Over the course of the semester, our trainees are reviewing webinars in their given fields and preparing abstracts to help colleagues outside their discipline make an informed choice about watching them. As our program bridges diverse disciplines, these abstracts are beneficial for our own group in helping one another gain key knowledge in each other’s fields. We are happy to share these here for anyone else who may find them helpful.
An evolutionary mystery: Mirror asymmetry in life and space
Brett McGuire, National Radio astronomy observatory
July 17, 2020
American Chemical Society webinars
Watch the video on the ACS website >>
Have you ever wondered why living organisms preferentially selected L-amino acids (Left-handed) as major building blocks instead of the D-amino acids (right-handed)? In this webinar, Dr. Brett McGuire discusses the possibility of using astrochemistry to study the occurrence of homochirality of molecules of life.
Astrochemistry is the study of molecules in space. He gave a brief overview of chemical delivery into interstellar space which is believed to have occurred when meteorites bombarded new stars and planets formed from a stellar nursery. He highlighted how life may have emanated from complex organic molecules delivered on earth through this process and the question of which point in these astronomical processes chiral selection occurred, thus how and when did homochirality arrive.
Was it by chance, was the synthesis of these biomolecules catalyzed by a chiral mineral, or did it occur out of space? To evaluate the possibility of chiral selection occurring in space, samples of meteorites from Australia were analyzed. They observed a 10% excess in a few of the amino acids found in the meteorites, which does not fully explain that homochirality occurred in space but at least is a possible indication since none of the D-amino acids were in excess.
Dr. McGuire discussed various physical phenomena that may have led to an L-amino acid enantiomeric excess. Selective destruction of molecules by polarized electrons that are generated by beta decay can lead to enantiomeric excess, but this phenomenon should lead to a similar distribution of enantiomers in stellar spaces. However, using circular-polarized UV radiation they observed changes in the distribution of amino acid enantiomers at different stellar regions and it is more dependent on the radioactive environment.
He also highlighted how they tried to measure the enantiomeric excess of propylene oxide from their rational energy transition in the Sagittarius B2N interstellar space. Although they could detect propylene oxide in the Sagittarius B2N their approach could not differentiate between L and D propylene oxide. Further research is being conducted to optimize a circular dichroism method that can measure enantiomeric excess of propylene oxide.
This webinar is an eye-opener to unveiling where homochirality may evolve from.