What molecules are we?
L-Alanine1 and L-serine1 are amino acids that are necessary for the biosynthesis of proteins. They are considered “nonessential” in human diets (and those of most other animals) because they are synthesized in the body.
In 1850, long before it was discovered in and isolated from natural substances, alanine was synthesized from acetaldehyde by German chemist Adolph Strecker. Of course, Strecker made the D,L-racemate of the amino acid rather than either isomer alone.
Serine, on the other hand, was first discovered in nature, specifically in silk protein, by German chemist Emil Cramer in 1865. And, speaking of silk . . .
Alanine and serine, along with previous Molecules of the Week glycine and L-proline, are the major amino acids in spider silk proteins. Alanine-rich crystalline areas give silk strength, whereas glycine-rich amorphous regions provide elasticity.
Halloween reminds us of spiders. Spiders spin webs of silk. Silk is made up of proteins. Proteins are polymers of amino acids. Who would have thought that such simple molecules could be scary?
1All amino acids that are biosynthesized into proteins are the L-enantiomers. Some D-enantiomers appear in nature, but they are relatively rare.
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