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To: GodGunsGuts

Here’s an interesting bit of fairly recent information on the chirality problem. It seems that nature can and does sometimes produce amazingly lopsided chiralities:

Direct asymmetric intermolecular aldol reactions catalyzed by amino acids and small peptides.Córdova A, Zou W, Dziedzic P, Ibrahem I, Reyes E, Xu Y.
Department of Organic Chemistry, The Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden. acordova@organ.su.se

In nature there are at least nineteen different acyclic amino acids that act as the building blocks of polypeptides and proteins with different functions. Here we report that alpha-amino acids, beta-amino acids, and chiral amines containing primary amine functions catalyze direct asymmetric intermolecular aldol reactions with high enantioselectivities. Moreover, the amino acids can be combined into highly modular natural and unusual small peptides that also catalyze direct asymmetric intermolecular aldol reactions with high stereoselectivities, to furnish the corresponding aldol products with up to >99 % ee. Simple amino acids and small peptides can thus catalyze asymmetric aldol reactions with stereoselectivities matching those of natural enzymes that have evolved over billions of years. A small amount of water accelerates the asymmetric aldol reactions catalyzed by amino acids and small peptides, and also increases their stereoselectivities. Notably, small peptides and amino acid tetrazoles were able to catalyze direct asymmetric aldol reactions with high enantioselectivities in water, while the parent amino acids, in stark contrast, furnished nearly racemic products. These results suggest that the prebiotic oligomerization of amino acids to peptides may plausibly have been a link in the evolution of the homochirality of sugars. The mechanism and stereochemistry of the reactions are also discussed.
http://www.ncbi.nlm.nih.gov/pubmed/16637082?dopt=AbstractPlus

Again, the author is in over his head claiming things are “not possible”.


138 posted on 01/12/2009 12:04:38 PM PST by cacoethes_resipisco
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To: cacoethes_resipisco

Please be specific. What “things” in relation to homochirality are you claiming that the author says is impossible? A direct quote would be nice.


141 posted on 01/12/2009 12:10:17 PM PST by GodGunsGuts
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To: GodGunsGuts
...with stereoselectivities matching those of natural enzymes that have evolved over billions of years.

That killed it for me right there.But then to turn around and say someone else is over their head is downright comical!

(Say GGG, whoever the original poster was, 'cacoethes_resipiscom' no longer exists?Because I can't reply!)

264 posted on 01/12/2009 3:14:12 PM PST by tpanther (The only thing necessary for the triumph of evil is for good men to do nothing---Edmund Burke)
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