Which Way To Turn?

Given all the bickering going on between Left and Right, it seems apt to mention an item in today’s Science Daily newsletter: a story about new results in the study of biological molecular chirality, something I’ve been curious about for a while.

A brief explanatory preface:

Molecules with identical chemical structure can come in mirror-image forms, the way a light-bulb can have left- or right-handed thread. Things that are identical except for being mirror images of each other are called enantiomorphs, and molecules that pair off in this way are called enantiomers. This property of left- or right-handedness is what is meant by “chirality” (from the Greek cheír, meaning “hand”, as also seen in chiropractor, and chiromancy).

Enantiomers have identical chemical properties, and as a result, when molecules that can take enantiomorphic forms are created in a chemical reaction, they occur in the resulting mixture in equal proportions. (This is referred to as a racemic mixture, or a racemate.)

In living things, however, there are important molecules that only appear as one or the other enantiomer, most notably proteins and sugars. It makes sense that this should be so — life is, after all, dependent upon replication, and upon interacting parts (and it won’t do if the screw doesn’t fit the socket) — but the fact that the chirality of these molecules is common to every living thing on the planet means that the choice was made right at, or even before, the time of life’s origin (or arrival) here on Earth. So the question is: why one enantiomer, and not the other? Was it a purely random choice that, once made, was fixed forever, or was there some compelling and comprehensible reason why things went the way they did?

Well, in today’s article, we learn that a group of French researchers may have something to say about it. Have a look here.

(By the way, if you want to read a truly fascinating book on the subject of mirror-symmetry generally, get yourself a copy of The New Ambidextrous Universe, by the late, great, Martin Gardner.)

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