Let's Make This Post go Chiral: From Amino Acids to Zwitterions

      A recent RadioLab story inspired this week's post on chirality; we certainly hope this Partial Ellipsis of the Sun post goes chiral! 

      Chirality is the property of having a structure that is non-superimposable on its mirror image. The term chirality is derived from the Greek word for hand, χειρ (kheir).

      The mirror images of a chiral molecule/ion are called enantiomers or optical isomers.

     Most DNA (B-DNA) double-helix molecules are right-handed, though there are some DNA molecules called Z-DNA that are left-handed. Thus, the labels on the following diagram are correct for most DNA.

     The chirality of molecules has much importance in biomolecules and in pharmaceuticals where left-handed molecules are more often the norm; the toxic version in right-handed molecules (like thalidomide) are the abnormal and destructive ones. Ironic that the handedness of molecules caused so much hand/arm (and foot/leg) deformities in thalidomide babies.

      On earth, amino acids characteristic of life are all left-handed in shape (Levo), and cannot be exchanged for their right-handed (Dextro) counterparts.  However, all sugars characteristic of life on Earth are right-handed, hence, dextrose. The opposite hands for both amino acids and sugars exist in the universe, but they just aren’t utilized by any known biological life form.

      A zwitterion is a neutral molecule with both positive and negative electrical charges. The image on the right (above) is a zwitterion.

     Thus, amino acids in earth's life forms go left, sugars go right, DNA double helixes go right. What's the Chirality Winner? ;-)

Please hand in your Chiral thoughts. . .
Steph

(And here's Telluride, CO, this weekend to clear your head and hands from all those chiral molecules):

Kangaroos are Southpaws in More Ways Than One

     Kangaroos are predominantly left-pawed according to a June 18, 2015, study of Eastern Gray and Red kangaroos published in Cell Biology by Andrey Giljov et al of Saint Petersburg State University. 

     The pawedness of these bipedal marsupials was observed during eating and grooming. A connection to walking on two legs for a paw dominance was noted. Bipedal wallabies (shown below) also showed a left-hand preference. The wallabies used their left paws for fine motor skills and right paws for strength. Quadruped marsupials like tree kangaroos did not show a predominant paw.

      The researchers were surprised to find a dominant paw at all since marsupial brains do not have a corpus callosum, the connecting tissue between the two sides of the brain which humans and many other placental mammals have.

      This Smithsonian article describes the kangaroo research as being useful to understanding dominant handedness in humans. Additionally, left-handedness in humans correlates with less specialized brains.

      Any southpaws out there among PEOTSers? Maizie is right-pawed and I am right-handed.

Chirality yours,
Steph