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New evolutionary rethink?

VDOG

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nope this ain't a creation article.

this is from discover magazine, sorry if this is older article
_____________________________
The Soak-and-Bake Origin of Life

Armen Mulkidjanian, A biophysicist at Osnbaruck University in Germany, is rethinking the standard story of how life appeared on Earth. Many of his colleagues have assumed life originated in water; he places it on a dry mudflat. And whereas generally reasearchers generally regard ultraviolet rays from the sun as a threat to early biochemical reaction, Mulkidjanian argues that those rays gave life an essential jump start.
Despite his divergent conclusions, Mulkidjanian starts with a standard scenario that simple molecules on the young Earth developed into sugar phosphates and nitrogen bases, which in turn combined to form RNA-the first self-replication molecule. In a series of computer models, he and his colleagues find that RNA-like molecules withstand hards ultraviolet exposure better than sugar phosphates alone because attached nitrogen bases protech the molecules from UV damage. Extended RNA chains, known as polymers, are more stable still. The results suggest that ultraviolet rays would have selected for larger, more complex RNA molecules."People have been able to explain how the first polymers could build up on the primordial Earth. This work suggests a way out," Mulkidjanian says.
The reactions that piece together long RNA chains do not work well in the presence of water, Mulkidjanian realized. If he is correct, the steps that set the stage of life must of occured on a parched or semidry landscape."Once you get something more complex, like the first cell, you need water. Cells need water to survive,"he says. Tiday falts might have offered the ideal conditions, alternately soaking and baking organic molecules untile life emerged.
 

ThePhoenix

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Cool we can leave creationism totally out of this.

How does he explain the survival of early organic molecules under the punishing UV bombardment? Most experiments indicate that they would die, in fact UV bombardment is commonly used to kill bacteria.

Also, how does he explain the gathering of the chemicals? The best explaination I've heard is that polarized crystals attracted the molecules. That would provide a mechanism for the seperation of left handed and right handed amino acids. How does the mudflat theory explain that as well?
 
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LorentzHA

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ThePhoenix said:
How does he explain the survival of early organic molecules under the punishing UV bombardment? Most experiments indicate that they would die, in fact UV bombardment is commonly used to kill bacteria.
I was hoping someone would bring this up. Well done. That is another pat on the back for evolution. DNA from very simple organisms (Prokaryotic DNA) is curled over on itself as a defense mechanism from intense UV light. The DNA that is part of who we are is belioeved to have evolved from this DNA.

Interestingly enough several rocks from Mars that landed on the South Pole were found to have what appears to be fossilized prokaryotic DNA. Mars has very little atmoshphere so its DNA or precursor to life would naturally have to take on this "curl" for protective measure. That is one of the stumbling blocks creationist run into without even knowing it. DNA in the the double Helix cannot withstand intense amounts of UV light.
 
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lucaspa

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ThePhoenix said:
Cool we can leave creationism totally out of this.

How does he explain the survival of early organic molecules under the punishing UV bombardment? Most experiments indicate that they would die, in fact UV bombardment is commonly used to kill bacteria.
But that is at a much higher intensity than that found outside. And it is not the organic molecules which break down, but the cell that is killed. In this case the UV helps oxidation of lipids in the cell membrane to rupture the membrane. In an atmosphere of low oxygen, this would be much less likely to happen.

Proteins are not affected much by UV. In fact, I've used UV to sterilize dry proteins and still keep the activity of the protein.

Now, the original article reported in the OP says that having RNA protects the molecule from UV. The longer the chain, the more protection. So your question was answered to begin with. The whole point is that making polymers of ribonucleotides protects them from UV.

Also, how does he explain the gathering of the chemicals? The best explaination I've heard is that polarized crystals attracted the molecules. That would provide a mechanism for the seperation of left handed and right handed amino acids. How does the mudflat theory explain that as well?
The chemicals are concentrated in the mudflat theory by evaporation. Take a tidal pool and evaporate the water. Concentrates the chemicals in it infinitely.

This doesn't explain chirality. But that isn't important at this stage. You dont' have to start out with chirality; it can develop later. With RNA the problem isn't as acute, since the bases aren't chiral. The sugar ribose is, but it isn't going to matter much which enantiomer of the 5 carbon sugar you have since the interaction and activity is with the non-chiral bases.
 
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lucaspa

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VDOG said:
"In a series of computer models, he and his colleagues find that RNA-like molecules withstand hards ultraviolet exposure better than sugar phosphates alone because attached nitrogen bases protech the molecules from UV damage. Extended RNA chains, known as polymers, are more stable still. The results suggest that ultraviolet rays would have selected for larger, more complex RNA molecules.
This is the protection from UV.

Cells need water to survive,"he says. Tiday falts might have offered the ideal conditions, alternately soaking and baking organic molecules untile life emerged.
The protein-first theory of abiogenesis also makes use of tidal pools. In this the amino acids are dried in the tidal pool and undergo thermal polymerization to form proteins. When the tide comes back in the thermal proteins spontaneously form cells.

Put that together with this and you have the first cells with both proteins and RNA. That would mean not an RNA World or protein-first alone, but a combination of RNA and protein from the beginning.
 
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lucaspa

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ThePhoenix said:
Is the effect of oxygen on early organic molecules negligable, or does it attack them?
Depends on the molecule. Oxygen doesn't attack methane, for example. Oh, yes, methane will combust, but oxygen doesn't "attack" it as reacting with it outside combustion.

This may be too simple or too complex. Let me know if I've lost you or oversimplified:

Lipids are made from fatty acids. Fatty acids long chain molecules of carbon and hydrogen with a "head" that is a carboxylic acid (COOH). So, you can have octanoic acid. This is basically octane (gasoline) with a COOH group on one end. The common fatty acids in lipids have 16 or 18 carbons instead of the 8 of octanoic acid.

Now, many fatty acids are "unsaturated". This means that they have double bonds (C=C) between carbons instead of single bonds (C-C). Now, what can happen is that oxygen will attack the double bond, breaking it to form a single bond with an -OH group attached to one of the carbons.

Now, fatty acids make up lipids. Lipids are usually a glycerol with 2 fatty acids bound to it. Glyeros is 3 carbons each with an OH group attached. Since OH groups mean "alcohol", think of it as an ultimate alchohol. The COOH group reacts with the OH groups to form an ester bond ................. C-O-C
..........................ll
..........................O
The other OH group on glycerol has a phosphate group attached.

What this means is that lipids have a water-soluble end -- the phosphate group -- and a water-hating end: the fatty acid tails.

Thus, membranes have a bilayer of lipids. Two lipids with their water-hating tails together and the water soluble heads outward.

Now, if enough of those double bonds get turned to alcohol, those water-hating tails aren't water-hating anymore. So the membrane loses the bilayer and big holes open in it, letting everything inside the cell out.

UV light will also, by itself, break double bonds. Do enough of that and the tails fall apart and the membrane again falls apart.

DNA and proteins love UV light. That's how we know how much DNA or protein is present: shine UV light on it and see how much is absorbed! But they don't break.
 
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lucaspa

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VDOG said:
I'd like to give a reply, but since I lack knowledge of any science, I can't. All I did was copy this article from discover magazine 2003.
Sorry. O btw, I made some minor spelling mistakes, when writing that article.

thanks for pointing out this info Lucaspa.
What reply would you like to make.

VDOG, there are a couple of theories of abiogenesis out there. One is the RNA World. It is the most popular right now. This guy is modifying that theory, but the hype makes it look like a lot more than it is. :)
 
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