Found some more interesting articles
Talks about measuring the age of organic matter by the ratio of D and L amino acids (over time molecules convert L to D and D to L and end up in equilibrium ...)
The Rockefeller University » testpost for LDAP authorlogin
Talks about a Potassium filter that needs D and L amino acids but uses glycerin as an ambidextrous one instead: "Glycine’s being the only natural amino acid that can play this role helps explain why the potassium ion filters of all organisms are identical."
the google "clip" on this site is intriguing, but requires AAAS sign in to access the article (abstract doesn't mention it)Just a moment...
"But many bacteria and fungi can turn to an alternative system that allows ... it a specific left- or right-handed amino acid or some other compound--to a ..."
and I love these little guysMagnetotactic bacteria - Wikipedia
biological compass bacteria?
Novel neurotransmitter overturns laws of biology, offers potential for stroke treatment
The neurotransmitter is an amino acid called D-serine. It's odd, Snyder says, because it differs in structure from any known molecule in its class found in mammals and other higher animals. D-serine is what chemists call a right handed amino acid. Normally, amino acids have atoms that extend from the left side of the molecule. These L-amino acids, as they're called, are the rule in vertebrates, whose biochemistry is set up to deal with these forms.
Some primitive organisms, however, notably bacteria, have a mixture of both L-amino acids and their mirror images called D-amino acids. But to find a D-amino acid in humans, Snyder says, "is unprecedented;" it's the equivalent of finding a Pterodactyl in your local pet shop.
Moreover, unlike dopamine, serotonin or other traditional nerve transmitters, D-serine isn't secreted at nerve cell endings in the brain. Instead, it comes from adjacent cells called astrocytes, which enclose nerve cells in the brain's gray matter like a glove.
The current study adds conclusive evidence to the idea that D-serine -- released from astrocytes -- activates receptors on key nerve cells in the brain. Activating these receptors, called NMDA receptors, has long been linked with learning, memory and higher thought. NMDA receptors are also known culprits in stroke damage in the brain, and have become a focus for anti-stroke research.
So they do exist, and D-amino acids are used (a) by some bacteria and (b) (at least one anyway) by humans.
we are limited in our ability to understand
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