A new study has found that molecules, like us, can be destined to be strictly left or right-handed. Just like placing our hands together to mirror each other, molecules have the same characteristics and can be the “opposite” of other molecules.
This is known as “chirality.” You can get a good idea of what chirality is by putting a right-handed glove on your left hand: two identical shapes that cannot be superimposed because they are mirror images of each other. The way these molecules are found to be either left or right-handed is by studying the direction in which they emit electrons.
The study of chirality in molecules
In the study performed by Institut National de la Recherche Scientifique (INRS), scientists studied the molecules’ photoionization, which describes the way they emit electrons when hit by light.
Light produced by an ultraviolet laser in the lab was circularly polarized and then directed at camphor molecules. When exposed to the light, a spiral pattern formed in the electromagnetic field. Once this light pattern hit the molecules, it emitted an electron that followed its own spiral path.
Gaseous camphor molecules are oriented in a random fashion, so the laser beam doesn’t always hit the chiral molecule on the same side, and electrons are emitted in different directions. Yet for a given mirror image, more electrons are emitted either in the same or opposite direction as the light, depending on the direction of the polarization, just like a nut turns one way or another depending on which direction the wrench is turned.
Samuel Beaulieu, a PhD student in energy and materials co-supervised at lNRS and the University of Bordeaux, and his team studied how electrons were emitted once the light hit the molecules. They found that not only were more electrons emitted when they traveled in a certain direction, but that they also traveled a few attoseconds earlier than if they had traveled in the opposite direction. This means the reaction of a camphor molecule ionized by circularly polarized light is asymmetric.
This asymmetric characterization could be one explanation for the homochiral (left or right-handed) nature of living organisms. Samuel Beaulieu’s experiment captured the first few attoseconds of a process that over billions of year of evolution could have led to a preference for certain left-handed or right-handed molecules in the chemistry of life.