteins
might have originated. But without nucleic acids, proteins
appeared to be useless, unable to have children,” he said.
For those interested in the origin of life, making RNA and DNA
has been the key unsolved problem. This is in large part
because ribose, needed to form RNA and DNA, is unstable and
easily forms brown tars unless kept cold. “Ribose and
electrical sparks are simply not compatible,” Benner said. “We
knew that ribose and other sugars decompose easily. This
happens in your kitchen when you bake a cake for too long. It
turns brown as the sugars decompose to give other things.
Eventually, the cake becomes asphalt,” added Benner.
Recognizing ribose had a particular chemical structure that
allowed it to bind to borate, Benner added the mineral
colemanite. “Colemanite is a mineral containing borate found in
Death Valley. Without it, ribose turns into a brown tar. With
it, ribose and other sugars emerge as clean products,” Benner
said. He then showed that other borate minerals did the same
trick, including ulexite and kernite. The latter is more
commonly known as borax. Borax is mined from Death Valley,
Calif. and is used in certain detergents to wash clothing.
“This is only one of several steps that must be taken to
convert simple organic molecules found in the cosmos to life,”
Benner cautioned. “Much work remains to be done. We are just
surprised that such a simple idea has gone unexploited for so
long,” he added.
“Steve Benner’s clever work has taken us closer to revealing
the origin of life on Earth and furthered NASA’s understanding
of the potential for life elsewhere in the universe,” said
Michael Meyer, Senior Scientist for Astrobiology at NASA
Headquarters, Washington.
The NASA Astrobiology Institute supports nodes at universities
and non-profit organizations around the United States. Its goal
is to understand the origin, evolution, distribution and fate
of life in the universe. The Benner group has been a member of
the NASA Astrobiology Institute for five years. “Without
ongoing, stable support from NASA, this work would not have
been possible,” Benner said.
Also contributing to the research were Alison Olcott, an
assistant at the Wrigley Institute on Catalina Island, Calif;
Alonso Ricardo, a graduate student at the University of
Florida; and Dr. Matthew Carrigan, a postdoctoral fellow at the
University of Florida.
The National Science Foundation and the Agouron Institute in
Pasadena, Calif. have supported this research.
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