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Author Topic:   The Recurrent Problem of Chirality
Member (Idle past 6327 days)
Posts: 126
From: Cymru
Joined: 02-13-2006

Message 16 of 81 (320937)
06-12-2006 8:03 PM
Reply to: Message 1 by Evopeach
02-09-2006 4:49 PM

I know this is an old post but thought I'd stick this here.
A recent paper showed how cosmic radiation could cause a bias towards L-amino acids in space (I could find the ref if required). Last week another study (Klusserman et al. 2006, Nature 441) indicated that whether the original compostion of amino acids be 100:1 levo/dextro or 100:99 levo/dextro - the resulting solution will be predominately levo. So would not a cosmic source of amino acids with a slight bias towards levo become overwhelmingly levo when deposited on dissolved on the earth?

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Replies to this message:
 Message 17 by Coragyps, posted 06-12-2006 8:41 PM melatonin has replied

Member (Idle past 6327 days)
Posts: 126
From: Cymru
Joined: 02-13-2006

Message 18 of 81 (320950)
06-12-2006 8:53 PM
Reply to: Message 17 by Coragyps
06-12-2006 8:41 PM

Right-handed amino acids were left behind
02 June 2006 news service
A CLUE to the mystery of how nature selected left-handed amino acids rather right-handed ones may lie in the way the substances behave as they dissolve in water.
Amino acids can appear in left-handed (L) and right-handed (D) mirror-image forms. When made from scratch in the lab the two versions are equally likely to appear, but in nature, L amino acids dominate.
Donna Blackmond at Imperial College London and colleagues dissolved a mixture of solid L and D versions of the amino acid serine in water. They found that a small difference in the initial proportion of one version gets amplified in the resulting solution. So a 100:1 mixture of L- and D-serine produces a solution made up almost entirely of L-serine, but so does a 100:99 mixture (Nature, vol 441, p 621).
"It doesn't matter what proportions of solid amino acids you throw in, you always get exactly the same proportions in solution," says Blackmond, whose team has found a similar effect with other amino acids. She says she is surprised that no one noticed the effect before.
This effect could have amplified a slight excess of L-amino acids in nature. Why there was a slight excess to start with is another question.
Here's a YSI link of the Klasserman et al. 2006 article (pdf format)...

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