Miller/ Urey Experiment

E

Enigma'07

Who turned out the lights?!?!
Registered Senior Member
I have read that Miller used a
mixture that had mostly methane, ammonia, and water
vapor. But then I’ve read that today most scientists
think the early atmosphere had carbon dioxide,
nitrogen, and water vapor because the hydrogen would
have escaped into space. So I’ve heard that if you
replace the Miller/Urey atmosphere with the modern
model you don’t end up with amino acids, but organic
compounds such as formaldehyde and cyanide. So my
question is: I the Miller/Urey experiment truly
accurate? Can formaldehyde and cyanide really give
rise to life?
 
I really cant answer that. But I can tell you that I am performing the experiment in a matter of weeks with the gasses presently on Titan :)

Got the glassware, power supply, and all the rest.... even someone to analyze my product.

Muhahhaha
Later

Proof of what a lot of optimism and determination will accomplish to all of those who said I couldnt do it!!!!!! :p
 
I think methane, ammonia, and water vapor might have existed in the early atmosphere, because cyanide and formaldehyde seems like an unlikely bet to give rise to life; they are poisonous. Hydrogen may have escaped early on, but perhaps before all of it could escape, the gases methane and ammonia may already have existed from reactions in the early earth's hot climate.
 
Facial said:
I think methane, ammonia, and water vapor might have existed in the early atmosphere, because cyanide and formaldehyde seems like an unlikely bet to give rise to life; they are poisonous.
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Poisonous to us, but not necessarily to everything.
 
I think methane, ammonia, and water vapor might have existed in the early atmosphere, because cyanide and formaldehyde seems like an unlikely bet to give rise to life; they are poisonous
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But do you have proof of this, or is it just because the other altenative doesn't seem likely.
 
Well, still the question remains, where did the perbiotic organics come from?
 
Enigma'07 said:
I have read that Miller used a
mixture that had mostly methane, ammonia, and water
vapor. But then I’ve read that today most scientists
think the early atmosphere had carbon dioxide,
nitrogen, and water vapor because the hydrogen would
have escaped into space. So I’ve heard that if you
replace the Miller/Urey atmosphere with the modern
model you don’t end up with amino acids, but organic
compounds such as formaldehyde and cyanide. So my
question is: I the Miller/Urey experiment truly
accurate? Can formaldehyde and cyanide really give
rise to life?
Click to expand...
I don't believe it's exactly known how prebiotic molecules formed on/came to Earth, though you are correct that the Miller and Urey experiment does not accurately model what we believe to be the nature of Earth's early atmosphere. It is still very important, though, since it demonstrates how easily those molecules can be formed from almost wholely inorganic constituents. That's an interesting, though not extremely practical, area of research.
 
I don't have proof, because ammonia is all but nearly nonexistent in the order of abundances of gases in our atmosphere. Formaldehyde and cyanide compounds seem absent as well. Quite puzzling.
 
Enigma'07 said:
I have read that Miller used a
mixture that had mostly methane, ammonia, and water
vapor. But then I’ve read that today most scientists
think the early atmosphere had carbon dioxide,
nitrogen, and water vapor because the hydrogen would
have escaped into space. So I’ve heard that if you
replace the Miller/Urey atmosphere with the modern
model you don’t end up with amino acids, but organic
compounds such as formaldehyde and cyanide. So my
question is: I the Miller/Urey experiment truly
accurate? Can formaldehyde and cyanide really give
rise to life?
Click to expand...
Luckily for us Miller continued on with his experiments.


"But one problem the theory has had to confront was a possible shortage in the primeval oceans of two key pieces in the structure of an RNA molecule, known as cytosine and uracil. Dr. Miller and Dr. Robertson believe they have solved the difficulty.

In companion pieces in the journals Science and Nature, the two scientists report that both substances might have been produced by the lifeless young oceans in ample quantities by a process involving the evaporation of sea water in tropical lagoons, the freezing of sea water in polar regions and the mixing of their products in the open ocean.

The freezing part of the process could have increased sea water concentrations of hydrogen cyanide, Dr. Miller believes. Cyanide is a deadly poison to animals, but it was an essential precursor to many of the molecules from which primitive life arose.

The evaporative part of the process, Dr. Miller said, could have concentrated the traces of urea that accumulate in sea water as a result of reactions in the atmosphere caused by lightning flashes. In experiments, Dr. Miller and Dr. Robertson showed that when the concentration of the simple chemical urea in sea water is high enough, it reacts with another quite common component of sea water that also owes its formation partly to lightning bolts. Under these conditions, the scientists found, the reaction between urea and the second chemical, known as cyanoacetaldehyde, yields fairly large amounts of cytosine, which is one of the nucleotide bases (or "letters") the DNA and RNA molecules use to spell out the genetic "words" controlling protein production and the growth and reproduction of organisms. "

http://www.swcp.com/~diamond/rnabase.html

~Raithere
 
I was just wondering if there is a list of some or all of the proteins that this experiment yeilded. I have been dabbling in the research area on this and am a little curious. I first heard about this experiment from one of my chemistry professors and wasn't fully informed.
 
Docgirl said:
I was just wondering if there is a list of some or all of the proteins that this experiment yeilded.
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There were no proteins formed. What was formed was a "sludge" of various organic molecules (ie. carbon chains and rings) that included, in small quantities, some simple sugars and simple amino acids. Mind you, that's still a very significant result that pre-biotic materials can give rise to organic molecules (even if it turns out that the experimental conditions did not accurately represent Earth's environment at that time).<P>
 
There are many theories as to what the early earth's atmosphere was like, and to my knowledge there is no difinitive proof one way or another. The most important thing you have to realize about this experiement is that It proved that organic compounds could have formed spontaneously, WITHOUT the need of some higher being. the experiment was essential in help prove that evolution from nothing to us is possible.

Btw, I still havent been able to find anyone or a lab to help me finish the experiment. Ill be taking my glassware with me to college though and hopefully a bio or chem prof there will be interested in doing the experiment :)

Later
T
 
Hercules Rockefeller said:
There were no proteins formed. What was formed was a "sludge" of various organic molecules (ie. carbon chains and rings) that included, in small quantities, some simple sugars and simple amino acids. Mind you, that's still a very significant result that pre-biotic materials can give rise to organic molecules (even if it turns out that the experimental conditions did not accurately represent Earth's environment at that time).<P>
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I've read that at least one protein was formed:

Then the German biochemist Klaus Dose and his associates succeeded in showing that one of the products of Fox's experiments was flavin, a naturally-occurring protein.
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http://www.daviddarling.info/encyclopedia/T/thermalprotein.html

Does anyone knows the differences between proteinoids/thermal proteins and proteins? I wonder if it's strictly defined by a minimal number of aminoacids, or maybe structure.... could it be that the only meaningful difference is that proteins are synthesised by living organisms weather proteinoids are not? And if some day someone finds a proteinoid ocurring in an organism, then it would be "promoted" to a protein? As if the definition of proteinoids was a large group of molecules (in a certain pattern), and proteins was an inner group, not essentially different, just like "cars" and "red cars"?
 
Danniel said:
I've read that at least one protein was formed...
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Thanks for that Danniel; I didn’t know that. :) :eek:

OK, after minimal research it appears that “thermal proteins” are thermal polymers (often referred to as ‘polyamino acids’) of three to eight amino acids that can form synthetically (in the sense that they aren’t made by living cells) at high temperatures. It appears that they can only form when glutamic acid is present in excess and that their chemistry is slightly different to “conventional” polypeptides formed by living cells. But I’m no biochemist so I cannot comment further.

It seems that the polyamino acid theory is one theory as to how the first proteins arose on Earth. Just how well supported this theory is, I do not know. But it cannot be at the forefront of mainstream abiogenesis theories as up until now I have never heard of it! (Not that I’m any sort of expert in this area, but I do have a long standing interest.)<P>
 
Enigma'07 said:
Well, still the question remains, where did the perbiotic organics come from?
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Ah, the $64,000 question! RNA will assemble out of free nucleotides if a protein enzyme is present. Howsomever, that protein is large, many kilodaltons, and so won't assemble by itself (and last long enough before degrading). It needs an existing substantial RNA strand to code for this enzyme. This means you need the protein to get the protein. It's like needing a key to unlock a safe when the key's inside it.
 
So basically, something happened back then that can no longer occur in today's world.
 
I'm not willing to go quite that far. I am willing to say that we do not yet understand how it all started.
 
But this proscess isn't going on any more- more life forms arn't randomly developing on our planet.
 
Enigma'07 said:
So basically, something happened back then that can no longer occur in today's world.
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Correct.

There is still much debate is to the composition of the atmosphere when life first arose. There is also much debate is to <I>where</I> life first arose - water on the planet's surface vs hydrothermal vents on the bottom of the ocean vs subterrainean pockets of water deep inside the Earth's crust. But one thing is certain - the Earth was a vastly different place 4 billion years ago (when life first arose) than it is today. With the oxidizing atmosphere of today and the plethora of already-established life, I think the chances of any new life arising <I>de novo</I> are negligable, if not non-existant.<P>
 
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