Jones brought up the subject of quantum delocalization. What usually comes to mind is the delocalization of electrons since they have a relatively much longer quantum wavelength compared to protons. However delocalization can in principle happen to protons as well (and maybe larger nuclei ?)This paper describes a biological system where delocalization of protons results in 10 000 fold increase in acidity compared to when the particles are treated classically !
Abstract <<Because of the low mass of the proton, nuclear quantum effects can dramatically alter the properties of hydrogen-bond networks, especially when short and strong hydrogen bonds occur. Here, we combine experiments and state-of-the-art simulations that include the quantum nature of both the electrons and nuclei to show that the enzyme ketosteroid isomerase contains a hydrogen-bond network in its active site that facilitates extensive quantum proton delocalization. This leads to a 10,000-fold increase in the acidity of an active-site residue compared with the limit where the nuclei are classical particles. This work opens up new avenues for understanding the interplay between quantum effects and hydrogen bonding in biological systems containing strong hydrogen bonds.>> https://www.pnas.org/content/111/52/18454
