Chirality; new findings (Introduction)

by David Turell , Thursday, May 15, 2025, 18:37 (7 days ago) @ David Turell

Handedness defines function:

https://www.quantamagazine.org/how-the-universe-differs-from-its-mirror-image-20250514/

"Louis Pasteur discovered while experimenting with some expired wine that certain molecules can be chiral. They can come in distinct left-handed and right-handed structural forms that are impossible to superimpose. Pasteur found that, while they contain all the same components, the mirror versions of chiral molecules can serve distinct chemical functions.

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"Lactose, the sugar found in milk, is chiral. While either version can be synthesized, the sugars produced and consumed by living organisms are always the right-handed ones. In fact, life as we know it uses only right-handed sugars — hence why the genetic staircase of DNA always twists to the right. The root of this “homochirality” remains one of the biggest mysteries clouding the origins of life.

"Worse, if it had contained any bacteria with the opposite handedness, her immune system and antibiotics would have been ill suited to put up a fight. A group of prominent scientists recently cautioned against the synthesis of mirror-image biomolecules(opens a new tab) for this reason — if any were to escape the lab, they could evade every one of life’s defense mechanisms.

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"Nowadays, physicists consider chirality a fundamental property of all elementary particles, just like charge or mass. The particles that don’t have mass are always traveling at the speed of light, and they also all carry an intrinsic angular momentum as though they’re spinning like a top. If the particles are flying in the direction of your thumb, their spin follows the direction your fingers curl — on either your right hand or your left.

"The situation is a bit more complicated for massive particles, such as electrons and quarks. Because a massive particle travels more slowly, a speedy observer could overtake it and effectively reverse its direction of motion, thus flipping its apparent handedness. For this reason, when describing the chirality of massive particles, physicists often refer to the mathematical description of the particle’s quantum properties. When you rotate a particle, its quantum wave function shifts left or right depending on its chirality.

"Almost every elementary particle has a twin through the looking glass. A negatively charged left-handed electron is mirrored by the anti-positron, a negatively charged right-handed particle.

"Similarly, our universe differs from its mirror image. The weak force — the force that’s responsible for radioactive decay — is felt only by left-handed particles. This means that some particles will decay in the normal world while their counterparts in the mirror would not.

"Plus, there’s one particle that seems not to show up in the mirror at all. The neutrino has only ever been observed in its left-handed form. Particle physicists are investigating whether the right-handed neutrino exists or if neutrinos’ mirror images are simply identical, which could help explain why the universe contains something rather than nothing."

Comment: chirality seems to be the key to everything. That specificity seems designed. Since both handedness types are naturally available why does biochemistry make such choices?

Not answered