DFT探究番茄红素清除单线态氧的机理

发布时间：2018-06-16 02:44

本文选题：番茄红素 + 抗氧化　；参考：《河南师范大学》2017年硕士论文

【摘要】：番茄红素属于类胡萝卜素的一种,在水果和蔬菜中广泛分布,是目前自然界中抗氧化能力最强的天然食品成分。番茄红素具有许多优秀的生理活性,表现在对低密度脂蛋白(LDL)的氧化以及HMG-CoA还原酶活性的抑制,影响胆固醇的生物合成,和降低人体血液中的甘油三脂和胆固醇的水平等等。其具有多个共轭双键的结构导致了番茄红素构型的多样化。在所有的顺反异构体中,全反式是番茄红素最主要的异构体形式。然而,无论顺式异构体还是全反式番茄红素,关于其清除单线态氧的机理尚没有明确的解释,这严重影响着番茄红素在其他领域的发展与应用。对于单线态氧来说,其在生物氧化过程中起着关键的作用,并且目前其危害已经超出于它对人们的益处,所以番茄红素猝灭单线态氧的研究已经引起不少学者专家的关注。本文利用密度泛函方法分别优化了基态和激发态的番茄红素以及氧的构型。关于番茄红素猝灭单线态氧的机理运行以及分析均是在B3LYP方法6-311+G(d,p)基组这一层面上进行。简单说来,番茄红素猝灭单线态氧是一个电子交换能量转移的过程,即单线态氧(处于激发态)释放能量变为三线态(基态),与此同时处于基态的番茄红素吸收能量并变为激发态。在猝灭过程中,电子的交换指的是两个分别来自番茄红素和单线态氧的自旋方向相反的电子进行的交换。根据能量和吉布斯自由能的计算,我们可以验证番茄红素猝灭单线态氧可以发生,并且是自发进行的。从能级和前线分子轨道的层面我们分析得到番茄红素和氧在电子交换的同时也进行着能量的转移和自旋的转变。此外,我们还可以得到猝灭过程中番茄红素和氧的电荷可以同时进行相互传递,不过,这种传递在不同的阶段分别以氧和番茄红素为主。总的来说,番茄红素和氧相近的能级、反应物前线分子轨道对称性的匹配、猝灭过程中体系内无电子自旋的翻转以及值较负的吉布斯自由能变,所有这些使得番茄红素猝灭单线态氧的过程顺利容易的进行。另外,本文还着重讨论了四种常见的番茄红素的顺式异构体,分别为5位、9位、13位以及15位的顺式异构体。同样在密度泛函理论的基础上利用B3LYP方法6-311+G(d,p)基组优化了番茄红素这四种常见的异构体,并相应进行了频率的计算。在此基础上,分别从能量、吉布斯自由能、相邻能量的比较等量子化学参数进行对比分析四种顺式异构体的相对稳定性的情况,同时验证了顺式番茄红素猝灭单线态氧的可能性。本文从理论上验证和分析了番茄红素猝灭单线态氧的机理,为番茄红素在食品、化学、医药产业以及其他领域的进一步发展奠定理论基础并提供理论支撑,但是猝灭的机理在实验方面还未得到证实。只有化学工作者坚持不懈的将番茄红素猝灭单线态氧的机理甚至清除体内其他自由基的机理弄明白、理清楚,番茄红素,作为有效的绿色的抗氧化剂,其潜在的价值才能真正得到有效准确的评估,其应用范围才会得到更进一步的延伸。
[Abstract]:Lycopene, a kind of carotenoid, is widely distributed in fruits and vegetables. It is the most powerful natural food ingredient in nature. Lycopene has many excellent physiological activities, which is manifested in the oxidation of low density lipoprotein (LDL) and the inhibition of the activity of HMG-CoA reductase, which affects the biosynthesis of cholesterol. And reducing the level of glycerol three and cholesterol in the blood of the human body and so on. Its structure with multiple conjugated double bonds leads to the diversity of lycopene configuration. In all the CIS trans isomers, all trans is the most important isomer of lycopene. However, the scavenging of the cis isomer or all trans lycopene There is no clear explanation for the mechanism of singlet oxygen, which seriously affects the development and application of lycopene in other fields. For the single state oxygen, it plays a key role in the biological oxidation process, and at present its harm is beyond its benefit to people. The study of the quenching of single line oxygen with lycopene has caused the study of the single line oxygen. In this paper, the density functional method is used to optimize the lycopene and the configuration of oxygen in the ground and excited states. The mechanism and analysis of the lycopene quenching of singlet oxygen are carried out on the basis of the B3LYP method 6-311+G (D, P) base group. The process of electron transfer energy transfer, that is, the release energy of the single state oxygen (in the excited state) becomes three linear states (the ground state), while the lycopene in the ground state absorbs energy and turns to the excited state. In the process of quenching, the exchange of electrons refers to the two electrons of the opposite spin direction from the Solanin and the single state oxygen respectively. Exchange. According to the calculation of energy and Gibbs's free energy, we can verify that lycopene quenches the singlet oxygen can occur and is spontaneous. From the level of energy and the frontline molecular orbital, we analyze the transfer of lycopene and oxygen in the electronic exchange and the transfer of energy and spin. In addition, we The charge of lycopene and oxygen can be transmitted simultaneously during the quenching process. However, this transfer is dominated by oxygen and lycopene at different stages. In general, the similar level of lycopene and oxygen, the matching of the symmetry of the frontline molecular orbital of the reactant, and the no electron spin in the system during the quenching process. In this paper, four common lycopene cis isomers, which are 5, 9, 13, and 15 cis isomers, are also discussed in this paper. And B is also used on the basis of density functional theory (B). The 3LYP method 6-311+G (D, P) base group optimized the four common isomers of lycopene and calculated the frequency correspondingly. On this basis, the relative stability of four cis isomers was compared and analyzed from energy, Gibbs free energy, and the comparison of adjacent energy, and the CIS type tomato was verified. The possibility of quenching the single line oxygen by erythropoietin. This paper theoretically verified and analyzed the mechanism of lycopene quenching of single line oxygen, which laid the theoretical foundation for the further development of lycopene in food, chemistry, pharmaceutical industry and other fields, but the mechanism of quenching has not been confirmed in the experiment. Only the mechanism of the quenching is not confirmed in the experiment. It is clear that the potential value of lycopene, as an effective green antioxidant, can be effectively and accurately evaluated, and the scope of its use will be further extended.
【学位授予单位】：河南师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O629.4

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