A Clue to the Molecular "Handedness" of Life on Earth

March 17, 2009 / Posted by: Daniella Scalice

Members of NAI’s NASA Goddard Space Flight Center Team have a new paper in PNAS describing the distribution and enantiomeric composition of certain amino acids in carbonaceous meteorites. Their results show an increased amount of “left handed” isovaline in several meteorites, which helps to explain why all known life uses only left-handed versions of amino acids to build proteins.

“Finding more left-handed isovaline in a variety of meteorites supports the theory that amino acids brought to the early Earth by asteroids and comets contributed to the origin of only left-handed based protein life on Earth,” said study co-author Danny Glavin.

The team also found a pattern to the excess. Different types of meteorites had different amounts of water, as determined by the clays and water-bearing minerals found in the meteorites. The team discovered meteorites with more water also had greater amounts of left-handed isovaline.

Mar 17, 2009

Uncle Al said:

There is no credible explanation for biological homochirality: chiral L-protein amino acids and chiral D-sugars. Weak interaction arguments (Mendeleev Commun. 13(3) 129 (2003), Angew. Chem. Int. Ed. 41(24) 4618 (2002)) are woefully insufficient (maximum 8×10^(-12) eV PVED versus ambient kT = 0.0257 eV. An obvious source is a chiral vacuum background in the massed sector (not interactive with EM) consistent with teleparallel gravitation, testable on a lab bench.

Crystallographic space groups P3(1)21 and P3(2)21 are enantiomorphic. All formula units configure into homochiral 3-fold helices (right-handed and left-handed, respectively). There are no conflicting or racemic screw axes. Quartz, berlinite and analogues, tellurium, selenium… single crystals thus furnish atomic-scale left and right “shoes” to test for a vacuum left “foot”. P3(1)21 versus P3(2)21 quartz is particularly good for its commercial production and a control “sock” – amorphous fused silica.

Load an Eotvos balance with macroscopically and chemically indistinguishable single crystal quartz test masses, space group P3(1)21 opposing P3(2)21. 90 days later the net output is either zero (as with all Equivalence Principle tests since Galileo and Stevin in the late 1500s) or non-zero. Observation trumps dialectic. Somebody should look. A non-zero output is followed by each space group run against fused silica. A quartz enantiomorph homochiral to the vacuum background gives a smaller net signal. The two hemiparity experiments’ outputs sum to the full parity experiment’s output as a final validation.