Schwarz
View current page
...more recent posts
"What in Creation ?"
As per NYT 8/25 : Experiment Backs Novel Theory on Origin of Life, By NICHOLAS WADE
maverick theory about the origin of life has
received striking support from an experiment
that mimicked the violent interactions of deep
seated rock and common gases in the Hadean epoch,
the days when the earth had just formed as a planet.
Researchers found to their surprise that even in such
hellish conditions they had created a chemical that is
crucial for the metabolism of living cells.
The result is evocative because the chemical, known as
pyruvate, is a crucial component of living cells, being the fuel for a universal energy
producing process known as the citric acid cycle.
The new finding, reported in today's issue of Science by Dr. George D. Cody and his
colleagues at the Carnegie Institution of Washington's Geophysical Laboratory, does not
explain how or where life began but it supports a theory that proposes a new way of looking
at this long intractable problem.
The theory, proposed by a German patent attorney, Dr. Günther Wächtershäuser of Munich,
holds that the origin of life should be sought by looking for a metabolism, some repeated
cycle of chemical change, that could have taken place on the early earth and that could then
have built itself up into more complex molecules and organisms. This contrasts with the
conventional approach, which is to take familiar parts of today's cells, like nucleic acids, and
try to figure out the conditions in which they might have formed spontaneously.
Dr. Wächtershäuser dismisses the latter approach as the broth theory because even when a
researcher has found conditions under which the individual chemical ingredients of life might
have been formed, it is hard to explain why they should then assemble themselves into living
cells.
He calls his own proposal "the iron sulfur world theory" because he believes that metallic
surfaces, particularly that of the common mineral iron sulfide, would have been promising
facilitators, or catalysts, of the chemical reactions that created the precursor chemicals of
living cells.
It is unusual for amateurs, even a qualified chemist like Dr. Wächters häuser, to contribute to
the specialized worlds of modern science. And his ideas, being only theoretical, did not
arouse much enthusiasm until 1997 when he showed that an iron- sulphur surface could
promote the conversion of carbon monoxide to a two-carbon chemical important in
biochemistry of living cells.
To biochemists, his finding had particular resonance because at the center of many enzymes
are iron and sulfur atoms that transfer electrons in ways vital to the cell's energy
requirements.
The idea that living cells are elaborate codifications of some primitive chemical cycle that got
going on an iron-sulfur surface is to them not so alien.
Dr. Cody and colleagues at the Carnegie Institution decided to use a special high-pressure
apparatus they possessed to explore how Dr. Wächtershäuser's proposed system might work
at sites like the volcanic vents in the deep ocean. This kind of chemistry is a dangerous
pursuit, since at high pressures water becomes a violent acid and carbon monoxide eats
through steel.
"We set out to explore the ability of minerals to catalyse reactions that would be important in
a primitive metabolic sense," Dr. Cody said. Putting iron sulfur, a source of carbon
monoxide into their reaction tube, "We came across an unanticipated result," he said. That
was the formation of large amounts of pyruvate.
The tube also contained a hydrogen sulphide-like chemical to mimic the hydrogen sulfide
produced by volcanoes.
Pyruvate consists of three carbon atoms linked together and is an obvious building block
from which sugars and the other carbon-based molecules of life can be constructed.
Dr. Wächtershäuser believes the origin of life lies in autocatalysis, the emergence of some
natural chemical process, like the pyruvate-producing one, in which the products help the
reaction go faster.
"Evolution is better and better autocatalysis," he said in a phone interview yesterday.
If one of these autocatalytic processes started to generate the class of fatty chemicals known
as lipids, these might form a bubble round the system and the first cell would be generated.
The cell would have left the surface on which it was generated and later developed the
elaborate information-storage system embodied in today's DNA molecules.
Dr. Michael W.W. Adams, a biochemist who studies early life at the University of Georgia,
said Dr. Wächtershäuser had developed a very reasonable and testable hypothesis for the
origin of organic material relevant to life. "It makes so much sense to have metal catalysts
involved at the dawn of life," Dr. Adams said, "especially metal sulfides, because these are
essential to most energy conserving processes. I very much think he is on the right track."
In a written commentary on Dr. Cody's report, Dr. Wächtershäuser said that, with the
creation of pyruvate, all of the eight sequential steps needed to make peptides from carbon
monoxide had now been shown to be chemically possible. Peptides are short chains of
amino acids, the components of the protein molecules that are the workhorses of the living
cell.
The new results "greatly strengthen the hope that it may one day be possible to understand
and reconstruct the beginnings of life on earth," he wrote.