Kulhánek Petr, Schlag Edward W, Koca Jaroslav
National Centre for Biomolecular Research, Faculty of Science, Masaryk University Brno, Kotlárská 2, CZ-611 37 Brno, Czech Republic.
J Am Chem Soc. 2003 Nov 12;125(45):13678-9. doi: 10.1021/ja035800z.
The study presents quantum-chemical calculations on proton transfer in protonated N-acetylglycyl-N1-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.
该研究展示了对质子化的N-乙酰甘氨酰-N1-甲基甘氨酰胺（AGA）作为短寡肽模型中质子转移的量子化学计算。所有计算均采用B3LYP泛函和6-31++G**基组。讨论了两种不同的质子转移机制。第一种机制的速率决定步骤表现出约17.7千卡/摩尔的能垒，其表现为质子围绕羰基双键的异构化。第二种机制基于AGA的大构象灵活性，其中所有羰基氧协同作用。该机制的速率决定步骤表现出仅8.3千卡/摩尔的能垒。
