Biophysical aspects of intra-protein proton transfer

The passage of proton trough proteins is common to all membranal energy conserving enzymes. While the routes differ among the various proteins, the mechanism of proton propagation is based on the same chemical-physical principles. The proton progresses through a sequence of dissociation association steps where the protein and water molecules function as a solvent that lowers the energy penalty associated with the generation of ions in the protein. The propagation of the proton in the protein is a random walk, between the temporary proton binding sites that make the conducting path, that is biased by the intra-protein electrostatic potential. Kinetic measurements of proton transfer reactions, in the sub-ns up to micros time frame, allow to monitor the dynamics of the partial reactions of an overall proton transfer through a protein.