It’s long been a mystery why cells use one hand of two-handed molecules, like left-handed amino acids and right-handed sugars. A new proposal solves the mystery, explaining how this phenomenon called homochirality arises naturally. Wait a minute…
“Life scientists unlock mystery of how ‘handedness’ arises,” announced a headline on PhysOrg. Dr. Thomas G. Mason, a professor of chemistry and physics at UCLA, was fascinated by the long-standing mystery of how life chooses one hand over the other when either “isoform” is equally probable. “Why many of the important functional molecules in our bodies almost always occur in just one chiral form when they could potentially exist in either is a mystery that has confounded researchers for years,” the article said.
So what is his solution? Surprisingly, it’s entropy – something we usually associate with disorder and randomness.
“It’s quite bizarre,” Mason said. “You’re starting with achiral components — triangles — which undergo Brownian motion and you end up with the spontaneous formation of super-structures that have a handedness or chirality. I would never have anticipated that in a million years.”
.…“We discovered that just two physical ingredients — entropy and particle shape — are enough to cause chirality to appear spontaneously in dense systems,” Mason said. “In my 25 years of doing research, I never thought that I would see chirality occur in a system of achiral objects driven by entropic forces.”
The body of the article explains, though, that he didn’t try his experiment with actual amino acids or biological molecules. He experimented with colored equilateral triangles, imprinting them on a static surface using lithography. He perceived “superstructures” made up of parallelograms in the densely-packed arrangement.
Does this have anything to do with life? Not yet. “We’re learning some new physical rules, but the story in biology is far from complete. We have added another chapter to the story, and I’m amazed by these findings,” he said….
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