Barrierless proton transfer within short protonated peptides in the presence of water bridges. A density functional theory study.
We have used density functional theory at the B3LYP/6-31++G(d,p) level of theory to investigate proton transfer in protonated N(2)-acetyl-N(1)-methylglycinamide and N-acetylglycyl-N(1)-methylglycinamide with multiwater assistance and to determine the structures and energies of the most important minima and transition states corresponding to the proton-transfer pathways. We propose mechanisms for proton transfer between adjacent and nonadjacent carbonyl oxygen atoms with water bridge assistance. The presence of a two-water bridge connected to the two carbonyl oxygen atoms provides a proton-transfer mechanism having such a low-barrier that the excess proton is almost freely mobile.
Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan.
Po-Tuan
PT
Chen
Chia-Ching
CC
Wang
Jyh-Chiang
JC
Jiang
Hsi-Kai
HK
Wang
Michitoshi
M
Hayashi
D005998:Glycine / Q000031:analogs & derivatives / Q000737:chemistry; D008962:Models, Theoretical; D010100:Oxygen / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
C480766:N-acetylglycyl-N'-methylglycinamide; D010455:Peptides; D011522:Protons; D014867:Water; D010100:Oxygen; D005998:Glycine