Transition metal catalysts could be key to origin of life, scientists report

Sep 03, 2010
Ferric citrate is a structure formed from the transition metal iron and citrate, a compound produced by plants, algae, and many bacteria. Morowitz and his colleagues propose that structures like this could have catalyzed the formation of molecular building blocks, leading ultimately to the formation of complex molecules essential for the origin of life. Credit: Harold Morowitz, George Mason University

One of the big, unsolved problems in explaining how life arose on Earth is a chicken-and-egg paradox: How could the basic biochemicals -- such as amino acids and nucleotides -- have arisen before the biological catalysts (proteins or ribozymes) existed to carry out their formation?

In a paper appearing in the current issue of The Biological Bulletin, scientists propose that a third type of catalyst could have jumpstarted metabolism and life itself, deep in hydrothermal ocean vents.

According to the scientists' model, which is experimentally testable, involving transition metal elements (iron, copper, nickel, etc.) and ligands (small ) could have catalyzed the synthesis of basic biochemicals () that acted as building blocks for more complex molecules, leading ultimately to the . The model has been put forth by Harold Morowitz of George Mason University (GMU), Vijayasarathy Srinivasan of GMU, and Eric Smith of the Santa Fe Institute.

"There has been a big problem in the origin of life (theory) for the last 50 years in that you need large to be catalysts to make monomers, but you need monomers to make the catalysts," Morowitz says. However, he suggests, "You can start out with these small metal-ligand catalysts, and they'll build up the monomers that can be used to make the (large protein catalysts)."

A transition metal atom can act as the core of a metal-ligand complex, in which it is bound to and surrounded by other ligands. Morowitz and his colleagues propose that simple transition metal-ligand complexes in hydrothermal ocean vents catalyzed reactions that gave rise to more complex molecules. These increasingly complex molecules then acted as ligands in increasingly efficient transition metal-ligand complex catalysts. Gradually, the basic molecular ingredients of metabolism accumulated and were able to self-organize into networks of chemical reactions that laid the foundation for life.

"We used to think if we could understand what carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur were doing, we would immediately be able to understand biology," Morowitz says, listing elements that constitute a large proportion of Earth's biomass. "But now we're finding that these other fairly rare elements, transition metals, are necessary in biology, so we ask, 'What was their role in the origin of life?'"

The proposal suggests that the rise of life forms is a natural consequence of the unique properties of transition metals and ligand field theory, which describes the characteristics of ligand complexes.

"The idea has emerged from a study of the periodic table. We strongly feel that unless you're able to see how life comes about in some formal chemical way, you're never really going to solve the problem," Morowitz says.

Morowitz and his colleagues are preparing experiments to test the catalytic properties of transition metal-ligand complexes built with different types of ligands. Ligands known to bind tightly to transition metals include molecules produced during the course of the reductive citric acid cycle, a series of biochemical reactions essential for many microorganisms.

"We think life probably began with the reductive citric acid cycle, and there is evidence that under hydrothermal vent conditions some of the cycle's intermediates form," Morowitz says. "We are going to start with these molecules and mix them with various transition metals, cook them at different temperatures for a while, and see what kinds of catalysts we've made."

Such experiments could reveal what kinds of catalytic reactions took place to lay the foundations for life. The hypothesis also allows for the possibility that life could have arisen more than once.

"Life could have originated multiples times, and, if we find life elsewhere in the universe, it could be very similar to the life we know here because it will be based on the same and ligands," Morowitz says. "It's a conjecture at the moment, but it could become a formal scientific core for the emergence of ."

Explore further: Four billion-year-old chemistry in cells today

More information: Morowitz, H. J., Srinivasan, V., Smith, E. (2010) Ligand Field Theory and the Origin of Life as an Emergent Feature of the Periodic Table of Elements. Biol. Bull. 219: 1-6.

Provided by Marine Biological Laboratory

4.5 /5 (23 votes)

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DamienS
4.7 / 5 (3) Sep 03, 2010
I love this type of research. I refer others that also have a fascination with the origin of life, to this paper:
http://www.americ...-of-life

From the link:
we present a view gaining attention in the origin-of-life community that takes the question out of the hatchery and places it squarely in the realm of accessible, plausible chemistry. As we see it, the early steps on the way to life are an inevitable, incremental result of the operation of the laws of chemistry and physics operating under the conditions that existed on the early Earth, a result that can be understood in terms of known laws of nature. As such, the early stages in the emergence of life are no more surprising, no more accidental, than water flowing downhill.
Pratyeka
not rated yet Sep 04, 2010
At long last, a simple and elegant rational process for the origin of life, arrived at by detailed logical analysis of facts.
ggg
5 / 5 (1) Sep 04, 2010
'proposal' 'suggests' When they can recreate the automatic spontaneous generation of life origin then lets give them some credit at that time, please! We can't even build the simplest life from scratch by hand; yet are already patting ourselves on the back..
hylozoic
1 / 5 (1) Sep 04, 2010
Countin' angels on pins? Bwahahahahaha!
If it's Occam's razor then Panspermia is Swayze at the door.
And that's Science
for any occasion!
kevinrtrs
1 / 5 (3) Sep 06, 2010
Sigh....when willlll life spontaneously occur?

I suggested last week that first we have to show that a simple pin-needle can be constructed spontaneously by random physical events with no interference from intelligent agents like scientists BEFORE we even begin to consider something as complex as the cell.

Those wishing to have life arise spontaneously stubbornly and consistently refuse to look into and consider the incredible complexity in even the simplest of cells. Sure, they understand the isolated parts that hundreds of scientists [biologists etc.] been able to unravel so far, but they simply refuse to consider the complex systematic requirements that make up what we call life in a cell.
This kind of persistence arise from a pre-determined belief that there is no creator.
I suppose those who disagree will be able to say the same for me - in the opposite direction!
How about we go and 1st build our OWN simplest life form from scratch so we can appreciate the complexity involved?
Skeptic_Heretic
3 / 5 (2) Sep 07, 2010
I suggested last week that first we have to show that a simple pin-needle can be constructed spontaneously by random physical events with no interference from intelligent agents like scientists BEFORE we even begin to consider something as complex as the cell.
There is no natural affinity in your argument, as such, your argument is junk. Just like I told you when you first posted this.
Those wishing to have life arise spontaneously stubbornly and consistently refuse to look into and consider the incredible complexity in even the simplest of cells.

Secondly, cells wouldn't come into existence in the same construction or manner in which they exist today.
bowerp
not rated yet Sep 19, 2010
I am not sure about the point of this arguement. I have read in books such as the selfish gene that it is plausible that monomers such as amino acids and RNA could spontaneously form from compounds such as CO2, NH3, H20 etc if under the right conditions. So why the need for another catalyst?