What molecules are we?
L-Alanine1 and L-serine1 are amino acids that are necessary for the biosynthesis of proteins. They are considered 鈥渘onessential鈥� 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 . 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.
L-Alanine hazard information
| GHS classification*: not a hazardous substance or mixture听 |
*Globally Harmonized System of Classification and Labeling of Chemicals.听
L-Serine hazard information
| GHS classification: not a hazardous substance or mixture听 |
MOTW update:听October 29, 2018
Skatole was the Molecule of the Week for March 5, 2012. It鈥檚 what causes mammalian feces to smell bad. Recently, scientists in China, Singapore, and the United States reported the discovery of the enzyme, indoleacetate decarboxylase, which bacteria use to 听in the gut.
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L-Alanine fast facts
| CAS Reg. No. | 56-41-7 |
| Empirical formula | C3H7NO2 |
| Molar mass | 89.09 g/mol |
| Appearance | White crystals or powder |
| Melting point | 鈮�300 潞C (dec.) |
| Water solubility | 167 g/L |
L-Serine fast facts
| CAS Reg. No. | 56-45-1 |
| Empirical formula | C3H7NO3 |
| Molar mass | 105.09 g/mol |
| Appearance | White crystals or powder |
| Melting point | 220鈥�250 潞C (dec.) |
| Water solubility | 425 g/L |
MOTW update: November 5, 2018
L-Alanine and L-Serine were the Molecules of the Week for October 29, 2018. They, along with glycine听and L-proline, are the chief amino acids that make up spider silk proteins. In the past month, chemists at San Diego State University and Northwestern University (Evanston, IL) discovered that before spiders spin their silk, they .
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