http://www.resa.net/nasa/origins_life.htm#precursors
RNA World hypothesis: The first self-replicating compounds were bits of free-floating RNA that used ribosymes, rather than protein-based enzymes, to facilitate their replication. These self-replicating RNA strands eventually "moved in" to pre-existing protective envelopes (lipospheres, coacervates, or proteinoid microspheres) which were the forerunners of cell membranes. The path from self-replicating RNA strands to RNA strands that could control the synthesis of proteins is less clear.
RNA World hypothesis: The first self-replicating compounds were bits of free-floating RNA that used ribosymes, rather than protein-based enzymes, to facilitate their replication. These self-replicating RNA strands eventually "moved in" to pre-existing protective envelopes (lipospheres, coacervates, or proteinoid microspheres) which were the forerunners of cell membranes. The path from self-replicating RNA strands to RNA strands that could control the synthesis of proteins is less clear.
pgwenthold
Penultimate Amazing
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There was a great proposal just a couple of years ago that suggests the following:
Hydrophobic petroleum-based aerosols are created by ocean spray. Recall that organic material will float on the water, and the action of the waves gets them airborne. This is a known phenomenon that occurs today.
In the atmosphere, the surfaces of the aerosols become oxidized in the reaction with hydroxyl radicals. This turns the surface of the aerosol into hydrophilic alcohols and carboxylic acids. Hydroxy radicals abstract hydrogens creating organic radicals, which then react with oxygen to create peroxy radicals, which then undergo further reaction to create the oxidized species.
The aerosols eventually settle back into the water, but now with their hydrophilic surface, i.e. the lipid layer, they are capable of dissolving in water.
Now, there are certain concerns. For example, in order for this to work, the aerosol has to be small enough to fly for a sufficiently long time to get the surface oxidized, but large enough to eventually fall back to the ground without evaporating away. Amazingly, it is calculated that the size of aerosols needed for this to work just happen to be the same size as cells. Coincidence? Maybe, but then again...
This proposal was published in the Proceedings of the National Academy a couple of years ago.
I like it a lot, but then, I am biased. See, the proposal did not come from biologists or RNA experts or anything like that, it came from a bunch of geeky chemical physicists (and one physical organic chemist) at the University of Colorado who study aerosols. That physical organic chemist, the one who provides the chemical reactivity insight, is a good buddy of mine.
Now, this idea hasn't gone over so well, but not because it isn't sound. The biologists have been highly offended by the idea that the origins of cells may not be solution biochemistry, but in the atmosphere. In fact, my friend tells me that on at least one occasion when presenting this material (usually in a chemistry seminar), biologists have read a formal statement objecting to the fact that this work is being done by chemists and not biologists. Unfortunately, they don't know enough chemical physics to object to the science.
Hydrophobic petroleum-based aerosols are created by ocean spray. Recall that organic material will float on the water, and the action of the waves gets them airborne. This is a known phenomenon that occurs today.
In the atmosphere, the surfaces of the aerosols become oxidized in the reaction with hydroxyl radicals. This turns the surface of the aerosol into hydrophilic alcohols and carboxylic acids. Hydroxy radicals abstract hydrogens creating organic radicals, which then react with oxygen to create peroxy radicals, which then undergo further reaction to create the oxidized species.
The aerosols eventually settle back into the water, but now with their hydrophilic surface, i.e. the lipid layer, they are capable of dissolving in water.
Now, there are certain concerns. For example, in order for this to work, the aerosol has to be small enough to fly for a sufficiently long time to get the surface oxidized, but large enough to eventually fall back to the ground without evaporating away. Amazingly, it is calculated that the size of aerosols needed for this to work just happen to be the same size as cells. Coincidence? Maybe, but then again...
This proposal was published in the Proceedings of the National Academy a couple of years ago.
I like it a lot, but then, I am biased. See, the proposal did not come from biologists or RNA experts or anything like that, it came from a bunch of geeky chemical physicists (and one physical organic chemist) at the University of Colorado who study aerosols. That physical organic chemist, the one who provides the chemical reactivity insight, is a good buddy of mine.
Now, this idea hasn't gone over so well, but not because it isn't sound. The biologists have been highly offended by the idea that the origins of cells may not be solution biochemistry, but in the atmosphere. In fact, my friend tells me that on at least one occasion when presenting this material (usually in a chemistry seminar), biologists have read a formal statement objecting to the fact that this work is being done by chemists and not biologists. Unfortunately, they don't know enough chemical physics to object to the science.
Bottle or the Gun
Muse
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That was in my sig....only not so wordy.
Ian Stewart's book Life's other secret includes a good and fairly concise explanation of the main theories of how cells first came about that even a layman like me was able to understand.
Of course there is: A good teacher.CFLarsen said:
I'll try my best to be one by suggesting a few links:
Synthesis of complex molecules in space. (Kuzicheva EA & Gontareva NB,1999. The possibility of nucleotide abiogenetic synthesis in conditions of 'KOSMOS-2044' satellite space flight. Advances in Space Research 23(2): 393-396.)( Schueller,Gretel, 1998 (12 Sep.). Stuff of Life. New Scientist, http://www.newscientist.com/hottopics/astrobiology/stuffof.jsp)
Research into molecule formation in different atmospheres. (http://talkorigins.org/indexcc/CB/CB035.html)
Synthesis of constituents in the "iron-sulfur" world around hydrothermal vents. (Cody, GD et al.,2000. Primordial carbonylated iron-sulfur compounds and the synthesis of pyruvate. Science 289:1337-1340.)( Russell, M.J. and Hall, A.J., 1997. Theemergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and pH front. Journal of the Geological Society of London154: 377-402.)( Russell M.J., Hall A.J., Daia D, Turner D. and Rahman L.,1997. The emergence of life from iron sulphide compartments at a submarine hydrothermal redox and pHfront. http://www.gla.ac.uk/projects/originoflife/html/2001/pdf_files/Russell_&_Hall.pdf)
Paul C. Anagnostopoulos
Nap, interrupted.
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You made this part up, right? This sounds like some kind of horror story out of a science-is-close-minded-dogma tract.
~~ Paul
pgwenthold
Penultimate Amazing
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Paul C. Anagnostopoulos said:
I'm not making it up, but I am more careful in my interpretation. For example, their objection could be on the grounds that by treating only within chemistry, they aren't utilizing the expertise that other fields might provide, and may be saying things that are either well known or known to be not true in other fields. There would be merit to that argument.