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Re: Alien bacteria and biosphere II
David Levine writes:
> It's not my strong point, but didn't I read somewhere
> once that while a lot of the proteins, etc. we live on,
> while they can be either L- or R- versions (left handed
> or right handed), are all mainly L-? I think I read a
> short story where someone went through a strange experiment
> and came out with an R- based system, and no one knew it.
> He was slowly starving to death because his system couldn't
> use anything he ate. Or am I barking up the wrong tree
> here?
This is actually the case. Certain chemical compounds can have two
isomers, that have the same formula and the same structure when
reflected across a plane of symmetry. Nearly all isomeric compounds
used in biology on Earth are L-isomers. Isomers are chemically
equivalent when reacting with corresponding isomers of the same
handedness, but usually L-isomers and R-isomers are not interchangeable
and an isomer of the wrong handedness is not metabolized. On the other
hand, getting someone reflected in such a way that all their L-isomers
become R-isomers is highly unlikely :-).