Live, left or right, for something?

2014/09/30 Carton Virto, Eider - Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Fisika
• Biologia

One of the questions about the evolution of life is why biological molecules are left or right. Many molecules are chiral, that is, like the hands, have left and right versions, which are mirror images, but not equal. And life has shown “priority”, as the case may be, regarding a version and not of molecules. The DNA molecule, for example, is right. It could be to the left, but it is not, and the same happens with other biomolecules: most amino acids are to the left, while sugars are to the right (polarized light deviates in one direction or another, according to which molecules are classified to the left or right).

If behind this hand preference there is a physical reason, or if it happened randomly, it remains an unanswered question. It may happen that, at the time of life, there has been an imbalance by pure chance between the left and right versions of the organic molecules of the soup, and subsequently, over time, the initially small difference will be amplified. According to this hypothesis, there would be no concrete physical reason to explain why the left or the right are biological molecules.

Other hypotheses argue that there are physical phenomena that can produce an imbalance in the number of left and right molecules, and that they were probably responsible for the asymmetry of the original soup. One of these possible agents are the left electrons, hypotheses that some physicists of the University of Nebraska have demonstrated. The experiment, which has 13 years of research, has just been published in the journal Physical Review Letters.

The experiment used the left/right electrons and the bromokanfor-left/right molecule (an organic molecule used as a sedative). In each case, the slow left or right electrons have been thrown against gaseous left or right molecules. Electrons have destroyed molecules, and the results have shown that right electrons destroy more right molecules and the more left electrons. The difference is very small, 0.03%, but systematic, and researchers have stressed that the design of the experiment has avoided other possible mechanisms of molecular destruction. This has been one of the problems of other experiments that have so far been carried out to test this type of hypothesis. That selective destruction was related to electron polarity.

Cosmic rays

Left-handed electrons originate from the beta disintegration of radioactive nuclei and the influence of cosmic rays in the atmosphere (in this case, the relationship between the electron spin and the direction of motion defines whether it is left or right). F. 1962 Vester, T. L. Ulbricht and H. Researchers Krauch proposed that these leftists could be the cause of asymmetry in that prebiotic soup, which in the case of DNA was pioneering destroying more left.

The results of the physics experiment at the University of Nebraska do not demonstrate the hypothesis of Vester-Ulbricht, and so have their authors. They have considered it as a first step and the next is to test what happens to biological molecules. It is basically a basic science experiment to find an answer to a basic question.