A Novel Mechanism of Proton Transfer in Protonated Peptides

The study presents quantum-chemical calculations on proton transfer in protonated N-acetylglycyl-N -methylglycinamide (AGA) as a short oligopeptide model. All calculations employ the B3LYP functional and the 6-31++G** basis set. Two different mechanisms of proton transfer are discussed. The rate-det...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2003-11, Vol.125 (45), p.13678-13679
Main Authors: Kulhánek, Petr, Schlag, Edward W, Koča, Jaroslav
Format: Article
Language:English
Subjects:
Atomic and molecular physics
Bond strengths, dissociation energies
Exact sciences and technology
Glycine - analogs & derivatives
Glycine - chemistry
Molecular properties and interactions with photons
Peptides - chemistry
Physics
Properties of molecules and molecular ions
Protein Conformation
Protons
Thermodynamics
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Summary:The study presents quantum-chemical calculations on proton transfer in protonated N-acetylglycyl-N -methylglycinamide (AGA) as a short oligopeptide model. All calculations employ the B3LYP functional and the 6-31++G** basis set. Two different mechanisms of proton transfer are discussed. The rate-determining step of the first mechanism exhibits an energy barrier of about 17.7 kcal mol-1, and it is represented by an isomerization of the proton around the double bond of the carbonyl group. The second mechanism is based on the large conformational flexibility of AGA, where all carbonyl oxygens cooperate. The rate-determining step of this mechanism exhibits an energy barrier of only 8.3 kcal mol-1.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja035800z