A second pathway by which life's left handed bias could have formed.

[wattsr1]

Hi All,


Under the title, “Soggy space rocks and left-handed life”, New Scientist (21 March 2009, p 13) reports on an article published by The Proceedings of the National Academy of Science (DOI:10.1073/pnas.0811618106).

Researchers have been studying the amino acid isovaline in six meteorites. What is important about these meteorites is that they show exposure to liquid water varying from 1,000 to 10,000 years, some time in the ancient past. The researchers were able to show that the longer the time that water persisted in the rock, the greater the left handed bias in the molecules of the amino acid.

If this holds up for other amino acids then it is possible that the bias for left handed amino acids, shown by living organisms, may well have been introduced by space rock bombarding the earth.

This constitutes a second pathway by which a left handed bias could have been produced. The first was discovered roughly a decade ago, namely polarized starlight preferentially destroying right handed amino acids.



Regards, Roland

[Roy]

If this holds up for other amino acids then it is possible that the bias for left handed amino acids, shown by living organisms, may well have been introduced by space rock bombarding the earth.

This constitutes a second pathway by which a left handed bias could have been produced. The first was discovered roughly a decade ago, namely polarized starlight preferentially destroying right handed amino acids.

I vaguely recall reading about studies on chirality of amino-acids formed on clay surfaces, which would make this the third pathway..

Roy

[The Pixie]

The first was discovered roughly a decade ago, namely polarized starlight preferentially destroying right handed amino acids.
I have not heard of that. Do you have a link?

[wattsr1]

I have not heard of that. Do you have a link?

Gidday The Pixie,


http://www.americanscientist.org/issues/feature/polarized-starlight-and-the-handedness-of-life

http://www.thefreelibrary.com/Starlight+shows+life+the+right+path-a021015198



Regards, Roland

[wattsr1]

I vaguely recall reading about studies on chirality of amino-acids formed on clay surfaces, which would make this the third pathway..

RoyIndeed.

I put this up on another board too, and received the same reply.


Regards, Roland

[The Pixie]

Roland

Thanks for the links.

I guess talking about the first pathway is not really on topic, but I am going to anyway. I wonder what percentage of the light that falls on an amino acid will have come though one of these polarising nebulae, compared to that which comes from other stars and the sun. My guess would be a very, very small fraction. Is that really going to be enough to tip the balance one way? I cannot see it, unless there is a particular wavelength of light that only appears after passing through the nebula, which I would doubt.

Having said that, looking at the second pathway, this could be the same pathway. Why are the left-handed amino acids becoming dominant? One explanation could be the starlight polarised through nebulae (though I would guess not, for the reason given before).

To anyone: With regards to the clay surface pathway, why would the surface be predominantly left-handed? Are they talking about just a single crystal (which could be handed) producing all the amino acids of the time?

[wattsr1]

Roland

Thanks for the links.

I guess talking about the first pathway is not really on topic, but I am going to anyway. I wonder what percentage of the light that falls on an amino acid will have come though one of these polarising nebulae, compared to that which comes from other stars and the sun. My guess would be a very, very small fraction. Is that really going to be enough to tip the balance one way? I cannot see it, unless there is a particular wavelength of light that only appears after passing through the nebula, which I would doubt.

Having said that, looking at the second pathway, this could be the same pathway. Why are the left-handed amino acids becoming dominant? One explanation could be the starlight polarised through nebulae (though I would guess not, for the reason given before).

To anyone: With regards to the clay surface pathway, why would the surface be predominantly left-handed? Are they talking about just a single crystal (which could be handed) producing all the amino acids of the time?Gidday The Pixie,

I do not know enough to be able to address your questions, except with respect to that second pathway - there they found a direct correlation with respect to the handedness, and the amount of time that the meteorite had been exposed to water some time in the past.:-

"They studied an amino acid called isovaline in six meteorites that showed ancient evidence of 1000 to 10,000 year's exposure to liquid water. The longer the water persisted in the rock, the stronger its left-handed isovaline bias ..."

The article notes that polarization via starlight does not explain the above, and one reason for this is that the starlight bias is not as strong. If starlight gets it started, something else seems to be carrying on with it. In this case, water.

Unfortunately the article is very short and does not say much more.

I guess the question is, will these results hold up the more meteorites and amino acids they study?



Regards, Roland