Posted on 10/23/2003 1:14:46 PM PDT by Mark Felton
Two of the crucial components for the origin of life - genetic material and cell membranes - could have been introduced to one another by a lump of clay, new experiments have shown.
The study of montmorillonite clay, by Martin Hanczyc, Shelly Fujikawa and Jack Szostak at the Massachusetts General Hospital in Boston, revealed it can sharply accelerate the formation of membranous fluid-filled sacs.
These vesicles also grow and undergo a simple form of division, giving them the properties of primitive cells. Previous work has shown that the same simple mineral can help assemble the genetic material RNA from simpler chemicals. "Interestingly, the clay also gets internalised in the vesicles," says Leslie Orgel, an origin of life expert at the Salk Institute for Biological Sciences in San Diego, California. "So this work is quite nice in that it finds a connection between the mechanism that creates RNA and encloses it in a membrane."
Inherit, mutate, evolve
The genesis of genetic material and the emergence of cell structure are hot areas of research, but until now the two had not connected. The birth of genetic material was clearly crucial for life to take on its unique abilities to inherit, mutate and evolve.
And membranes were key to the physiology of cells because they protect their contents, concentrate chemicals to promote reactions and isolate successful genes from unsuccessful ones. "It's clear you really need both these elements to get evolution off the ground and running," says Szostak.
Research has already shown that some of building blocks for RNA-like molecules and membranes are spontaneously created by chemical reactions in outer space and in conditions that may have existed on the primordial Earth. But how these subunits were then assembled is still debated.
For RNA, one popular theory revolves around the unusual properties of montmorillonite clay. The negatively charged layers of its crystals create a sandwich of positive charge between them. This turns out to be a highly attractive environment for RNA subunits to concentrate and join together into long chains.
100-fold acceleration
Szostak wondered whether montmorillonite could also help the assembly of vesicles from simple fatty acid precursors. He remembers the day his colleagues Hanczyc and Fujikawa ran into his office to show him their first results: the clay caused a 100-fold acceleration of vesicle formation.
"It was pretty amazing," he says. Once formed, the vesicles often incorporated bit of clay and were able to grow by absorbing more fatty acid subunits.
Subscribe to New Scientist for more news and features
Related Stories
Plasma blobs hint at new form of life 17 September 2003
Ponds, not oceans, the cradle of life 9 May 2002
Life's building blocks created in space simulator 27 March 2002
For more related stories search the print edition Archive
Weblinks
Jack Szostak, Massachusetts General Hospital
Leslie Orgel, Salk Institute for Biological Sciences
Origins of life, University of Arizona
Science
His team also showed the clay could hold RNA and form vesicles at the same time. Fluorescently-labelled RNA attached to the clay ended up assembled into vesicles after the reaction. And the researchers were able to get these "protocells" to divide by forcing them through small holes. This caused them to split into smaller vesicles, with minimal loss of their contents.
Szostak admits that in a natural setting the vesicles would rarely be forced to divide in this way. So now his group is searching for different mixtures of membrane-forming molecules that might divide spontaneously when they reach a certain size.
Journal reference: Science (vol 302, p 618 )
Philip Cohen
The Gumby creationists want to have a word with you.
"Darkness has fallen over Clay Land (tm). Not since Santa backed over Rudolph has there been such great misery in this normally overly-happy place. For the horrible has occurred. Sluggo and the Blockheads have joined forces.Sinister laughter can be heard from a dark house on the edges of Clay Land. Inside, a crowd is gathered in the basement. Pokey can be seen in the corner, strapped to a chair and gagged. Sluggo is looking into a large shoebox in the center of the room, an evil Grinch-like grin from ear-to-ear. He calls the Blockheads over and says that it's time to begin. They peer into the box...
In the middle of the box is Gumby, one wrist lashed to the wrist of his competitor, Mr. Bill. At one end of the box, imbedded in the cardboard, is a razorblade. At the other end, a Zippo (tm) lighter, specially designed so that either of the contestants can use it. Sluggo gives the signal to begin. Only one clay figure may emerge from the box alive. If it is Gumby, he and Pokey may go free; if it is Mr. Bill, Pokey is killed and Mr. Bill gets to drive off with Malibu Stacey (tm).
Is Mr. Bill shredded or Gumby melted? "
For the rest of the story: click here
Old Patriot
"So now his group is searching for different mixtures of membrane-forming molecules that might divide spontaneously when they reach a certain size."I expect it will be as mysterious as knowing the exact time when an atom "spontaneously" decides to emit a photon.
Under what conditions on the primative Earth did these reactions occur? What was the distribution of clay on that primative Earth? Was the atmosphere reducing? Was it oxidizing?. Or what is most probable; was it methane? Will that reaction go in a methane environment?? I have no idea. I suspect that the authors don't either.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.