Amino Acids and Rotation of Light.

From: John Couch (
Date: Fri Jun 21 2002 - 13:26:02 PDT

Dear Snacktalk,
"All of the proteins in your body and in all organisms on earth are made
from amino acids that rotate the direction of polarization of light to the
left." This is an error. These amino acids all share the L configuration but
not the same optical direction of rotation. Sue the chemists over this
confusing nomenclature.

Although the natural amino acids are all L types, they do not all rotate
light in the same direction. The L refers to their relationship to
glyceraldehyde and not to the direction of rotation of light of the amino
acid itself. Some L acids rotate one way and some the other.

If you do an experiment with amino acids try alanine, leucine, methionine,
tryptophan, tyrosine, etc. The ring and sulfur acids tend to rotate
differently to the others.

John Couch

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