Why are we all left handed? – Theory of elementary particle origin
Michael Famiano (Western Michigan University, National Astronomical Observatory ofJapan)
Yirong Mo (Western Michigan University)
Richard Boyd (The Ohio State University)
Toshitaka Kajino (National Astronomical Observatory of Japan, University of Tokyo,Beihang University)
Takashi Onaka (University of Tokyo)
All life is left-handed. You are left-handed; your parents are left-handed. Your pets areleft-handed. Even the blades of grass in your lawn are lefties.
Amino acids are the building blocks of life. They make up the proteins in our bodies.
Because amino acids are asymmetric, then they can have two forms – two mirror images.
Just like your hands, which are mirror images of each other, all amino acids (except forglycine, which is symmetric) have two possible mirror images. One mirror image cannot be
rotated to look like the other. We call these two mirror images “left-handed’’ and“right-handed.” We refer to this handedness as “chirality” from the Latin word for hand.
Except for their chirality, left and right handed amino acids are identical in every otherrespect. Many things in nature are chiral – your hands, snail shells, pine cones, and evensubatomic particles.

Illustration 1: The amino acid alanine in its left-handed form and right-handed form. The
grey, red, blue, and white spheres are carbon, oxygen, nitrogen, and hydrogen respectively.
This bit of knowledge would be mundane were it not for two facts. The first is that allamino acids relevant to life are left-handed. All the amino acids that make up the proteinson our planet come in only one mirror image. Life doesn’t use the right-handed form.
The second fact is that amino acids have been found in meteorites. This means that aminoacids can be made in space. However, not only are amino acids found in meteorites, but theones that have been found are predominantly left-handed. Could it be that amino acids at
not only made in space, but that they are also made with the right chirality?
Since Louis Pasteur studied molecular chirality nearly 170 years ago, chiral molecules havefascinated scientists. Today, how amino acids got to be left-handed is one of the biggest
questions in science with several competing theories. This question is listed by the National
Academy of Sciences and by Science magazine as one of the most important questions inscience today. It has gone unanswered for nearly 120 years.
Now, scientists at Western Michigan University, in collaboration with scientists in
California and Japan, have come up with a possible way in which Mother Nature selects
left-handed amino acids in space. This new theory brings together fundamental particle
physics, electromagnetism, biology, and chemistry. Molecules in magnetic fields caninteract with leptons (some of the tiniest particles in nature which include electrons andneutrinos). Because leptons can also be chiral, they interact with amino acids differently
depending on the combination of lepton chirality and amino acid chirality. This interaction
can selectively destroy one mirror image more than the other, resulting in the imbalancethat we see in meteorites. There are several possible places in the universe where this cantake place.
Not only does this discovery predict how amino acids got to be left-handed, it also predicts
how they became left-handed in space. The ramifications for life on the earth and elsewherein the cosmos are significant.
The latest news on this discovery will be published in Scientific Reports (a Nature journal)
on Monday, June 11 at 10am GMT.
References:
Famiano M.A., Boyd, R.N, Kajino, T., Onaka, T., & Mo, Y., Amino Acid Chiral Selection
Via Weak Interactions in Stellar Environments: Implications for the Origin of Life,
Scientific Reports, vol 8. (2018), www.nature.com/articles/s41598-018-27110-z
Famiano, M.A., Boyd, R.N., Kajino, T., & Onaka, T., Selection of Amino Acid Chirality
via Neutrino Interactions with 14N in Crossed Electric and Magnetic Fields, Astrobiology
18, 190 (1028).
Contact information:Toshitaka Kajino
National Astronomical Observatory of Japan, Division of Theoretical Astronomy
2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Phone: +81 422 34 3740, Fax: +81 422 34 3746
E-mail: kajino@nao.ac.jp