[Gilbert] Levin’s long, strange search for the ultimate sugar replacement started three decades ago, when he stumbled upon chiral chemistry, the well-established principle that complex molecules exist in “right-handed” and “left-handed” forms, known as enantiomers.
There’s an easy way to understand chirality. Hold out your hands, palms facing each other. Imagine that each hand is the chemical structure of a molecule. Most complex molecules are chiral. Like your hands, the two structures of chiral molecules — in sugars, they’re referred to as D and L, from the Latin dexter and laevus — differ only in the arrangement of their elements. Put your hands together and they seem to match exactly. In the same way, the common sugar D-glucose is the mirror image of L-glucose, its rare counterpart. But put your hands down one on top of the other, both facing down, and you’ll see that they’re not identical at all; they’re what chemists call non-superimposable.
Two enantiomers of a molecule will respond identically in a chemical reaction, but not so in biological systems. Proteins and cell receptors are designed to react only with particular enantiomers. For example, the enzymes in your stomach can digest only right-handed sugars. Just as a glove fits only on the proper hand, our bodies distinguish between the enantiomers of any given molecule. [Ratliff]
Ratliff, Evan. “Hitting the Sweet Spot.” Wired. November 2003. <www.wired.com/wired/archive/11.11/newsugar.html> (16 June 2004).
This article appears to be wrong on a number of accounts.
Unless memory fails me, when I learned this in organic, and biochemistry, the dextro and levo forms of the 6 carbon hydrocarbon chain known as glucose, were called isomers (from 2 Greek words) meaning equal parts. Maybe there’s a new terminology, so I’ll give him that point.
The D- form is known as dextrose, the L- form is known as fructose.
Fructose, a.k.a. fruit sugar, is widely recognized as being both sweeter than its counterpart, but also more readily absorbed by the digestive tract, and metabolized by the body.
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