Why only L amino acids?

John Mack jmack at pipeline.com
Thu Jul 7 22:46:45 EST 1994


In article <9407071344.ZM24336 at model.phr.utexas.edu>,
rhodes at MODEL.PHR.UTEXAS.EDU ("David G. Rhodes") wrote:

> What about coriolis force as an admittedly weak but chiral force???
> 
> }:)
> 
> Seriously, though...
> I seem to recall (~4 years ago) a crystallization/precipitation that
> resulted in a helical structure (Nature paper?).  The authors repeated the
> experiment in a colleague's lab south of the equator, and got the opposite
> chirality.  They could not explain the mechanistic details, as I remember,
> but suggested that coriolis force might be involved.
> 
> ...any ideas???

Yes. We know L-amino acids fold into right-handed helices. (And vice
versa.) 

Therefore, look for forces (coriolis? asymmetric surface catalysts?) that
favor right-handed helices. 

If right-handed helices are favored in one hemisphere due to the coriolis
force, then that may be the hemisphere where these were first incorporated
into successful, Darwinian replicating, nano-machines which eventually
became living things.

Thus, it is just fortuitous that life began in the hemisphere that favored
right-handed helices and also L-amino acids. After all, life would be just
the same with D-amino acids and left-handed helices.

Maybe the L and D nanomachines existed simultaneously on Earth and
dominated their respective hemispheres! But, for some unknown reason (a
comet striking Earth?) the D nanomachines never developed into living
things. The L machines did. The living beings invaded the entire Earth
afterward and chaged conditions such that D nanomachines could not compete
and never became truly alive!



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