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Chiral Skin Care

By: Shyam Gupta, PhD, and Linda Walker
Posted: November 5, 2010, from the November 2010 issue of GCI Magazine.
Chiral Skin Care

The left-handed and right-handed molecules usually have different physical, chemical and biological properties.

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All organic materials are either achiral or chiral, and an organic material can contain more than one chiral carbon atom. However, note that these organic materials can also be synthetic—and they, too, are thus either achiral or chiral (see Nature Identical).

Mother Nature is a Chemist

Molecules produced in nature are mostly chiral, and chiral molecules play a critical role in the biology of all living matter. Mother Nature is also three-dimensional and left-handed.

Again, when an organic compound contains at least one carbon atom (asymmetric carbon) to which those four atoms attached are different in chemical nature, then that molecule is chiral, and these molecules are left-handed or right-handed—depending on the orientation of those four atoms attached to the asymmetric carbon.

Among popular methods of nomenclature, chiral molecules are designated D or L; chiral atoms are labeled R or S. Chiral molecules have a unique physical property of deflecting a beam of polarized light to either the left or the right side of a centerline. However, a left-handed molecule, for example, may deflect polarized light to either the left or the right side of that centerline. The direction of that rotation is not directly related to either left- or right-handedness of a chiral molecule. The direction of light deflection is designated (+) for right-handed (d) and (-) for left-handed (l) rotation. The left-handed and right-handed molecules usually have different physical, chemical and biological properties, and the pharmaceuticals industry has utilized this variance in biological properties of chiral ingredients, both natural and synthetic, in the treatment of human ailments for a long time. Amoxicillin, a commonly prescribed penicillin derivative, is a good example of a chiral molecule and the importance of the orientation of its carbon molecules has the chemical name: (2S,5R,6R)-6-[(R)-(-)-2-amino-2-(p-hydroxyphenyl) acetamido]-3, 3- dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0] heptane-2-carboxylic acid. Note the chiral molecules labeled with “S” and “R.” In this case, the change of orientation of any of the carbons labeled as such usually leads to the total loss of the biological activity.

Chirality All Around You—Consider the Applications

Chiral molecules exist everywhere. Your own DNA is chiral—as are your hormones, enzymes and the structural components of tissue, blood, hair and skin. Consider, too, the building blocks of proteins—amino acids. They are thought to be the first organic molecules produced on Earth via abiogenesis (the primordial soup theory), and all amino acids are chiral, with the exception glycine.