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Chirality

Chirality in Nature

Whether an object is chiral or not depends on its symmetry.

Tab.1
Some examples of common objects
Achiral objects
Fig.1
Fig.2
Fig.3
Tab.2
Chiral objects
Fig.4
Fig.5
Fig.6
Fig.7

In nature, a huge number of chiral objects are found. For instance, helically formed snails and plants spirally winding round an object are chiral. Not only macroscopic but also microscopic objects like molecules can be chiral. Actually, most molecules, plants, animals, and men are chiral. Usually, only one of the two forms of a chiral molecule can be found in nature. For instance, only one form of each chiral amino acid can be isolated from proteins.

The occurence of only one form of given chiral molecules in nature is the basis of the often totally different biological activity of the two forms of a chiral molecule. Their interaction with other chiral molecules can be compared with gloves; one glove fits, the other does not. The first of the following movies schematically shows the failing attempt of the non-fitting form of a chiral agent to attach to an enzyme. In the second movie, the fitting, mirror-image form of the same chiral agent successfully attaches to the enzyme.

Fig.8
Fig.9
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