ASU researcher may have discovered key to life before its origin on Earth

February 28, 2008

An important discovery has been made with respect to the mystery of “handedness” in biomolecules. Researchers led by Sandra Pizzarello, a research professor at Arizona State University, found that some of the possible abiotic precursors to the origin of life on Earth have been shown to carry “handedness” in a larger number than previously thought.

The work is being published in this week’s Early Edition of the Proceedings of the National Academy of Sciences. The paper is titled, “Molecular asymmetry in extraterrestrial chemistry: Insights from a pristine meteorite,” and is co-authored by Pizzarello and Yongsong Huang and Marcelo Alexandre, of Brown University.

Pizzarello, in ASU’s Department of Chemistry and Biochemistry, worked with Huang and Alexandre in studying the organic materials of a special group of meteorites that contain among a variety of compounds, amino acids that have identical counterparts in terrestrial biomolecules. These meteorites are fragments of asteroids that are about the same age as the solar system (roughly 4.5 billion years.)

Scientists have long known that most compounds in living things exist in mirror-image forms. The two forms are like hands; one is a mirror reflection of the other. They are different, cannot be superimposed, yet identical in their parts.

When scientists synthesize these molecules in the laboratory, half of a sample turns out to be “left-handed” and the other half “right-handed.” But amino acids, which are the building blocks of terrestrial proteins, are all “left-handed,” while the sugars of DNA and RNA are “right-handed.” The mystery as to why this is the case, “parallels in many of its queries those that surround the origin of life,” said Pizzarello.

Years ago Pizzarello and ASU professor emeritus John Cronin analyzed amino acids from the Murchison meteorite (which landed in Australia in 1969) that were unknown on Earth, hence solving the problem of any contamination. They discovered a preponderance of “left-handed” amino acids over their “right-handed” form.

“The findings of Cronin and Pizzarello are probably the first demonstration that there may be natural processes in the cosmos that generate a preferred amino acid handedness,” Jeffrey Bada of the Scripps Institution of Oceanography, La Jolla, Calif., said at the time.

The new PNAS work was made possible by the finding in Antarctica of an exceptionally pristine meteorite. Antarctic ices are good “curators” of meteorites. After a meteorite falls -- and meteorites have been falling throughout the history of Earth -- it is quickly covered by snow and buried in the ice. Because these ices are in constant motion, when they come to a mountain, they will flow over the hill and bring meteorites to the surface.

“Thanks to the pristine nature of this meteorite, we were able to demonstrate that other extraterrestrial amino acids carry the left-handed excesses in meteorites and, above all, that these excesses appear to signify that their precursor molecules, the aldehydes, also carried such excesses,” Pizzarello said. “In other words, a molecular trait that defines life seems to have broader distribution as well as a long cosmic lineage.”

“This study may provide an important clue to the origin of molecular asymmetry,” added Brown associate professor and co-author Huang.

Source: Arizona State University

Explore further: NASA renews search for antarctic meteorites

Related Stories

NASA renews search for antarctic meteorites

November 16, 2016

Three federal entities, including NASA, are reaffirming their commitment to search for Antarctic meteorites, to help learn more about the primitive building blocks of the solar system and answer questions about Earth's neighbors ...

Did 40-year-old Viking experiment discover life on Mars?

October 21, 2016

(Phys.org)—In 1976, two Viking landers became the first US spacecraft from Earth to touch down on Mars. They took the first high-resolution images of the planet, surveyed the planet's geographical features, and analyzed ...

Shooting Meteorites in a Barrel

February 26, 2010

High-impact lab experiments simulate whether the building blocks of life could have survived the rough arrival on Earth via meteorite impact.

Meteorites reveal another way to make life's components

March 9, 2012

(PhysOrg.com) -- Creating some of life's building blocks in space may be a bit like making a sandwich – you can make them cold or hot, according to new NASA research. This evidence that there is more than one way to ...

Meteorite impacts can create DNA building blocks

August 18, 2015

A new study shown that meteorite impacts on ancient oceans may have created nucleobases and amino acids. Researchers from Tohoku University, National Institute for Materials Science and Hiroshima University discovered this ...

Amino acid alphabet soup

August 19, 2011

All life on Earth relies on a standard set of 20 amino acids to build the proteins that carry out life's essential actions. But did it have to be this way?

Recommended for you

Samsung to disable Note 7 phones in recall effort

December 9, 2016

Samsung announced Friday it would disable its Galaxy Note 7 smartphones in the US market to force remaining owners to stop using the devices, which were recalled for safety reasons.

Cow gene study shows why most clones fail

December 9, 2016

It has been 20 years since Dolly the sheep was successfully cloned in Scotland, but cloning mammals remains a challenge. A new study by researchers from the U.S. and France of gene expression in developing clones now shows ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

out7x
1.3 / 5 (4) Feb 29, 2008
Molecular asymmetry is due to electron orbital configurations. Nothing new here.
Ragtime
Mar 29, 2008
This comment has been removed by a moderator.
HenisDov
not rated yet Mar 30, 2008
Chirality In Life Still Awaits Elucidation

A. From "...key to life before its origin on Earth?"
http://www.physor...html#tab

When scientists synthesize these molecules in the laboratory, half of a sample turns out to be left-handed and the other half right-handed. But the amino acids that are the building blocks of terrestrial proteins are all left-handed, while the sugars of DNA and RNA are right-handed. The mystery as to why this is the case, parallels in many of its queries those that surround the origin of life...

Thanks to the pristine nature of this meteorite, we were able to demonstrate that other extraterrestrial amino acids carry the left-handed excesses in meteorites and, above all, that these excesses appear to signify that their precursor molecules, the aldehydes, also carried such excesses, Pizzarello said. other words, a molecular trait that defines life seems to have broader distribution as well as a long cosmic lineage.

B. From "Allosteric, chiral-selective drug binding to DNA"
http://www.pnas.o...2032.pdf

(Allosteric: of, relating to, undergoing, or being a change in the shape and activity of a protein, as an enzyme, that results from combination with another substance at a point other than the chemically active site)

DNA is polymorphic and exists in a variety of distinct conformations. Duplex DNA can adopt a variety of sequence-dependent secondary structures that range from the canonical right-handed B form through the left-handed Z conformation. Multistranded triplex and tetraplex structures are now known to exist. All of these unique conformations may play important functional roles in gene expression.

C. Chirality in life still awaits elucidation

First, reasearch findings should be stated scientifically correctly. In A above NOT "a molecular trait that defines life seems to have broader distribution as well as a long cosmic lineage%u201D, but YES "a molecular conformation dominant in Earth life may have broader distribution and additional cosmic presence.

Next, re in A above "the mystery as to why this is the case":

My conjecture about the probable reasons for the prevailing chirality:

Darwinian evolution started at life's day one, with the genesis of the first organisms, the replicating oligomers, pre-archaea genes. It started under yet-unknown energetic conditions, by a serendipitous accident, with oligomeric (RNA?) conformations, in a soup containing all their essential molecular progenitors. These Conformations happened to absorb the amounts of energy enabling their polymerization, to lengths precipitated as determined by the nature and conditions of the soup.

The sugars and the nitrogen-based compounds that, together with the phosphates, are the components of the genes-organisms, are chiral. There probably is an energetic advantage in homochirality and chiral homogeneity for the self-replication of biopolymers.

This serendipitous accident set up a matrix-field of energy with a potential extended between its source, the sun radiation and the precipitating organisms. This was the genesis of the ongoing formation and maintenance of Earth's biosphere.

And since the biosphere started it could only evolve in more favorable energetic directions and towards stabler components. Survival. After all this is evolution.

But this is a conjecture. Chirality in life still awaits elucidation...


Dov Henis
HenisDov
not rated yet Mar 30, 2008
Chirality In Life Still Awaits Elucidation

A. From "...key to life before its origin on Earth?"
http://www.physor...html#tab

When scientists synthesize these molecules in the laboratory, half of a sample turns out to be %u201Cleft-handed%u201D and the other half %u201Cright-handed.%u201D But the amino acids that are the building blocks of terrestrial proteins are all %u201Cleft-handed,%u201D while the sugars of DNA and RNA are %u201Cright-handed.%u201D The mystery as to why this is the case, %u201Cparallels in many of its queries those that surround the origin of life...%u201D

Thanks to the pristine nature of this meteorite, we were able to demonstrate that other extraterrestrial amino acids carry the left-handed excesses in meteorites and, above all, that these excesses appear to signify that their precursor molecules, the aldehydes, also carried such excesses,%u201D Pizzarello said. %u201CIn other words, a molecular trait that defines life seems to have broader distribution as well as a long cosmic lineage.%u201D

B. From "Allosteric, chiral-selective drug binding to DNA"
http://www.pnas.o...2032.pdf

(Allosteric: of, relating to, undergoing, or being a change in the shape and activity of a protein, as an enzyme, that results from combination with another substance at a point other than the chemically active site)

DNA is polymorphic and exists in a variety of distinct conformations. Duplex DNA can adopt a variety of sequence-dependent secondary structures that range from the canonical right-handed B form through the left-handed Z conformation. Multistranded triplex and tetraplex structures are now known to exist. All of these unique conformations may play important functional roles in gene expression.

C. Chirality in life still awaits elucidation

First, reasearch findings should be stated scientifically correctly. In A above NOT "a molecular trait that defines life seems to have broader distribution as well as a long cosmic lineage%u201D, but YES "a molecular conformation dominant in Earth life may have broader distribution and additional cosmic presence.%u201D

Next, re in A above "the mystery as to why this is the case":

My conjecture about the probable reasons for the prevailing chirality:

Darwinian evolution started at life's day one, with the genesis of the first organisms, the replicating oligomers, pre-archaea genes. It started under yet-unknown energetic conditions, by a serendipitous accident, with oligomeric (RNA?) conformations, in a soup containing all their essential molecular progenitors. These Conformations happened to absorb the amounts of energy enabling their polymerization, to lengths precipitated as determined by the nature and conditions of the soup.

The sugars and the nitrogen-based compounds that, together with the phosphates, are the components of the genes-organisms, are chiral. There probably is an energetic advantage in homochirality and chiral homogeneity for the self-replication of biopolymers.

This serendipitous accident set up a matrix-field of energy with a potential extended between its source, the sun radiation and the precipitating organisms. This was the genesis of the ongoing formation and maintenance of Earth's biosphere.

And since the biosphere started it could only evolve in more favorable energetic directions and towards stabler components. Survival. After all this is evolution.

But this is a conjecture. Chirality in life still awaits elucidation...


Dov Henis

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.