'Left-handed' amino acid came from meteors

NEW YORK, April 8 (UPI) -- A U.S. researcher has presented evidence that "left-handed" amino acids dominant today came from meteors striking the Earth billions of years ago.

Columbia University Professor Ronald Breslow said the proteins of all forms of life on Earth are composed of amino acids. There are two orientations of amino acids, left and right, that are mirror images of each other. The orientations are called "chirality," and in order for life to arise, proteins must contain only one chiral form of amino acids. With few exceptions, left-handed "L-amino acids" are dominant on Earth.

Breslow said he determined the left-handed form became dominant because amino acids on meteors striking Earth were left-handed. Although meteors start with equal amounts of left- and right-handed amino acids, Breslow said previous experiments showed polarized light from neutron stars the meteors pass selectively destroys one chiral form of amino, resulting in an excess of L-amino acids.

Evidence of left-handed excess has been found on the surfaces of meteorites that have struck Australia and Tennessee within the last 100 years, he added.

Breslow presented his findings this week in New Orleans during the national meeting of the American Chemical Society.