Posted on 09/03/2004 6:49:50 AM PDT by PatrickHenry
Howard Hughes Medical Institute researchers are proposing that the first battle for survival-of-the-fittest might have played out as a simple physical duel between fatty bubbles stuffed with genetic material. The scientists suggest that genetic material that replicated quickly may have been all the bubbles needed to edge out their competitors and begin evolving into more sophisticated cells.
This possibility, revealed by laboratory experiments with artificial fatty acid sacs, is in sharp contrast to a current theory of the earliest evolution of cells, which suggests that cellular evolution was driven by primordial genetic machinery that actively synthesized cell membranes or otherwise influenced cell stability or division.
The researchers, led by Howard Hughes Medical Institute investigator Jack W. Szostak, published their findings in the September 3, 2004, issue of the journal Science. Szostak and first author Irene Chen, both from Massachusetts General Hospital and Harvard Medical School, collaborated on the studies with Richard Roberts of the California Institute of Technology.
Cells are basically sacs encapsulated by bilayered membranes of fatty acids and other lipids, plus proteins. A central question in evolution is how simple versions of these cells, or vesicles, first arose and began the process of competition that drove the evolution of life.
"Most of the previous thinking about how cells grew and evolved was based on the idea of the initial evolution of structural RNAs or ribozymes -- enzymes that could synthesize membrane molecules," said Szostak. The ribozymes might have made more membrane material while the structural RNAs might have formed a cytoskeleton that influenced stability, shape, growth or division, he said. However, Szostak and his colleagues theorized that a far simpler physical process might explain why cells would compete with one another for the materials necessary to expand their size.
"We proposed that the genetic material could drive the growth of cells just by virtue of being there," he said. "As the RNA exerts an osmotic pressure on the inside of these little membrane vesicles, this internal pressure puts a tension on the membrane, which tries to expand. We proposed that it could do so through the spontaneous transfer of material from other vesicles nearby that have less internal pressure because they have less genetic material inside."
In order to test their theory, the researchers first constructed simple model "protocells," in which they filled fatty-acid vesicles with either a sucrose solution or the same solvent without sucrose. The sucrose solution created a greater osmotic pressure inside the vesicles than the solvent alone. The membranes of the simple vesicles were not as sophisticated as the membranes of today's living cells, said Szostak. However, they closely resembled the kinds of primordial vesicles that might have existed at the beginning of evolution.
When the scientists mixed the two vesicles, they observed that the ones with sucrose - in which there was greater membrane tension - did, indeed, grow by drawing membrane material from those without sucrose.
"Once we had some understanding that this process worked, we moved on to more interesting versions, in which we loaded the vesicles with genetic molecules," said Szostak. The researchers conducted the same competition tests using vesicles loaded with the basic molecular building blocks of genetic material, called nucleotides. Next, they used RNA segments, and finally a large, natural RNA molecule. In all cases, they saw that the vesicles swollen with genetic material grew, while those with no genetic material shrank.
It is important to note, said Szostak, the concentrations of genetic material that his group used were comparable to those found in living cells.
"In contrast to the earlier idea that Darwinian competition at the cellular level had to wait until the evolution of lipid-synthesizing ribozymes or structural RNAs, our results show that all you would need is to have the RNA replicating," said Szostak. "The cells that had RNA that replicated better -- and ended up with more RNA inside -- would grow faster. So, there is a direct coupling between how well the RNA replicates and how quickly the cell can grow. It's just based on a physical principle and would emerge spontaneously," he said.
According to Szostak, the next step in the research will depend on another major effort under way in his laboratory to create artificial, replicating RNA molecules.
"If we can get self-replicating RNAs, then we can put them into these simple membrane compartments and hope to actually see this competitive process of growth that we are hypothesizing," he said.
Vesicles encapsulating sucrose.
Fatty acid vesicles were prepared from oleic acid and myristoleic acid as described (S1), at a concentration of 40-80 mM. All fatty acids and fatty acid derivatives were obtained from Nu-chek Prep, Inc, Elysian, MN. POPC (Avanti Polar Lipids, Inc.; Alabaster, AL) vesicles were prepared by rotary evaporation of a stock POPC/chloroform solution followed by resuspension of the thin film and five freeze-thaw cycles. Low osmolarity vesicles were obtained by resuspension in 0.2 M bicine, pH 8.5, titrated with NaOH. For oleic acid and POPC, high osmolarity vesicles were obtained by resuspension in 1 M sucrose, 0.2 M bicine, pH 8.5. For myristoleic acid, high osmolarity vesicles were obtained by resuspension in 0.5 M sucrose, 0.2 M bicine, pH 8.5, because lysis was determined to occur at a lower applied osmotic gradient. Dilutions of myristoleate vesicles were made using buffers containing myristoleate at the critical aggregate concentration (cac = 4 mM) (S2), to avoid dissolution of the vesicles. The cac of oleate vesicles is much lower than the experimental concentrations (~80 µM) (S1). Vesicle preparations were extruded through 100 nm polycarbonate filters using the Mini- Extruder system (Avanti Polar Lipids, Inc.). If necessary, vesicles were purified from unencapsulated solutes by size-exclusion chromatography.
You wrote:
"The interesting part is that they seem to start 'eating' spontanously at a very early stage. Next stage is getting them to split and reproduce. All with nothing more than a few common chemicals and energy. Before you know it (well, billions of years) you have bacteria, plants, animals, people. "
[Asbestos suit DONNED.]
All this does is to (finally) flesh out details of the model concerning development of cellular life. Getting a time machine to independently verify the model is the hard part </g>
You and every other psychotic in the world.
You and every other psychotic in the world.
WRONG
No, that was a true statement. Listen to the voices in your head and find one that agrees.
I am very sorry to inform you sir
but YOU are the one with the voices.
Accepting Jesus Christ as your personal savior does not mean you have to take Genesis literally. It can be read figuratively without obviating the meaning of Scripture.
Given that you've already made it clear -- by way of cutting the comments of other people out of context -- that you are willing to use lies to support your agenda, why should I believe anything that you tell me?
Has nothing to do with the theory of evlution.
I still say you ought to go back and actually read my post #49 before calling it BS.
OK I read it three times.
Now this IS a "fact"
"In the begining God created the heavens and the earth"
and eveerything else.
Do you think Jesus of Nazareth is about to re-appear one day ?
i.e Are you a Christian that believes in the second coming ?
You wrote...
"In science, theories do not turn into facts through the accumulation of evidence. Rather, theories are the end points of science. They are understandings that develop from extensive observation, experimentation, and creative reflection. They incorporate a large body of scientific facts, laws, tested hypotheses, and logical inferences. In this sense, evolution is one of the strongest and most useful scientific theories we have."
I am also a true scientist. My fields of expertise are : Consciousness; History; Geography; Politics; Comparative Religion; Childhood; Memory; The Study of Trauma; and others. Age is not wisdom. Life experience is.
What if someone came along and using the scientific method, i.e Extensive observation, experimentation, replicability, creative reflection, facts, tested hypotheses, logical inferences etc. they could prove that there was a higher force in the universe that was benevolent, stable, ordered and expansive ?
What if this same person could also prove what happened with Moses was divinely guided and that a higher force intervenes in the history of humankind ?
Would this person's testimony blow your socks off ?
Or would you continue to wear the old, smelly socks of materialistic evolution ?
;-)
To the crank, it's the ultimate counter argument to any assertion. If you assert "X," your interlocutor simply says: "'X' is BS!" and what can you say? How can you rebut a content-free rebuttal?
You can't; that's what makes it so appealing to cranks and mental defectives. It gives them the illusion of victory over the ideological windmills that threaten their fragile, brittle world view, without having to invest a scintilla of knowledge or logic in their argument.
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