Shoji's team pursued an alternate hypothesis. However, the absorption properties of the AA isovaline are opposite to those of the other AAs, meaning that the UV-based explanation alone is either insufficient or incorrect.Īgainst this backdrop, Dr. Scientists verified that this type of radiation can, indeed, induce asymmetric photochemical reactions that, given enough time, would favor the production of L-AAs over D-AAs. One popular explanation for this suggests that the asymmetry was induced by ultraviolet circularly polarized light (CPL) in the star-forming regions of our galaxy. Curiously enough, in the samples obtained from this meteorite, each of the L-enantiomers was more prevalent than its D-enantiomer counterpart. "The idea that homochirality may have originated in space was suggested after AAs were found in the Murchison meteorite that fell in Australia in 1969," explains Dr. As explained in their paper published in The Journal of Physical Chemistry Letters, the team sought to find evidence supporting the cosmic origin of the homochirality of AAs on Earth, as well as iron out some inconsistencies and contradictions in our previous understanding. This phenomenon is known as "chiral symmetry breaking."Īgainst this backdrop, a research team led by Assistant Professor Mitsuo Shoji from University of Tsukuba, Japan, conducted a study aimed at solving this mystery. This suggests that, at some early point in the past, L-AAs must have come to dominate a hetero-chiral world. However, if you synthesize AAs artificially, both L and D forms are produced in equal amounts. It turns out that biological amino acids (AAs)-the building blocks of proteins-on Earth appear only in one of their two possible enantiomeric forms, namely the L-form. Interestingly, one of the many mysteries surrounding the origin of life as we know it has to do with chirality. Even though both versions of a chiral molecule, called "enantiomers," have the same chemical formula, the way they interact with other molecules, especially with other chiral molecules, can vary immensely. Many molecules have a similar property called "chirality," which means that the "left-handed" (L) version of a molecule cannot be superimposed onto its "right-handed" (D) mirror image version. However, no matter how hard you try to flip and rotate one hand, you will never be able to superimpose it perfectly over the other. If you look at your hands, you will notice that they are mirror images of each other.
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