Proton tunneling is a type of quantum tunneling involving the instantaneous disappearance of a proton in one site and the appearance of the same proton at an adjacent site separated by a potential barrier. The two available sites are bounded by a double well potential of which its shape, width and height are determined by a set of boundary conditions. According to the WKB approximation, the probability for a particle to tunnel is inversely proportional to its mass and the width of the potential barrier. Electron tunneling is well-known. A proton is about 2000 times more massive than an electron, so it has a much lower probability of tunneling; nevertheless, proton tunneling still occurs especially at low temperatures and high pressures where the width of the potential barrier is decreased.
Proton tunneling is usually associated with hydrogen bonds. In many molecules that contain hydrogen, the hydrogen atoms are linked to two non-hydrogen atoms via a hydrogen bond at one end and a covalent bond at the other. A hydrogen atom without its electron is reduced to being a proton. Since the electron is no longer bound to the hydrogen atom in a hydrogen bond, this is equivalent to a proton resting in one of the wells of a double well potential as described above. When proton tunneling occurs, the hydrogen bond and covalent bonds are switched. Once proton tunneling occurs, the same proton has the same probability of tunneling back to its original site provided the double well potential is symmetrical.
The base pairs of a DNA strand are connected by hydrogen bonds. In essence, the genetic code is contained by a unique arrangement of hydrogen bonds. It is believed that upon the replication of a DNA strand there is a probability for proton tunneling to occur which changes the hydrogen bond configuration; this leads to a slight alteration of the hereditary code which is the basis of mutations.[1] Likewise, proton tunneling is also believed to be responsible for the occurrence of the dysfunction of cells (tumors and cancer) and ageing.
Proton tunneling occurs in many hydrogen based molecular crystals such as ice. It is believed that the phase transition between the hexagonal (ice Ih) and orthorhombic (ice XI) phases of ice is enabled by proton tunneling.[2] The occurrence of correlated proton tunneling in clusters of ice has also been reported recently.[3][4][5]
^Löwdin, P. O. (1963). "Proton Tunneling in DNA and its Biological Implications". Rev. Mod. Phys. 35 (3): 724–732. Bibcode:1963RvMP...35..724L. doi:10.1103/RevModPhys.35.724.
^Castro Neto, A. H.; Pujol, P.; Fradkin, E. (2006). "Ice: A strongly correlated proton system". Phys. Rev. B. 74 (2): 024302. arXiv:cond-mat/0511092. Bibcode:2006PhRvB..74b4302C. doi:10.1103/PhysRevB.74.024302. S2CID 102581583.
^Drechsel-Grau, C.; Marx, D. (2014). "Quantum Simulation of Collective Proton Tunneling in Hexagonal Ice Crystals". Phys. Rev. Lett. 112 (14): 148302. Bibcode:2014PhRvL.112n8302D. doi:10.1103/PhysRevLett.112.148302. PMID 24766024.
^Yen, F.; Gao, T. (2015). "Dielectric Anomaly in Ice near 20 K: Evidence of Macroscopic Quantum Phenomena". J. Phys. Chem. Lett. 6 (14): 2822–2825. arXiv:1508.00215. doi:10.1021/acs.jpclett.5b00797. PMID 26266868. S2CID 38375110.
^Meng, X. Z.; et al. (2015). "Direct visualization of concerted proton tunnelling in a water nanocluster". Nat. Phys. 11 (3): 235–239. Bibcode:2015NatPh..11..235M. doi:10.1038/NPHYS3225.
November 27, 2023
proton, tunneling, type, quantum, tunneling, involving, instantaneous, disappearance, proton, site, appearance, same, proton, adjacent, site, separated, potential, barrier, available, sites, bounded, double, well, potential, which, shape, width, height, determ. Proton tunneling is a type of quantum tunneling involving the instantaneous disappearance of a proton in one site and the appearance of the same proton at an adjacent site separated by a potential barrier The two available sites are bounded by a double well potential of which its shape width and height are determined by a set of boundary conditions According to the WKB approximation the probability for a particle to tunnel is inversely proportional to its mass and the width of the potential barrier Electron tunneling is well known A proton is about 2000 times more massive than an electron so it has a much lower probability of tunneling nevertheless proton tunneling still occurs especially at low temperatures and high pressures where the width of the potential barrier is decreased Proton tunneling is usually associated with hydrogen bonds In many molecules that contain hydrogen the hydrogen atoms are linked to two non hydrogen atoms via a hydrogen bond at one end and a covalent bond at the other A hydrogen atom without its electron is reduced to being a proton Since the electron is no longer bound to the hydrogen atom in a hydrogen bond this is equivalent to a proton resting in one of the wells of a double well potential as described above When proton tunneling occurs the hydrogen bond and covalent bonds are switched Once proton tunneling occurs the same proton has the same probability of tunneling back to its original site provided the double well potential is symmetrical The base pairs of a DNA strand are connected by hydrogen bonds In essence the genetic code is contained by a unique arrangement of hydrogen bonds It is believed that upon the replication of a DNA strand there is a probability for proton tunneling to occur which changes the hydrogen bond configuration this leads to a slight alteration of the hereditary code which is the basis of mutations 1 Likewise proton tunneling is also believed to be responsible for the occurrence of the dysfunction of cells tumors and cancer and ageing Proton tunneling occurs in many hydrogen based molecular crystals such as ice It is believed that the phase transition between the hexagonal ice Ih and orthorhombic ice XI phases of ice is enabled by proton tunneling 2 The occurrence of correlated proton tunneling in clusters of ice has also been reported recently 3 4 5 See also editQuantum tunneling Hydrogen bondReferences edit Lowdin P O 1963 Proton Tunneling in DNA and its Biological Implications Rev Mod Phys 35 3 724 732 Bibcode 1963RvMP 35 724L doi 10 1103 RevModPhys 35 724 Castro Neto A H Pujol P Fradkin E 2006 Ice A strongly correlated proton system Phys Rev B 74 2 024302 arXiv cond mat 0511092 Bibcode 2006PhRvB 74b4302C doi 10 1103 PhysRevB 74 024302 S2CID 102581583 Drechsel Grau C Marx D 2014 Quantum Simulation of Collective Proton Tunneling in Hexagonal Ice Crystals Phys Rev Lett 112 14 148302 Bibcode 2014PhRvL 112n8302D doi 10 1103 PhysRevLett 112 148302 PMID 24766024 Yen F Gao T 2015 Dielectric Anomaly in Ice near 20 K Evidence of Macroscopic Quantum Phenomena J Phys Chem Lett 6 14 2822 2825 arXiv 1508 00215 doi 10 1021 acs jpclett 5b00797 PMID 26266868 S2CID 38375110 Meng X Z et al 2015 Direct visualization of concerted proton tunnelling in a water nanocluster Nat Phys 11 3 235 239 Bibcode 2015NatPh 11 235M doi 10 1038 NPHYS3225 Retrieved from https en wikipedia org w index php title Proton tunneling amp oldid 1146755889, wikipedia, wiki, book, books, library,
