羟自由基与Neu5Gc抽氢反应的理论动力学研究

Theoretical and Kinetic Study of the Hydrogen Atom Abstraction Reactions of Neu5Gc with Hydroxyl Radical

红肉风险物质N-羟乙酰神经氨酸(Neu5Gc)可诱发炎症,但与食品消费代谢和加工贮藏过程相关的羟自由基(OH·)互作机制未知。体外OH·模拟试验表明过氧化氢(H2O2)添加量2%,254 nm紫外灯15处理60 min时对Neu5Gc标准品含量降低效果最佳为76.23%±2.17%。为探究该过程机制,首先在气相、水和苯相下以M062X/6-31+G(d,p)理论水平对OH·作用Neu5Gc分子中羟基氢和非羟基氢抽提反应的各驻点进行优化和焓值校正,M062X/def2TZVP水平计算能垒。其次,298 K^453 K内以过渡态理论和三参数阿伦尼乌斯方程分别获得反应速率和动力学参数。结果表明:气相和苯相下Neu5Gc中H24位抽氢能垒最低,分别为13.20 kJ/mol和19.54 kJ/mol;水相下H 29位能垒最低6.25 kJ/mol;气相下活化能最低为H 39位8.09 kJ/mol,苯相下最低为H 38位1.72 kJ/mol,水相最低为H 24位14.3 kJ/mol;273到453 K间,Neu5Gc分子中非羟基氢处抽氢速率最大可高于羟基氢108倍。综上,OH·主要通过对Neu5Gc非羟基氢原子的氢抽提反应进行相互作用。

The new red meat and it’s products risk factor N-glycolylneuraminic acid(Neu5Gc)can induced inflammation,but the interaction mechanism with the hydroxyl radicals(OH·)that related to the food consumption,metabolism process and inflammation is unclear.The OH·simulation test showed that the optimal rate of Neu5Gc content decrease was 76.23%±2.17%at the conditions bellow,the amount of hydrogen peroxide(H2O2)was 2%and the 254 nm UV lamp was treated for 15 minutes.To explore the reaction mechanism,the density functional theory was used to optimize the station points and enthalpy correction of all one-step hydrogen abstraction channels of OH·on Neu5Gc hydroxyl hydrogen and non-hydroxy hydrogen at the theoretical level of M062X/6-31+G(d,p)in the gas phase,aqueous phase and benzene phase.The energy barrier was calculated at the level M062X/def2TZVP.Reaction rates and kinetic parameters were obtained in the 298 K^453 K range by the transition state theory and the three-parameter Arrhenius equation.Theoretical calculations showed that the minimum hydrogen extraction energy barrier occurred at the H 24 position of Neu5Gc under the gas and benzene phase with 13.20 kJ/mol and 19.54 kJ/mol,respectively,the lowest energy barrier in the aqueous phase was 6.25 kJ/mol at H 29 position.For the lowest activation energy,in the gas phase was 8.09 kJ/mol at the H 39 position,in the benzene phase was 1.78 kJ/mol at the H 38 position,in the aqueous phase was 14.3 kJ/mol at the H 24 position.In the range of 273 to 453 K,the hydrogen extraction rate of the non-hydroxyl hydrogen in the Neu5Gc molecule can be up to 108 times higher than that of the hydroxyl hydrogen.In summary,the interaction mechanism of OH·with Neu5Gc was mainly through the hydrogen extraction of Neu5Gc non-hydroxyl hydrogen atoms.